Main Illustrated Medical Dictionary : Essential A-Z Quick Reference to over 5,500 Medical Terms
Report a problemThis book has a different problem? Report it to us
Check Yes if Check Yes if Check Yes if Check Yes if
you were able to open the file
the file contains a book (comics are also acceptable)
the content of the book is acceptable
Title, Author and Language of the file match the book description. Ignore other fields as they are secondary!
Check No if Check No if Check No if Check No if
- the file is damaged
- the file is DRM protected
- the file is not a book (e.g. executable, xls, html, xml)
- the file is an article
- the file is a book excerpt
- the file is a magazine
- the file is a test blank
- the file is a spam
you believe the content of the book is unacceptable and should be blocked
Title, Author or Language of the file do not match the book description. Ignore other fields.
Change your answer
You may be interested in Powered by Rec2Me
Most frequent terms
nice library i get best best book for me i don't have word b/c i live in remote area top happier to me thanks to Z-library
27 June 2019 (19:47)
Plenty books to choose from
07 July 2019 (03:10)
Thumbs up! Thanks a lot.
07 July 2019 (11:12)
Fantastic book useful and easy
27 July 2019 (21:34)
Best bookstore website ever and ever.Thank you very much for your full support on us as Medical professionals,every book i missed for long is here even more than I expected.
07 August 2019 (01:08)
you are my live saver. thank for books, esp the medical book which I hardy to find in my country or it is too expensive for physical books. love you guys.
20 August 2019 (04:28)
Best Book I've ever read.
27 August 2019 (08:24)
Thank you, you guys are the best.
04 October 2019 (06:18)
Thumps up! Thanks for your sharing.
02 November 2019 (16:10)
really gratefull for you
20 November 2019 (13:40)
Thank you for sharing this
02 December 2019 (08:52)
thank you for everthing
12 December 2019 (15:04)
Thank you this helped me so much !
27 February 2020 (09:51)
Thank You, you guys are helping me a lot. i live in small area where there is no good bookstore. in fact, i'm broke too.
28 February 2020 (10:00)
this is a good source of medical books for poor countries -my best regards for your help
28 June 2020 (12:21)
The British Medical Association ILLUSTRATED MEDICAL DICTIONARY CORONARY ARTERY Superior vena cava Pulmonary veins Right main coronary artery Aorta Left main coronary artery Left circumflex artery Left anterior descending artery Coronary vein Inferior vena cava Descending aorta coronary Any structure that encircles like a crown. The term usually refers to the coronary arteries encircling the heart. It is also sometimes used as a nonmedical term for a heart attack (see myocardial infarction). coronary artery Either of the 2 main arteries that supply the tissues of the heart with oxygen-rich blood. These arteries, known as the left and right main coronary arteries, arise directly from the aorta. The term coronary artery is also applied to any of the arteries that branch off from the main coronary arteries, such as the left circumflex artery and the left anterior descending artery. Blockage of a coronary artery as a result of atherosclerosis can lead to myocardial infarction. (See also coronary artery disease.) Essential A–Z quick reference to over 5,500 medical terms The British Medical Association ILLUSTRATED MEDICAL DICTIONARY A Dorling Kindersley Book ABDOMEN A ABDOMINAL SWELLING intake, eating unwisely, or an attack of diarrhoea. Pain in the lower abdomen is common during menstruation but is occasionally due to a gynaecological disorder such as endometriosis. Cystitis is a common cause of pain or discomfort in the abdomen. Bladder distension as a result of urinary obstruction may also cause abdominal pain. Abdominal colic is pain that occurs every few minutes as one of the internal organs goes into muscular spasm in an attempt to overcome an obstruction such as a stone or an area of inflammation. The attacks of colic may become more severe and may be associated with vomiting (see abdomen, acute). Peptic ulcer often produces recurrent gnawing pain. Other possible causes of abdominal pain are infection, such as pyelonephritis, and ischaemia (lack of blood supply), as occurs when a volvul; us (twisting of the intestine) obstructs blood vessels. Tumours affecting an abdominal organ can cause pain. Abdominal pain can also result from anxiety. For mild pain, a wrapped hot-water bottle is often effective. Pain due to peptic ulcer can be temporarily relieved by food or by taking antacid drugs. Abdominal pain that is not relieved by vomiting, persists for more than 6 hours, or is associated with sweating or fainting requires urgent medical attention. Urgent attention is also necessary if pain is accompanied by persistent vomiting, vomiting of blood, or passing of bloodstained or black faeces. Unexplained weight loss or changes in bowel habits should always be investigated. Investigation of abdominal pain may include the use of imaging tests such as ultrasound scanning, and endoscopic examination in the form of gastroscopy, colonoscopy, or laparoscopy. abdominal swelling Enlargement of the abdomen. Abdominal swelling is a natural result of obesity and growth of the uterus during pregnancy. Wind in the stomach or intestine may cause uncomfortable, bloating distension of the abdomen. Some women experience abdominal distension due to temporary water retention just before menstruation. Other causes may be more serious. A abdomen The region of the body between the chest and the pelvis. The abdominal cavity is bounded by the ribs and diaphragm above, and by the pelvis below, with the spine and abdominal muscles forming the back, side, and front walls. It contains the liver, stomach, intestines, spleen, pancreas, and kidneys. In the lower abdomen, enclosed by the pelvis, are the bladder, rectum, and, in women, the uterus and ovaries. ABDOMEN Stomach Liver Large intestine Area of abdomen Small intestine Rectum abdomen, acute Persistent, severe abdominal pain of sudden onset, usually associated with spasm of the abdominal muscles, vomiting, and fever. The most common cause of an acute abdomen is peritonitis. Other causes include appendicitis, abdominal injury, perforation of an internal organ due to disorders such as peptic ulcer or diverticular disease. Acute abdominal pain commonly begins as a vague pain in the centre but then becomes localized. An acute abdomen requires urgent medical investigation that may involve a laparoscopy or a laparotomy. Treatment depends on the underlying cause. abdominal pain Discomfort in the abdomen. Mild abdominal pain is common and is often due to excessive alcohol 4 ABDOMINAL THRUST ABSCESS For instance, ascites (accumulation of fluid between organs) may be a symptom of cancer or disease of the heart, kidneys, or liver; swelling may also be due to intestinal obstruction (see intestine, obstruction of) or an ovarian cyst. Diagnosis of the underlying cause may involve abdominal X-rays, ultrasound scanning, laparotomy, or laparoscopy. In ascites, some fluid between organs may be drained for examination. abdominal thrust A first-aid treatment for choking, in which sharp upward pressure is applied to the upper abdomen to dislodge a foreign body obstructing the airway. The technique is also known as the Heimlich manoeuvre. abdominal X-ray An X-ray examination of the abdominal contents. X-rays can show whether any organ is enlarged and can detect swallowed foreign bodies in the digestive tract. They also show patterns of fluid and gas: distended loops of bowel containing fluid often indicate an obstruction (see intestine, obstruction of); gas outside the intestine indicates intestinal perforation. Calcium, which is opaque to X-rays, is present in most kidney stones (see calculus, urinary tract) and in some gallstones and aortic aneurysms; these can sometimes be detected on an abdominal X-ray. abducent nerve The 6th cranial nerve. It supplies the lateral rectus muscle of each eye, which is responsible for moving the eyeball outwards. The nerve originates in the pons (part of the brainstem) and passes along the base of the brain, entering the back of the eye socket through a gap between the skull bones. abduction Movement of a limb away from the central line of the body, or of a digit away from the axis of a limb. Muscles that carry out this movement are called abductors. (See also adduction.) ablation Removal or destruction of diseased tissue by excision (cutting away), cryosurgery (freezing), radiotherapy, diathermy (burning), or laser treatment. abnormality A physical deformity or malformation, a behavioural or mental problem, or a variation from normal in the structure or function of a cell, tissue, or organ in the body. ABO blood groups See blood groups. abortifacient An agent that causes abortion. In medical practice, abortion is induced using prostaglandin drugs, often given as vaginal pessaries. abortion In medical terminology, either spontaneous abortion (see miscarriage) or medically induced termination of pregnancy (see abortion, induced). abortion, induced Medically induced termination of pregnancy. Abortion may be performed if continuation of the pregnancy would risk the woman’s life, if the mental or physical health of the woman or her existing children is at risk, or if there is a substantial risk of handicap to the baby. Depending on the stage of pregnancy, termination may be induced by using drugs or by the surgical technique of vacuum suction curettage, under either a general or local anaesthetic, during which the fetal and placental tissues are removed. Complications are rare. abrasion Also called a graze, a wound on the skin surface that is caused by scraping or rubbing. abrasion, dental The wearing away of tooth enamel, often accompanied by the erosion of dentine (the layer beneath the enamel) and cementum (the bonelike tissue that covers the tooth root), usually through too-vigorous brushing. Abraded areas are often sensitive to cold or hot food or drink, and a desensitizing toothpaste and/or protection with a bonding (see bonding, dental) agent or filling may be needed. abreaction In psychoanalysis, the process of becoming consciously aware of repressed (buried) thoughts and feelings. In Freudian theory, abreaction ideally occurs by way of catharsis. abscess A collection of pus formed as a result of infection by microorganisms, usually bacteria. Abscesses may develop in any organ and in the soft tissues beneath the skin in any area. Common sites include the armpit, breast (see breast abscess), groin, and gums (see abscess, dental). Rarer sites include the liver (see liver abscess) and the brain (see brain abscess). Common bacteria, such as staphylococci, are the usual cause of abscesses, 5 A A ABSCESS, DENTAL ACANTHOSIS NIGRICANS although fungal infections can cause them, and amoebae are an important cause of liver abscesses (see amoebiasis). Infectious organisms usually reach internal organs via the bloodstream, or they penetrate tissues under the skin through a wound. An abscess may cause pain, depending on where it occurs. Most larger abscesses cause fever, sweating, and malaise. Those that are close to the skin often cause obvious redness and swelling. Antibiotics, antifungal drugs, or amoebicides are usually prescribed as appropriate. Most abscesses also need to be drained (see drain, surgical), and in some cases a tube may be left in place to allow continuous drainage. Some abscesses burst and drain spontaneously. Occasionally, an abscess within a vital organ damages enough surrounding tissue to cause permanent loss of normal function, or even death. abscess, dental A pus-filled sac in the tissue around the root of a tooth. An abscess may occur when bacteria invade the pulp (the tissues in the central cavity of a tooth) as a result of dental caries, which destroys the tooth’s enamel and dentine, allowing bacteria to reach the pulp. Bacteria can also gain access to the pulp when a tooth is injured. The infection in the pulp then spreads into the surrounding tissue to form an abscess. Abscesses can also result from periodontal disease, in which bacteria accumulate in pockets that form between the teeth and gums. The affected tooth aches or throbs, and biting or chewing is usually extremely painful. The gum around the tooth is tender and may be red and swollen. An untreated abscess eventually erodes a sinus (channel) through the jawbone to the gum surface, where it forms a swelling known as a gumboil. As the abscess spreads, the glands in the neck and the side of the face may become swollen, and fever may develop. Treatment may consist of draining the abscess, followed by root-canal treatment of the affected tooth, but in some cases extraction of the tooth is necessary. Antibiotics are prescribed if the infection has spread beyond the tooth. ABSCESS, DENTAL Enamel Dentine Decay Gum Pulp Blood vessel Nerve Jawbone Abscess An abscess in a periodontal pocket can usually be treated by the dentist scraping away infected material. absence In medical terms, a temporary loss or impairment of consciousness that occurs in some forms of epilepsy, typically generalized absence (petit mal) seizures in childhood. absorption The process by which fluids or other substances are taken up by body tissues. The term is commonly applied to the uptake of the nutrients from food into blood and lymph from the digestive tract. The major site of absorption is the small intestine, which is lined with microscopic finger-like projections called villi (see villus). The villi greatly increase the surface area of the intestine, thereby increasing the rate of absorption. acanthosis nigricans A rare condition in which thickened dark patches of skin appear in the groin, armpits, neck, and other skin folds. The condition may occur in young people as a genetic disorder or as the result of an endocrine disorder such as Cushing’s syndrome. It also occurs in people with carcinomas of the lung and other organs. Pseudoacanthosis nigricans is a much more common condition, usually seen in dark-complexioned people who are overweight. In this form, the skin in fold areas is both thicker and darker than the surrounding skin, and there is usually excessive sweating in affected areas. The condition may improve with weight loss. 6 ACARBOSE ACETYLCHOLINESTERASE INHIBITORS more difficult and results in a form of longsightedness called presbyopia. acebutolol A beta-blocker drug used to treat hypertension, angina pectoris, and certain types of arrhythmia in which the heart beats too rapidly. ACE inhibitor drugs A group of vasodilator drugs used to treat heart failure, hypertension, and diabetic nephropathy. ACE (angiotensin converting enzyme) inhibitors are often prescribed with other drugs such as diuretic drugs or betablocker drugs. Possible side effects include nausea, loss of taste, headache, dizziness, and dry cough. acetaminophen An analgesic drug more commonly known as paracetamol. acetazolamide A drug that is used in the treatment of glaucoma and, occasionally, to prevent or treat symptoms of mountain sickness. Possible adverse effects include lethargy, nausea, diarrhoea, and impotence. acetic acid The colourless, pungent, organic acid that gives vinegar its sour taste. In medicine, acetic acid is an ingredient of antiseptic gels that are used for certain vaginal infections. acetylcholine A type of neurotransmitter (a chemical that transmits messages between nerve cells or between nerve and muscle cells). Acetylcholine is the neurotransmitter found at all nervemuscle junctions and at many other sites in the nervous system. The actions of acetylcholine are called cholinergic actions, and these can be blocked by anticholinergic drugs. acetylcholinesterase inhibitors A group of drugs that are used in the treatment of mild to moderate dementia due to Alzheimer’s disease, in which there is a deficiency of the neurotransmitter acetylcholine in the brain. acarbose A drug that is used to treat type 2 diabetes mellitus. Acarbose acts on enzymes in the intestines, inhibiting the digestion of starch and therefore slowing the rise in blood glucose levels after a carbohydrate meal. accessory nerve The 11th cranial nerve. Unlike the other cranial nerves, most of the accessory nerve originates from the spinal cord. The small part of the nerve that originates from the brain supplies many muscles of the palate, pharynx (throat), and larynx (voice box). Damage to this part of the nerve may cause difficulty in speaking and swallowing. The spinal part of the nerve supplies large muscles of the neck and back, notably the sternomastoid and trapezius. Damage to the spinal fibres of the nerve paralyses these muscles. accidental death Death that occurs as a direct result of an accident. A high proportion of deaths in young adults, particularly among males, are accidental. Many of these deaths are due to road traffic accidents, drowning, or drug overdose. Falls in the home and burning or asphyxiation due to fire are common causes of accidental death in elderly people. Fatal accidents at work have become less common with the introduction of effective safety measures. accommodation Adjustment, especially the process by which the eye adjusts itself to focus on near objects. At rest, the eye is focused for distant vision, when its lens is thin and flat. To make focusing on a nearer object possible, the ciliary muscle of the eye contracts, which reduces the pull on the outer rim of the lens, allowing it to become thicker and more convex. With age, the lens loses its elasticity. This makes accommodation more and ACCOMMODATION Light rays from near object Ciliary muscle Point of focus NEAR FOCUS Light rays from distant object Rounded lens bends the light Ciliary muscle 7 Point of focus DISTANT FOCUS Flattened lens A A ACETYLCYSTEINE ACID–BASE BALANCE Drugs such as donepezil and rivastigmine work by blocking the action of acetylcholinesterase, the enzyme in the brain responsible for the breakdown of acetylcholine. This raises acetylcholine levels, and, in half of all patients, the drugs slow the rate of progression of dementia. They have no effect on dementia due to other causes, such as stroke or head injury, however. Common side effects include nausea, dizziness, and headache. Rarely, difficulty in passing urine may occur. acetylcysteine A drug used in the treatment of paracetamol overdose and as a mucolytic drug to loosen sputum. When the drug is taken in large doses, vomiting or rash may occur as rare side effects. achalasia A rare condition of unknown cause in which the muscles at the lower end of the oesophagus and the sphincter (valve) between the oesophagus and the stomach fail to relax to let food into the stomach after swallowing. As a result, the lowest part of the oesophagus is narrowed and becomes blocked with food, while the part above widens. Symptoms include difficulty and pain with swallowing and pain in the lower chest and upper abdomen. A barium swallow (a type of barium X-ray examination) and gastroscopy may be performed to investigate achalasia. ACHILLES TENDON Violent stretching of the tendon can cause it to rupture; in such cases, surgical repair may be necessary. achlorhydria Absence of stomach acid secretions. This may be due to chronic atrophic gastritis or to an absence or malfunction of acid-producing parietal cells in the stomach lining. Achlorhydria may not produce symptoms but is associated with stomach cancer, however, and is a feature of pernicious anaemia (see anaemia, megaloblastic). achondroplasia A rare genetic disorder of bone growth that leads to short stature. The condition is caused by a dominant gene (see genetic disorders) but often arises as a new mutation. The long bones of the arms and legs are affected mainly. The cartilage that links each bone to its epiphysis (the growing area at its tip) is converted to bone too early, preventing further limb growth. Those affected have short limbs, a welldeveloped trunk, and a head of normal size except for a protruding forehead. aciclovir An antiviral drug that can be taken by mouth, used topically, or given intravenously to reduce the severity of viral infections including herpes simplex and herpes zoster. Local adverse reactions commonly occur after topical use. Other side effects are uncommon but can include nausea and vomiting. acid A substance defined as a donor of hydrogen ions (hydrogen atoms with positive electrical charges). Acid molecules, when mixed with or dissolved in water, split up to release their constituent ions; all acids release hydrogen as the positive ion. (See also acid–base balance; alkali.) acid–base balance A combination of mechanisms that ensures that the body’s fluids are neither too acid nor too alkaline (alkalis are also called bases). The body has three mechanisms for maintaining normal acid–base balance: buffers, breathing, and the activities of the kidneys. Buffers are substances in the blood that neutralize acid or alkaline wastes. Rapid breathing results in the blood becoming less acidic; slow breathing has the opposite effect. The kidneys regulate the amounts of acid or alkaline wastes in the urine. Oesophageal dilatation allows the oesophagus to be widened for long periods. Surgery to cut some of the muscles at the stomach entrance may be necessary. Achilles Achilles tendon tendon The tendon that raises the heel. The Achilles tendon is formed from the calf muscles (gastrocnemius, Heel soleus, and plantar muscles) and is attached to the calcaneus (heel-bone). Minor injuries to the Achilles tendon are common and can result in inflammation (tendinitis). Calf muscle 8 ACIDOSIS ACOUSTIC NEUROMA Disturbances of the body’s acid–base balance result in either acidosis (excessive blood acidity) or alkalosis (excessive blood alkalinity). acidosis A disturbance of the body’s acid–base balance in which there is an accumulation of acid or loss of alkali (base). There are 2 types of acidosis: metabolic and respiratory. One form of metabolic acidosis is ketoacidosis, which occurs in uncontrolled diabetes mellitus and starvation. Metabolic acidosis may also be caused by loss of bicarbonate (an alkali) as a result of severe diarrhoea. In kidney failure, there is insufficient excretion of acid in the urine. Respiratory acidosis occurs if breathing fails to remove enough carbon dioxide from the lungs. The excess carbon dioxide remains in the bloodstream, where it dissolves to form carbonic acid. Impaired breathing leading to respiratory acidosis may be due to chronic obstructive pulmonary disease (see pulmonary disease, chronic obstructive), bronchial asthma, or airway obstruction. acid reflux Regurgitation of acidic fluid from the stomach into the oesophagus due to inefficiency of the muscular valve at the lower end of the oesophagus. Also known as gastro-oesophageal reflux disease (GORD), acid reflux may inflame the oesophagus, resulting in heartburn due to oesophagitis. It may occur in pregnancy and often affects overweight people. acne A chronic skin disorder caused by inflammation of the hair follicles and sebaceous glands in the skin. The most common type is acne vulgaris, which almost always develops during puberty. Acne spots are caused by the obstruction of hair follicles by sebum (the oily substance secreted by the sebaceous glands). Bacteria multiply in the follicle, causing inflammation. The change in sebum secretion at puberty seems to be linked with increased levels of androgen hormones (male sex hormones). Acne may be brought on or aggravated by drugs such as corticosteroids and androgens. Exposure to certain chemicals and oils in the workplace can also cause a type of acne. A Acne develops in areas of skin with a high concentration of sebaceous glands, mainly the face, centre of the chest, upper back, shoulders, and around the neck. Milia (whiteheads), comedones (blackheads), nodACNE ules (firm swellings beneath the Sebaceous Inflamed skin skin), and cysts gland Plug (larger, fluid-filled Pus swellings) are the Hair most commonly occurring spots. Some, particularly cysts, leave scars after they heal. There is no instant cure for acne, but washing the affected areas at least twice daily may help to keep ACNE SPOT it under control. Topical drug treatments, such as benzoyl peroxide or retinoic acid, unblock the pores and promote healing. Ultraviolet light can be beneficial. If topical treatment has failed, oral drug treatment with antibiotics, hormones, or isotretinoin may be given. Acne improves slowly over time, often clearing up by the end of the teenage years. acoustic nerve The part of the vestibulocochlear nerve (the 8th cranial nerve) that is concerned with hearing. It is also known as the auditory nerve. acoustic neuroma A rare, noncancerous tumour arising from supporting cells that surround the 8th cranial nerve (see acoustic nerve), usually within the internal auditory meatus (the canal in the skull through which the nerve passes from the inner ear to the brain). Usually, the cause of an acoustic neuroma is unknown. However, tumours that affect the nerves on both sides of the head simultaneously may be part of a condition known as neurofibromatosis. Acoustic neuroma can cause deafness, tinnitus, loss of balance, and pain in the face and the affected ear. Diagnosis is made by hearing tests followed by X-rays, CT scanning, or MRI. Surgery may be needed, but treatment 9 A ACROCYANOSIS ACTINOMYCOSIS with radiotherapy to shrink the tumour is also effective. acrocyanosis A circulatory disorder in which the hands and feet turn blue, may become cold, and sweat excessively. Acrocyanosis is caused by spasm of the small blood vessels and is often aggravated by cold weather. It is related to Raynaud’s disease. acrodermatitis enteropathica A rare inherited disorder in which areas of the skin (most commonly the fingers, toes, scalp, and the areas around the anus and mouth) are reddened, ulcerated, and covered with pustules. Acrodermatitis enteropathica is due to an inability to absorb enough zinc from food. Zinc supplements usually help. acromegaly A rare disease characterized by abnormal enlargement of the skull, jaw, hands, feet, and also of the internal organs. It is caused by excessive secretion of growth hormone from the anterior pituitary gland at the base of the brain and is the result of a pituitary tumour. A tumour that develops before puberty results in gigantism. Acromegaly is diagnosed by measuring blood levels of growth hormone, followed by CT scanning or MRI. acromioclavicular joint The joint that lies between the outer end of the clavicle (collarbone) and the acromion (the bony prominence at the top of the scapula (shoulderblade). acroparaesthesia A medical term used to describe tingling in the fingers or toes (see pins-and-needles). ACTH The common abbreviation for adrenocorticotrophic hormone (also called corticotrophin). ACTH is produced by the anterior pituitary gland and stimulates the adrenal cortex (outer layer of the adrenal glands) to release various corticosteroid hormones, most importantly hydrocortisone (cortisol) but also aldosterone and androgen hormones. ACTH production is controlled by a feedback mechanism involving both the hypothalamus and the level of hydrocortisone in the blood. ACTH levels increase in response to stress, emotion, injury, infection, burns, surgery, and decreased blood pressure. A tumour of the pituitary gland can cause excessive ACTH production which leads to overproduction of hydrocortisone by the adrenal cortex, resulting in Cushing’s syndrome. Insufficient ACTH production results in decreased production of hydrocortisone, causing low blood pressure. Synthetic ACTH is occasionally given by injection to treat arthritis or allergy. actin A protein involved in muscle contraction, in which microscopic filaments of actin and another protein, myosin, slide in between each other. acting out Impulsive actions that may reflect unconscious wishes. The term is most often used by psychotherapists to describe behaviour during analysis when the patient “acts out” rather than reports fantasies, wishes, or beliefs. Acting out can also occur as a reaction to frustrations encountered in everyday life, often taking the form of antisocial, aggressive behaviour. actinic Pertaining to changes caused by the ultraviolet rays in sunlight, as in actinic dermatitis (inflammation of the skin) and actinic keratosis (roughness and thickening of the skin). actinomycosis An infection caused by ACTINOMYCES ISRAELII or related actinomycete bacteria. The most common form of actinomycosis affects the jaw area. A painful swelling appears and pus discharges through small openings that develop in the skin. Another form ACROMIOCLAVICULAR JOINT Clavicle Acromioclavicular joint Acromion Scapula Humerus acromion A bony prominence at the top of the scapula (shoulderblade). The acromion articulates with the end of the clavicle (collarbone) to form the acromioclavicular joint. 10 ACUITY, VISUAL ADENOCARCINOMA of actinomycosis affects the pelvis in women, causing lower abdominal pain and bleeding between periods. This form was associated with a type of IUD, no longer in use, that did not contain copper. Rarely, forms of the disorder affect the appendix or lung. Actinomycosis is treated with antibiotics. acuity, visual See visual acuity. acupressure A derivative of acupuncture in which pressure is applied instead of needles. acupuncture A branch of Chinese medicine in which needles are inserted into a patient’s skin as therapy for various disorders or to induce anaesthesia. Traditional Chinese medicine maintains that the chi (life-force) flows through the body along channels called meridians. A blockage in one or more of these meridians is thought to cause ill health. Acupuncturists aim to restore health by inserting needles at appropriate sites along the affected meridians. The needles are stimulated by rotation or by an electric current. Acupuncture has been used successfully as an anaesthetic for surgical procedures and to provide pain relief after operations and for chronic conditions. acute A term often used to describe a disorder or symptom that develops suddenly. Acute conditions may or may not be severe, and they are usually of short duration. (See also chronic.) Adam’s apple A projection at the front of the neck, just beneath the skin, that is formed by a prominence on the thyroid cartilage, which is part of the larynx (voice box). The Adam’s apple enlarges in males at puberty. ADD The abbreviation for attention deficit disorder, more commonly known as the corticosteroid hormones hydrocortisone and aldosterone, normally produced by the adrenal cortex (the outer part of the adrenal glands). Excessive amounts of ACTH are secreted by the pituitary gland in an attempt to increase output of the corticosteroid hormones. Secretion and activity of another hormone, melanocyte stimulating hormone (MSH), is also increased. Addison’s disease can be caused by any disease that destroys the adrenal cortices. The most common cause is an autoimmune disorder in which the immune system produces antibodies that attack the adrenal glands. Symptoms generally develop gradually over months or years, and include tiredness, weakness, abdominal pain, and weight loss. Excess MSH may cause darkening of the skin in the creases of the palms, pressure areas of the body, and the mouth. Acute episodes, called Addisonian crises, brought on by infection, injury, or other stresses, can also occur. The symptoms of these include extreme muscle weakness, dehydration, hypotension (low blood pressure), confusion, and coma. Hypoglycaemia (low blood glucose) also occurs. Life-long corticosteroid drug treatment is needed. Treatment of Addisonian crises involves rapid infusion of saline and glucose, and supplementary doses of corticosteroid hormones. adduction Movement of a limb towards the central line of the body, or of a digit towards the axis of a limb. Muscles that carry out this movement are often called adductors. (See also abduction.) adenitis Inflammation of lymph nodes. Cervical adenitis (swelling and tenderness of the lymph nodes in the neck) occurs in certain bacterial infections, especially tonsillitis, and glandular fever (see infectious mononucleosis). Mesenteric lymphadenitis is inflammation of the lymph nodes inside the abdomen and is usually caused by viral infection. Treatment of adenitis may include analgesic drugs, and antibiotic drugs if there is a bacterial infection. adenocarcinoma The technical name for a cancer of a gland or glandular tissue, or for a cancer in which the cells attention deficit hyperactivity disorder. addiction Dependence on, and craving for, a particular drug, for example alcohol, diazepam (a tranquillizer), or heroin. Reducing or stopping intake of the drug may lead to characteristic physiological or psychological symptoms (see withdrawal syndrome), such as tremor or anxiety. (See also alcohol dependence; drug dependence.) Addison’s disease A rare chronic disorder in which there is a deficiency of 11 A A ADENOIDECTOMY ADIPOSE TISSUE form gland-like structures. An adenocarcinoma arises from epithelium (the layer of cells that lines the inside of organs). Cancers of the colon, breast, pancreas, and kidney are usually adenocarcinomas, as are some cancers of the cervix, oesophagus, salivary glands, and other organs. (See also intestine, cancer of; kidney cancer; pancreas, cancer of.) adenoidectomy Surgical removal of the adenoids. An adenoidectomy is usually performed on a child with abnormally large adenoids that are causing recurrent infections of the middle ear or air sinuses. The operation may be performed together with tonsillectomy. adenoids A mass of glandular tissue at the back of the nasal passage above the tonsils. The adenoids are made up of lymph nodes, which form part of the body’s defences against upper respiratory tract infections; they tend to enlarge during early childhood, a time when such infections are common. organs). Adenomas of endocrine glands can cause excessive hormone production, leading to disease. For example, pituitary gland adenomas can result in acromegaly or Cushing’s syndrome. adenomatosis An abnormal condition of glands in which they are affected either by hyperplasia (overgrowth) or the development of numerous adenomas (noncancerous tumours). Adenomatosis may simultaneously affect 2 or more different endocrine glands. ADH The abbreviation for antidiuretic hormone (also called vasopressin), which is released from the posterior part of the pituitary gland and acts on the kidneys to increase their reabsorption of water into the blood. ADH reduces the amount of water lost in the urine and helps to control the body’s overall water balance. ADH production is controlled by the hypothalamus. Various factors can affect ADH production and thus disturb the body’s water balance, including drinking alcohol, the disorder diabetes insipidus, or a major operation. ADHD The abbreviation for attention deficit hyperactivity disorder. adhesion The joining of normally unconnected body parts by bands of fibrous tissue. Adhesions are sometimes present from birth, but they most often develop as a result of scarring after inflammation. Adhesions are most common in the abdomen, where they often form after peritonitis (inflammation of the abdominal lining) or surgery. Sometimes, loops of intestine are bound together by adhesions, causing intestinal obstruction (see intestine, obstruction of). In such cases, surgery is usually required to cut the bands of tissue. adipose tissue A layer of fat just beneath the skin and around various internal organs. Adipose tissue is built up from fat deposited as a result of excess food intake, thus acting as an energy store; excessive amounts of adipose tissue produce obesity. The tissue insulates against loss of body heat and helps absorb shock in areas subject to sudden or frequent pressure, such as the buttocks of feet. In men, superficial adipose tissue accumulates around the shoulders, waist, ADENOIDS Adenoids Nasal cavity Opening of eustachian tube Pharynx Tongue Tonsils In most children, adenoids shrink after the age of about 5 years, disappearing altogether by puberty. In some children, however, they enlarge, obstructing breathing and blocking the eustachian tubes, which connect the middle ear to the throat. This results in recurrent infections and deafness. Infections usually respond to antibiotic drugs, but if they recur frequently, adenoidectomy may be recommended. adenoma A noncancerous tumour or cyst that resembles glandular tissue and arises from the epithelium (the layer of cells that lines the inside of 12 ADJUVANT ADRENAL GLAND DISORDERS and abdomen; in women, it occurs on the breasts, hips, and thighs. adjuvant A substance that enhances the action of another substance in the body. The term is usually used to describe an ingredient added to a vaccine to increase the production of antibodies by the immune system, thus enhancing the vaccine’s effect. Adjuvant chemotherapy is the use of anticancer drugs in addition to surgical removal of a tumour. Adlerian theory The psychoanalytical ideas set forth by the Austrian psychiatrist Alfred Adler. Also called individual psychology, Adler’s theories were based on the idea that everyone is born with feelings of inferiority. Life is seen as a constant struggle to overcome these feelings; failure to do so leads to neurosis. (See also psychoanalytic theory.) adolescence The period between childhood and adulthood, which broadly corresponds to the teenage years. Adolescence commences and overlaps with, but is not the same as, puberty. ADP The abbreviation for adenosine diphosphate, the chemical that takes up energy released during biochemical reactions to form ATP (adenosine triphosphate), the body’s main energy-carrying chemical. When ATP releases its energy, ADP is reformed. (See also metabolism.) adrenal failure Insufficient production of hormones by the adrenal cortex (the outer part of the adrenal glands). It can be acute or chronic. Adrenal failure may be caused by a disorder of the adrenal glands, in which case it is called Addison’s disease, or by reduced stimulation of the adrenal cortex by ACTH, a hormone produced by the pituitary gland. adrenal glands A pair of small, triangular endocrine glands located above the kidneys. Each adrenal gland has 2 distinct parts: the outer cortex and the smaller, inner medulla. The cortex secretes aldosterone, which, together with hydrocortisone and corticosterone and small amounts of androgen hormones helps to maintain blood pressure. Hydrocortisone controls the body’s use of fats, proteins, and carbohydrates and is also important in helping the body to cope with stress. Hydrocortisone and corticosterone also suppress inflammatory reactions and some activities of the immune system. Production of adrenal cortical hormones is controlled by ACTH, which is produced in the pituitary gland. The adrenal medulla is part of the sympathetic autonomic nervous system. In response to stress, it secretes the hormones adrenaline (epinephrine) and noradrenaline (norepinephrine), which increase heart-rate and blood flow. A ADRENAL GLANDS Adrenal gland Kidney Adrenal cortex Adrenal medulla LOCATION Blood vessel Kidney STRUCTURE OF ADRENAL GLAND adrenal gland disorders A range of uncommon but sometimes serious disorders due to deficient or excessive production of hormones by one or both of the adrenal glands. A genetic defect causes congenital adrenal hyperplasia, in which the adrenal cortex is unable to make sufficient hydrocortisone and aldosterone, and androgens are produced in excess. In adrenal failure, there is also deficient production of hormones by the adrenal cortex; if due to disease of the adrenal glands, it is called Addison’s disease. Adrenal tumours are rare and generally lead to excess hormone production. In many cases, disturbed activity of the adrenal glands is caused, not by disease of the glands themselves, but by an increase or decrease in the blood level of hormones that influence the action of the adrenal glands. For example, hydrocortisone production by the adrenal cortex is controlled by ACTH, which is secreted by the pituitary gland. Pituitary disorders can disrupt production of hydrocortisone. 13 Fat A ADRENAL HYPERPLASIA, CONGENITAL AFFECT phaeochromocytoma and neuroblastoma, adrenal hyperplasia, congenital An uncommon genetic disorder in which an enzyme defect blocks the production of corticosteroid hormones from the adrenal glands. Excessive amounts of androgens (male sex hormones) are produced, which can result in abnormal genital development in an affected fetus. Other effects include dehydration, weight loss, low blood pressure, and hypoglycaemia. Hyperplasia (enlargement) of the adrenal glands occurs and there is excessive skin pigmentation in skin creases and around the nipples. In severe cases, the disorder is apparent soon after birth. In milder cases, symptoms appear later, sometimes producing premature puberty in boys and delayed menstruation, hirsutism, and potential infertility in girls. Congenital adrenal hyperplasia is confirmed by measuring corticosteroid hormones in blood and urine. Treatment is by hormone replacement. If this is started early, normal sexual development and fertility usually follow. adrenaline A hormone, also called epinephrine, released by the adrenal glands in response to signals from the sympathetic autonomic nervous system. These signals are triggered by stress, exercise, or by an emotion such as fear. Adrenaline increases the speed and force of the heartbeat. It widens the airways to improve breathing and narrows blood vessels in the skin and intestine so that an increased flow of blood reaches the muscles. Synthetic adrenaline is sometimes given by injection as an emergency treatment for cardiac arrest or anaphylactic shock. Adrenaline eye drops may be used to treat glaucoma, but regular use can cause a burning pain in the eye. adrenal tumours Cancerous or noncancerous tumours in the adrenal glands, usually causing excess secretion of hormones. Adrenal tumours are rare. Tumours of the adrenal cortex may secrete aldosterone, causing primary aldosteronism, or hydrocortisone, causing Cushing’s syndrome. Tumours of the medulla may cause excess secretion of adrenaline and noradrenaline. Two types of tumour affect the medulla: which affects children. These tumours cause intermittent hypertension and sweating attacks. Surgical removal of a tumour usually cures these conditions. adrenocorticotrophic hormone See ACTH. adrenogenital syndrome See adrenal hyperplasia, congenital. aerobic Requiring oxygen to live, function, and grow. Humans and many other forms of life are dependent on oxygen for “burning” foods to produce energy (see metabolism). In contrast, many bacteria thrive without oxygen and are described as anaerobic. aerobics Exercises, such as swimming and cycling, that allow muscles to work at a steady rate with a constant, adequate supply of oxygen-carrying blood, and that can therefore be sustained for long periods. Oxygen is used to release energy from the body’s stores. To fuel aerobic exercise, the muscles use fatty acid, burning it completely to produce energy, carbon dioxide, and water. When performed regularly, aerobic exercises improve stamina and endurance. They encourage the growth of capillaries, improving blood supply to the cells. Aerobic exercises also improve body cells’ capacity to use oxygen and increase the amount of oxygen the body can use in a given time. The condition of the heart also improves. (See also exercise; fitness.) aerodontalgia Sudden pain in a tooth brought on by a change in surrounding air pressure. Flying at a high altitude in a lowered atmospheric pressure can cause a pocket of air in the dental pulp to expand and irritate the nerve in the root. Aerodontalgia is more likely if there are improperly fitting fillings or poorly filled root canals. aerophagy Excessive swallowing of air, which may occur during rapid eating or drinking or be caused by anxiety. aetiology The cause of a disease or the study of the various factors involved in causing a disease. affect A term used to describe a person’s mood. The 2 extremes of affect are elation and depression. A person who experiences extreme moods or changes 14 AFFECTIVE DISORDERS AGGREGATION, PLATELET in moods may have an affective disorder. Shallow or reduced affect may be a sign of schizophrenia or of an organic brain syndrome. affective disorders Mental illnesses characterized predominantly by marked changes in affect. Mood may vary over a period of time between mania (extreme elation) and severe depression. (See also manic–depressive illness.) affinity A term used to describe the attraction between chemicals that causes them to bind together, as, for example, between an antigen and an antibody (see immune response). In microbiology, affinity describes physical similarity between organisms. In psychology, it refers to attraction between 2 people. aflatoxin A poisonous substance produced by ASPERGILLUS FLAVUS moulds, which contaminate stored foods, especially grains, peanuts, and cassava. Aflatoxin is believed to be one of the factors responsible for the high incidence of liver cancer in tropical Africa. afterbirth The common name for the tissues that are expelled from the uterus after delivery of a baby. The afterbirth includes the placenta and the membranes that surrounded the fetus. afterpains Contractions of the uterus that continue after childbirth. Afterpains are normal and are experienced by many women, especially during breastfeeding. They usually disappear a few days following the birth but may require treatment with analgesic drugs. agammaglobulinaemia A type of immunodeficiency disorder in which there is almost complete absence of B-lymphocytes and immunoglobulins in the blood. agar An extract of certain seaweeds with similar properties to gelatine. It can be taken for constipation to soften and give bulk to faeces, and to relieve indigestion and heartburn. Agar is also used as a gelling agent in media for bacterial cultures. age The length of time a person has existed. Of medical significance in diagnosis and in determining treatment, a person’s age is usually measured chronologically, but it can also be measured in terms of physical, mental, or developmental maturity. The age of a fetus is measured in terms of gestational age, which can be assessed accurately by ultrasound scanning. In children, the most useful measure of physical development is bone age (degree of bone maturity as seen on an X-ray) because all healthy individuals reach the same adult level of skeletal maturity, and each bone passes through the same sequence of growth. Dental age, another measure of physical maturity, can be assessed by the number of teeth that have erupted (see eruption of teeth) or by the amount of dental calcification (as seen on an X-ray) compared with standard values. In adults, physical age is difficult to assess other than by physical appearance. It can be estimated after death by the state of certain organs. Mental age can be assessed by comparing scores on intelligence tests with standards for chronological age. A young child’s age can be expressed in terms of the level of developmental skills, manual dexterity, language, and social skills. agenesis The complete absence at birth of an organ or bodily component, caused by failure of development in the embryo. agent Any substance or force capable of bringing about a biological, chemical, or physical change. (See also reagent.) Agent Orange A herbicide of which the major constituent is the phenoxy acid herbicide 2,4,5 T. This substance may be contaminated in manufacture with the highly toxic TCDD, commonly known as dioxin (see defoliant poisoning). age spots Blemishes that appear on the skin with increasing age. Most common are seborrhoeic keratoses, which are brown or yellow, slightly raised spots that can occur at any site. Also common in elderly people are freckles, solar keratoses (small blemishes caused by overexposure to the sun), and De Morgan’s spots, which are red, pinpoint blemishes on the trunk. Treatment is usually unnecessary for any of these, apart from solar keratoses, which may eventually progress to skin cancer. ageusia The lack or an impairment of the sense of taste (see taste, loss of). aggregation, platelet The clumping together of platelets (small, sticky blood 15 A A AGGRESSION AGUE alcohol withdrawal. Depression may be accompanied by agitation. agnosia An inability to recognize objects despite adequate sensory information about them reaching the brain via the eyes or ears or through touch. Agnosia is caused by damage to areas of the brain that are involved in interpretative and recall functions. The most common causes of this kind of damage are stroke or head injury. Agnosia is usually associated with just one of the senses of vision, hearing, or touch and is described as visual, auditory, or tactile respectively. Some people, after a stroke that damages the right cerebral hemisphere, seem unaware of any disability in their affected left limbs. This is called anosognosia or sensory inattention. There is no specific treatment for agnosia, but some interpretative ability may return eventually. agonist Having a stimulating effect. An agonist drug, sometimes known as an activator, is one that binds to a sensory nerve cell (receptor) and triggers or increases a particular activity in that cell. agoraphobia Fear of going into open spaces or public places. Agoraphobia (see phobia) may occur with claustrophobia. If sufferers do venture out, they may have a panic attack, which may lead to further restriction of activities. People with agoraphobia may eventually become housebound. Treatment with behaviour therapy is usually successful. Antidepressant drugs may be helpful. agraphia Loss of, or impaired, ability to write, despite normal functioning of the hand and arm muscles, caused by brain damage. Agraphia can result from damage to any of the various parts of the cerebrum concerned with writing and can therefore be of different types and degrees of severity. Such damage is most commonly due to head injury, stroke, or a brain tumour. Agraphia is often accompanied by alexia (loss of the ability to read) or may be part of an expressive aphasia (general disturbance in the expression of language). There is no specific treatment for agraphia, but some lost writing skills may return in time. ague An outdated term for malaria or other diseases causing fever in which particles). Aggregation is the 1st stage of blood clotting and helps to plug injured vessels. Inappropriate aggregation can have adverse effects; for example, if aggregation occurs in an artery, it may result in a thrombosis. aggression A general term for a wide variety of acts of hostility. A number of factors, including human evolutionary survival strategies, are thought to be involved in aggression. Androgen hormones, the male sex hormones, seem to promote aggression, whereas oestrogen hormones, the female sex hormones, actively suppress it. Age is another factor; aggression is more common among teenagers and young adults. Sometimes, a brain tumour or head injury leads to aggressive behaviour. Psychiatric conditions associated with aggressive outbursts are schizophrenia, antisocial personality disorder, mania, and abuse of amfetamines or alcohol. Temporal lobe epilepsy, hypoglycaemia, and confusion due to physical illnesses are other, less common, medical causes. aging The physical and mental changes that occur with the passing of time. Aging is associated with degenerative changes in various organs and tissues, such as loss of elasticity in the skin and a progressive decline in organ function. Mechanical wear and tear causes cumulative damage to the joints, and the muscles lose bulk and strength. Wound healing and resistance to infection also decline. Gradual loss of nerve cells can lead to reduced sensory acuity and difficulties with learning and memory. However, dementia occurs in only a minority of elderly people. Heredity is an important determinant of life expectancy, but physical degeneration may be accelerated by factors such as smoking, excessive alcohol intake, poor diet, and insufficient exercise. agitation Restless inability to keep still, usually as a result of anxiety or tension. Agitated people engage in aimless, repetitive behaviour, such as pacing up and down or wringing their hands, and they often start tasks without completing them. Persistent agitation is seen in anxiety disorders, especially if there is an underlying physical cause such as 16 AIDS AIR CONDITIONING candidiasis (thrush), shingles, tuberculosis, and shigellosis. HIV may also affect the sufferer alternately feels excessively hot and shiveringly cold. AIDS Acquired immune deficiency syndrome, a deficiency of the immune system due to infection with HIV (human immunodeficiency virus). In most countries, illness and death from AIDS is a growing health problem, and there is, as yet, no cure or vaccine. AIDS does not develop in all people infected with HIV. The interval between infection and the development of AIDS is highly variable. Without treatment, around half of those people infected will develop AIDS within 8–9 years. HIV is transmitted in body fluids, including semen, blood, vaginal secretions, and breast milk. The major methods of transmission are sexual contact (vaginal, anal, or oral), blood to blood (via transfusions or needle-sharing in drug users), and mother to fetus. HIV has also been transmitted through blood products given to treat haemophilia, artificial insemination by donated semen, and kidney transplants; but improved screening has greatly reduced these risks. HIV is not spread by everyday contact, such as hugging or sharing crockery. The virus enters the bloodstream and infects cells that have a particular receptor, known as the CD4 receptor, on their surface. These cells include a type of white blood cell (a CD4 lymphocyte) responsible for fighting infection and cells in other tissues such as the brain. The virus reproduces within the infected cells, which then die, releasing more virus particles into the blood. If the infection is left untreated, the number of CD4 lymphocytes falls, resulting in greater susceptibility to certain infections and some types of cancer. Some people experience a short-lived illness similar to infectious mononucleosis when they are first infected with HIV. Many individuals have no obvious symptoms; some have only vague complaints, such as weight loss, fevers, sweats, or unexplained diarrhoea, described as AIDS-related complex. Minor features of HIV infection include skin disorders such as seborrhoeic dermatitis. More severe features include persistent herpes simplex infections, oral the brain, causing a variety of neurological disorders, including dementia. Certain conditions, known as AIDSdefining illnesses, are characteristic of full-blown AIDS. These include cancers (Kaposi’s sarcoma and lymphoma of the brain), and various infections (pneumocystis pneumonia, cytomegalovirus infection, toxoplasmosis, diarrhoea due to CRYPTOSPORIDIUM or ISOSPORA, candidiasis, disseminated strongyloidiasis, and cryptococcosis), many of which are described as opportunistic infections. Confirmation of HIV infection involves testing a blood sample for the presence of antibodies to HIV. Diagnosis of fullblown AIDS is based on a positive HIV test along with the presence of an AIDSdefining illness. The risk of infection with HIV can be reduced by practising safer sex. Intravenous drug users should not share needles. There is a small risk to health workers handling infected blood products or needles, but this risk can be minimized by safe practices. Treatment of HIV infection with a combination of antiviral drugs can slow the disease’s progress, and may prevent the development of full-blown AIDS. The 2 main types of antiviral drug used are protease inhibitors, such as indinavir, and reverse transcriptase inhibitors such as zidovudine. Treatment is also available for AIDS-defining illnesses. AIDS-related complex A combination of weight loss, fever, and enlarged lymph nodes in a person who has been infected with HIV (the AIDS virus), but does not have AIDS itself. Many people with AIDS-related complex will eventually develop the features of AIDS. air The colourless, odourless mixture of gases that forms the Earth’s atmosphere. Air consists of 78 per cent nitrogen, 21 per cent oxygen, small quantities of carbon dioxide and other gases, and some water vapour. air conditioning A system that controls the purity, humidity, and temperature of the air in a building. Contaminated air-conditioning systems may cause legionnaires’ disease and humidifier fever 17 A A AIR EMBOLISM ALCOHOL (a lung disease causing coughing and breathing difficulty). air embolism Blockage of a small artery by an air bubble carried in the blood. Air embolism is rare. In most cases, it is caused by air entering the circulation through a vein, either due to injury or surgery. Air embolism can also occur during diving or air travel accidents, in which lung tissue ruptures, releasing bubbles into the bloodstream. air pollution See pollution. air swallowing See aerophagy. airway A collective term for the passages through which air enters and leaves the lungs (see respiratory system). The term is also applied to a tube inserted into the mouth of an unconscious person to prevent the tongue from obstructing breathing. airway obstruction Narrowing or blockage of the respiratory passages. The obstruction may be due to a foreign body, such as a piece of food, that becomes lodged in part of the upper airway and may result in choking. Certain disorders, such as diphtheria and lung cancer, can cause obstruction. Additionally, spasm of the muscular walls of the airway, as occurs in bronchospasm (a feature of asthma), results in breathing difficulty. akathisia An inability to sit still, occasionally occurring as a side effect of an antipsychotic drug or, less commonly, as a complication of Parkinson’s disease. akinesia Complete or almost complete loss of movement. It may be a result of damage to part of the brain due, for example, to a stroke or Parkinson’s disease. albinism A rare genetic disorder characterized by a lack of the pigment melanin, which gives colour to the skin, hair, and eyes. In oculocutaneous albinism (the most common type), the hair, skin, and eyes are all affected. Less often, only the eyes are affected. In both forms, skin cannot tan and ages prematurely, and skin cancers may develop on areas exposed to the sun. Visual problems of people with albinism include photophobia, nystagmus, squint, and myopia. Glasses are usually needed from an early age; and tinted glasses help to reduce photophobia. albumin The most abundant protein in the blood plasma. Albumin is made in the liver from amino acids. It helps to retain substances (such as calcium, some hormones, and certain drugs) in the circulation by binding to them to prevent them from being filtered out by the kidneys and excreted. Albumin also regulates the movement of water between tissues and the bloodstream by osmosis. (See also albuminuria.) albuminuria The presence of the protein albumin in the urine; a type of proteinuria. Normally, the glomeruli (the filtering units of the kidneys) do not allow albumin to pass into the urine. Albuminuria therefore usually indicates that there is damage to the kidneys’ filtering mechanisms. Such damage may be due to a kidney disorder, such as glomerulonephritis or nephrotic syndrome, or may be a sign that the kidneys have been affected by hypertension. Albuminuria can be detected by a simple urine test. alcohol A colourless liquid produced from the fermentation of carbohydrates by yeast. Also known as ethanol, alcohol is the active constituent of drinks such as beer and wine. In medicine, it is used as an antiseptic and solvent. Methanol is a related, highly toxic substance. Alcohol is a drug and produces a wide range of mental and physical effects. The effect of alcohol on the central nervous system is as a depressant, decreasing its activity and thereby reducing anxiety, tension, and inhibitions. In moderate amounts, alcohol produces a feeling of relaxation, confidence, and sociability. However, alcohol slows reactions, and the more that is drunk, the greater is the impairment of concentration and judgement. Excessive consumption of alcohol results in poisoning or acute alcohol intoxication, with effects ranging from euphoria to unconsciousness. Short-term physical effects of alcohol include peripheral vasodilation (widening of the small blood vessels), which causes the face to flush, and increased flow of gastric juices, which stimulates the appetite. Alcohol increases sexual confidence, but high levels can cause 18 ALCOHOL DEPENDENCE ALCOHOL INTOXICATION tingling; weakness in the legs and hands; irregular pulse; enlarged blood vessels in the face; unsteadiness; confusion; memory lapses; and incontinence. After sudden withdrawal from alcohol, delirium tremens may occur. Alcohol-dependent persons are more susceptible than others to a variety of physical and mental disorders (see alcohol-related disorders). Many alcoholics require detoxification followed by long-term treatment. Different methods of treatment may be combined. Psychological treatments involve psychotherapy and are commonly carried out as group therapy. Social treatments may offer practical help and tend to include family members in the process. Physical treatment generally includes the use of disulfiram, a drug that sensitizes the drinker to alcohol so that he or she experiences unpleasant side effects when drinking. Alcoholics Anonymous and other self-help organizations can provide support and advice. Alcoholics Anonymous A worldwide, independent, self-help organization that is operated locally by people working on a voluntary basis to overcome alcohol dependence. Regular group meetings are held in which members are encouraged to help one another stay sober by sharing their experiences openly and offering support and advice. alcohol intoxication The condition that results from consuming an excessive amount of alcohol, often over a relatively short period. The effects of a large alcohol intake depend on many factors, including physical and mental state, body size, social situation, and acquired tolerance. The important factor, however, is the blood alcohol level. Mild intoxication promotes relaxation and increases social confidence. Alcohol causes acute poisoning if taken in sufficiently large amounts, however. It depresses the activity of the central nervous system, leading to loss of normal mental and physical control. In extreme cases, intoxication may lead to loss of consciousness and even death. In most cases, recovery from alcohol intoxication takes place naturally as the alcohol is gradually broken down in impotence. Alcohol also acts as a diuretic, increasing urine output. In the long term, regular excessive alcohol consumption can cause gastritis (inflammation and ulceration of the stomach lining), and lead to alcoholrelated disorders. Heavy drinking in the long term may also lead to alcohol dependence. However, people who drink regular, small amounts of alcohol (an average of 1–2 units a day) seem to have lower rates of coronary heart disease and stroke than total abstainers. alcohol dependence An illness characterized by habitual, compulsive, longterm, heavy consumption of alcohol and the development of withdrawal symptoms when drinking is suddenly stopped. Three causative factors interact in the development of the illness: personality, environment, and the addictive nature of alcohol. Inadequate, insecure, or immature personalities are more at risk. Environmental factors are important, especially the ready availability, affordability, and social acceptance of alcohol. Genetic factors may play a part in causing dependence in some cases, but it is now widely believed that anyone, irrespective of personality, environment, or genetic background, can become an alcoholic. Stress is often a major factor in precipitating heavy drinking. Alcohol dependence usually develops in 4 main stages that occur over a number of years. In the 1st phase, tolerance to alcohol develops in the heavy social drinker. In the 2nd phase, the drinker experiences memory lapses relating to events during the drinking episodes. In the 3rd phase, there is loss of control over alcohol consumption. The final phase is characterized by prolonged binges of intoxication and mental or physical complications. Behavioural symptoms are varied and can include furtive, aggressive, or grandiose behaviour; personality changes (such as irritability, jealousy, or uncontrolled anger); neglect of food intake and personal appearance; and lengthy periods of intoxication. Physical symptoms may include nausea, vomiting, or shaking in the morning; abdominal pain; cramps; numbness or 19 A A ALCOHOLISM ALEXIA the liver. Medical attention is required if the intoxication has resulted in coma. For the chronic mental, physical, and social effects of long-term heavy drinking, see alcohol dependence and alcohol-related disorders. alcoholism See alcohol dependence. alcohol-related disorders A wide variety of physical and mental disorders associated with heavy, prolonged consumption of alcohol. High alcohol consumption increases the risk of cancers of the mouth, tongue, pharynx (throat), larynx (voice box), and oesophagus, especially if combined with smoking. Incidence of liver cancer, as well as the liver diseases alcoholic hepatitis and cirrhosis, is higher among alcoholics. High alcohol consumption increases the risk of cardiomyopathy, hypertension, and stroke. Alcohol irritates the digestive tract and may cause gastritis. Heavy drinking in pregnancy increases the risk of miscarriage and fetal alcohol syndrome. Alcoholics are more likely to suffer from anxiety and depression and to develop dementia. Many alcoholics have a poor diet and are prone to diseases caused by nutritional deficiency, particularly of thiamine (see vitamin B complex). Severe thiamine deficiency, called beriberi, disturbs nerve function, causing cramps, numbness, and weakness in the legs and hands. Its effects on the brain can cause confusion, disturbances of speech and gait, and eventual coma (see Wernicke– Korsakoff syndrome). Severe thiamine deficiency can also cause heart failure. A prolonged high level of alcohol in the blood and tissues can disturb body chemistry, resulting in hypoglycaemia (reduced glucose in the blood) and hyperlipidaemia (increased fat in the blood). These may damage the heart, liver, blood vessels, and brain; irreversible damage may cause premature death. aldosterone A hormone secreted by the adrenal cortex (the outer part of the adrenal glands). Aldosterone acts on the kidneys to regulate the concentrations of sodium and potassium in the blood and tissues and control blood pressure. Production of aldosterone is stimulated mainly by the action of angiotensin II, a chemical produced by a series of reactions involving the enzymes renin and angiotensin-converting enzyme. Aldosterone production is also stimulated by the action of ACTH, which is produced by the pituitary gland. aldosteronism A disorder that results from the excessive production of the hormone aldosterone from one or both adrenal glands. Aldosteronism caused by an adrenal tumour is known as Conn’s syndrome. Aldosteronism may also be caused by disorders, such as heart failure or liver damage, that reduce the flow of blood through the kidneys. Reduced blood flow through the kidneys leads to overproduction of renin and angiotensin, which, in turn, leads to excessive aldosterone production. Symptoms are directly related to the actions of aldosterone. Too much sodium is retained in the body, leading to a rise in blood pressure, and excess potassium is lost in the urine. Low potassium causes tiredness and muscle weakness and impairs kidney function, leading to thirst and overproduction of urine. Treatment in all cases includes restriction of dietary salt and use of the diuretic drug spironolactone. If the cause of aldosteronism is an adrenal tumour, this may be surgically removed. alendronate sodium See alendronic acid. alendronic acid A bisphosphonate drug used in the treatment of osteoporosis and Paget’s disease of bone. The most common side effect is inflammation of the oesophagus, which causes heartburn or difficulty in swallowing. Other side effects can include headache and abdominal pain. Alexander technique A therapy that aims to improve health by teaching people to stand and move more efficiently. The technique is based on the belief that bad patterns of body movement interfere with the proper functioning of the body and contribute to the development of disease. alexia Word blindness; inability to recognize and name written words. Alexia is caused by damage to part of the cerebrum (the main mass of the brain) by a stroke, for example. It severely disrupts 20 ALIENATION ALLERGY the reading ability of a person who was previously literate. (See also dyslexia.) alienation Feeling like a stranger, even when among familiar people or places, and being unable to identify with a culture, family, or peer group. Alienation is common in adolescents and also occurs in people who are isolated by cultural or language differences. In some people, it may be an early symptom of schizophrenia or a personality disorder. alignment, dental The movement of teeth by using either fixed or removable orthodontic appliances (braces) to correct malocclusion (incorrect bite). alimemazine An antihistamine drug, also known as trimeprazine, that is used mainly to relieve itching in allergic conditions such as urticaria and atopic eczema. Alimemazine often causes drowsiness. alimentary tract The tube-like structure that extends from the mouth to the anus (see digestive system). alkali Also known as a base, an alkali is chemically defined as a donor of hydroxyl ions (each of which comprises an atom of hydrogen linked to an atom of oxygen and has an overall negative electrical charge). Antacid drugs, such as sodium bicarbonate, are alkalis. Some alkalis, such as sodium hydroxide, are corrosive. (See also acid; acid–base balance.) alkaloids A group of nitrogen-containing substances obtained from plants. Morphine, codeine, nicotine, and strychnine (see strychnine poisoning) are examples. alkalosis A disturbance of the body’s acid–base balance in which there is an accumulation of alkali or a loss of acid. There are 2 types: metabolic and respiratory. In metabolic alkalosis, the increase in alkalinity may be caused by taking too much of an antacid drug or by losing a large amount of stomach acid as a result of severe vomiting. In respiratory alkalosis, there is a reduction in the blood level of carbonic acid (derived from carbon dioxide). This reduction is a consequence of hyperventilation, which may occur during a panic attack or at high altitudes due to lack of oxygen. (See also acidosis.) alkylating agents A class of anticancer drugs. allele One of 2 or more different forms of a gene that occupies a specific position on a chromosome (see gene; inheritance). allergen A normally harmless substance that causes an allergic reaction (see allergy) in people who have become sensitized to it. Allergens can include foods (for example, nuts, eggs, and shellfish); inhaled substances such as pollen, house dust, and fur; and some drugs. allergy Various conditions caused by inappropriate or exaggerated reactions of the immune system (known as hypersensitivity reactions) to a variety of substances. Many common illnesses, such as asthma and allergic rhinitis (hay fever), are caused by allergic reactions to substances that in the majority of people cause no symptoms. Allergic reactions occur only on 2nd or subsequent exposure to the allergen, once 1st contact has sensitized the body. The function of the immune system is to recognize antigens (foreign proteins) on the surfaces of microorganisms and to form antibodies (also called immunoglobulins) and sensitized lymphocytes (white blood cells). When the immune system next encounters the same antigens, the antibodies and sensitized lymphocytes interact with them, leading to destruction of the microorganisms. A similar immune response occurs in allergies, except that the immune system forms antibodies or sensitized lymphocytes against harmless substances because these allergens are misidentified as potentially harmful antigens. The inappropriate or exaggerated reactions seen in allergies are termed A ALLERGY Allergen Mast cell Antibody attaches to mast cell Histamine Allergen binds to antibody Histamine released Nucleus TYPE I HYPERSENSITIVITY 21 A ALLOPATHY ALOPECIA hypersensitivity reactions and can have reactions to specific allergens such as bee stings. Treatment involves gradually increasing doses of the allergen, but it must be carried out under close supervision because a severe allergic reaction can result. allopathy The practice of conventional medicine. (See also homeopathy.) allopurinol A drug treatment for gout. Taken long term, it reduces the frequency of attacks by decreasing production of uric acid. Possible adverse reactions include itching, rashes, and nausea. alopecia Loss or absence of hair, which may occur at any hair-bearing site on the body but which is usually noticeable only on the scalp. Male-pattern baldness, the most common form of alopecia, is hereditary and most often affects men. Normal hair is lost initially from the temples and crown and is replaced by fine, downy hair; the affected area gradually widens. Other hereditary forms are rare. They may be due to an absence of hair roots or abnormalities of the hair shaft. In generalized alopecia, the hair falls out in large amounts. Causes include various forms of stress, such as surgery, prolonged illness, or childbirth. Many anticancer drugs cause temporary alopecia. The hair regrows when the underlying cause is corrected. Localized alopecia may be due to permanent skin damage (for example, by burns or radiotherapy) or trauma to the hair roots by styling or, rarely, trichotillomania (a disorder in which sufferers pull out their hair). The most common type of localized hair loss is alopecia areata, which is an autoimmune disorder. There is no specific treatment, but the hair usually regrows within a few months. Alopecia universalis is a rare, permanent form of alopecia areata that causes loss of all the hair on the scalp and body, including the eyelashes and eyebrows. Skin diseases such as scalp ringworm (see tinea), lichen planus, lupus erythematosus, and skin tumours may also cause localized hair loss. Treatments for male-pattern baldness include hair transplants or drug treatments with minoxidil or finasteride. any of four different mechanisms (termed Types I to IV hypersensitivity reactions). Most well known allergies are caused by Type I (also known as anaphylactic or immediate) hypersensitivity in which allergens cause immediate symptoms by provoking the immune system to produce specific antibodies, belonging to a type called immunoglobulin E (IgE), which coat cells (called mast cells or basophils). When the allergen is encountered for the second time, it binds to the IgE antibodies and causes the granules in mast cells to release various chemicals, which are responsible for the symptoms of the allergy. Among the chemicals released is histamine, which causes widened blood vessels, leakage of fluid into tissues, and muscle spasm. Symptoms can include itching, swelling, sneezing, and wheezing. Particular conditions associated with Type I reactions include asthma, hay fever, urticaria (nettle rash), angioedema, anaphylactic shock (a severe, generalized allergic reaction), possibly atopic eczema, and many food allergies. Types II to IV hypersensitivity reactions are less often implicated in allergies. However, contact dermatitis, in which the skin reacts to substances such as nickel, is due to a Type IV hypersensitivity reaction. It is not known why certain individuals and not others get allergies, but about 1 in 8 people seem to have an inherited predisposition to them (see atopy). Whenever possible, the most effective treatment for allergy of any kind is avoidance of the relevant allergen. Drug treatment for allergic reactions includes the use of antihistamine drugs, which relieve the symptoms. Some antihistamine drugs have a sedative effect, which is useful in treating itching at night due to eczema. Many antihistamines do not cause drowsiness, making them more suitable for daytime use. Other drugs, such as sodium cromoglicate and corticosteroid drugs, can be used regularly to prevent symptoms from developing. Hyposensitization can be valuable for a minority of people who suffer allergic 22 ALPHA 1 -ANTITRYPSIN DEFICIENCY ALVEOLITIS alpha1-antitrypsin deficiency A rare genetic disorder in which a person is missing the enzyme alpha1-antitrypsin, which protects the body from damage by other enzymes. The disease mainly affects tissues in the lungs, resulting in emphysema, and the liver, causing cirrhosis. The effects of alpha1-antitrypsin deficiency may not become apparent until after the age of 30. There is no cure, but symptoms can be relieved by drug treatment. In severe cases, a liver transplant may be a possibility. alpha-blocker drugs A group of drugs used to treat hypertension (high blood pressure) and urinary symptoms due to enlargement of the prostate gland. Alpha-blockers are also used to treat urinary retention caused by an enlarged prostate gland (see prostate, enlarged). Side effects of the drugs may include dizziness and fatigue due to a sudden drop in blood pressure, nausea, dry mouth, and drowsiness. alpha-fetoprotein A protein that is produced in the liver and gastrointestinal tract of the fetus and by some abnormal tissues in adults. Alpha-fetoprotein (AFP) can be measured in the maternal blood from the latter part of the 1st trimester of pregnancy, and its concentration rises between the 15th and 20th weeks. Raised levels of AFP are associated with fetal neural tube defects, such as spina bifida or anencephaly, and certain kidney abnormalities. High levels of AFP also occur in multiple pregnancies (see pregnancy, multiple) and threatened or actual miscarriage. AFP levels may be unusually low if the fetus has Down’s syndrome. For this reason, measurement of blood AFP is included in blood tests, which are used to screen pregnant women for an increased risk of Down’s syndrome. AFP levels are commonly raised in adults with hepatoma (see liver cancer), cancerous teratoma of the testes or ovaries, or cancer of the pancreas, stomach, or lung. For this reason, AFP is known as a tumour marker. AFP levels can be used to monitor the results of treatment of certain cancers; increasing levels after surgery or chemotherapy may indicate tumour recurrence. However, AFP levels are also raised in some noncancerous conditions, including viral and alcoholic hepatitis and cirrhosis. alprazolam A benzodiazepine drug used in the treatment of anxiety, panic attacks, and phobias. alprostadil A prostaglandin drug used, prior to surgery, to minimize the effects of congenital heart defects in newborn babies. Alprostadil is also used as a treatment for impotence. It is administered by self-injection into the penis or as a gel introduced into the urethra to produce an erection. alternative medicine Any medical system based on a theory of disease or method of treatment other than the orthodox science of Western medicine. (See also complementary medicine.) altitude sickness See mountain sickness. aluminium A light, metallic element found in bauxite and various other minerals. Aluminium compounds are used in antacid medications and in antiperspirants. Most of the aluminium taken into the body is excreted. Excessive amounts are toxic and are stored in the lungs, brain, liver, and thyroid gland, where they may result in organ damage. Certain industrial processes give off fumes containing aluminium into the air. These fumes can cause fibrosis of lung tissue. Drugs that contain aluminium may interfere with the absorption of other drugs and, therefore, should not be taken at the same time. alveolectomy See alveoloplasty. alveolitis Inflammation and thickening of the walls of the alveoli (tiny air sacs) in the lungs. Alveolitis reduces the elasticity, and therefore the efficiency, of the lungs. It is most commonly due to an allergic reaction to inhaled dust of animal or plant origin, as in farmer’s lung, bagassosis, and pigeon fancier’s lung (due to particles from bird droppings). Fibrosing alveolitis is an autoimmune disorder. In some cases, it occurs with other autoimmune disorders such as rheumatoid arthritis or systemic lupus erythematosus. Radiation alveolitis is caused by irradiation of the lungs and may occur as a rare complication of radiotherapy for lung or breast cancer. 23 A A ALVEOLOPLASTY AMAUROSIS FUGAX Alveolitis usually causes a dry cough and breathing difficulty on exertion. A chest X-ray, blood tests, pulmonary function tests, or a lung biopsy may be needed to diagnose alveolitis. For most types of alveolitis, a short course of corticosteroid drugs relieves symptoms, but for fibrosing alveolitis these may need to be taken indefinitely. If the cause of allergic alveolitis is recognized and avoided before lung damage occurs, the effects are not permanent. In fibrosing alveolitis, damage progresses despite treatment, causing increasing breathing difficulty and, sometimes, respiratory failure. alveoloplasty Dental surgery to remove protuberances and smooth out uneven areas from tooth-bearing bone in the jaw before the fitting of dentures. alveolus, dental The bony cavity or socket supporting each tooth in the jaw. alveolus, pulmonary One of a large number of tiny, balloon-like sacs at the end of a bronchiole (one of many small air passages in the lungs) where gases are exchanged during respiration. are responsible for the production of the blood protein apolipoprotein E. These genes also result in the deposition of a protein called beta amyloid in the brain. Other chemical abnormalities may include deficiency of the neurotransmitter acetylcholine. The features of Alzheimer’s disease vary, but there are 3 broad stages. At first, the person becomes increasingly forgetful, and problems with memory may cause anxiety and depression. In the 2nd stage, loss of memory, particularly for recent events, gradually becomes more severe, and there may be disorientation as to time or place. The person’s concentration and numerical ability decline, and there is noticeable dysphasia (inability to find the right word). Anxiety increases, mood changes are unpredictable, and personality changes may occur. Finally, confusion becomes profound. There may be symptoms of psychosis, such as hallucinations and delusions. Signs of nervous system disease, such as abnormal reflexes and faecal or urinary incontinence, begin to develop. Alzheimer’s disease is usually diagnosed from the symptoms, but tests including blood tests and CT scanning or MRI of the brain may be needed to exclude treatable causes of dementia. The most important aspect of treatment for Alzheimer’s disease is the provision of suitable nursing and social care for sufferers and support for their relatives. Tranquillizer drugs can often improve difficult behaviour and help with sleep. Treatment with drugs such as donepezil and rivastigmine may slow the progress of the disease for a time, but side effects such as nausea and dizziness may occur. amalgam, dental A material, consisting of an alloy of mercury with other metals, that is used as fillings for teeth (see filling, dental). amantadine An antiviral drug used in the prevention and treatment of influenza A and to help relieve symptoms of Parkinson’s disease. amaurosis fugax Brief loss of vision, lasting for seconds or minutes, usually affecting one eye only and caused by ALVEOLUS, PULMONARY Trachea Thin wall of alveolus Air space Pleura Blood vessel ALVEOLI Bronchus LUNGS Bronchiole Alzheimer’s disease A progressive condition in which nerve cells in the brain degenerate and the brain shrinks. Alzheimer’s disease is the most common cause of dementia. Onset is uncommon before the age of 60. Early onset Alzheimer's disease, in which symptoms develop before age 60, is inherited as a dominant disorder. Late onset Alzheimer's disease is associated with a number of genes, including 3 that 24 AMBIDEXTERITY AMFETAMINE DRUGS the temporary blockage of a small blood vessel in the eye by emboli (particles of solid matter such as cholesterol or clotted blood). These are carried in the bloodstream from diseased arteries in the neck or, rarely, the heart. Attacks may be infrequent or they may occur many times a day. This symptom indicates an increased risk of stroke and requires medical investigation. ambidexterity The ability to perform manual skills equally well with either hand because there is no definite handedness. Ambidexterity is an uncommon and often familial trait. amblyopia A permanent defect of visual acuity in which there is usually no structural abnormality in the eye. In many cases, there is a disturbance of the visual pathway between the retina and the brain. The term is also sometimes applied to toxic or nutritional causes of decreased visual acuity, as in tobacco–alcohol amblyopia. Amblyopia will develop if there is a marked discrepancy between the images received by the brain from each eye while vision is developing during early childhood. The most common cause is squint. Failure to form normal retinal images may also result from congenital cataract, and severe, or unequal, focusing errors, such as when one eye is normal and there is an uncorrected large degree of astigmatism in the other. Toxic and nutritional amblyopia may result from damage to the retina and/or the optic nerve. To prevent amblyopia due to squint, patching (covering up the good eye to force the deviating eye to function properly) is the usual treatment. Surgery to place the deviating eye in the correct position may be necessary. Glasses may be needed to correct severe focusing errors. Cataracts may be removed surgically. After the age of 8, amblyopia cannot usually be remedied. ambulance A vehicle for transporting sick or injured people that is staffed by trained personnel who can provide emergency treatment during the journey. ambulatory ECG In ambulatory ECG (electrocardiography), a wearable device called a Holter monitor is used to record the electrical activity of the heart by means of electrodes attached to the chest. The monitor is usually worn for 24 hours or longer and detects intermittent arrhythmias (abnormal heart rates and rhythms). The wearer can press a button on the monitor to mark the recording whenever symptoms occur. The recording can later be analysed to see if the periods of arrhythmia coincide with the symptoms. amelogenesis imperfecta An inherited condition of the teeth in which the enamel is either abnormally thin or is deficient in calcium. Affected teeth may be pitted and discoloured (see discoloured teeth) and more susceptible to dental caries (tooth decay) and wear. amenorrhoea The absence of menstrual periods. Primary amenorrhoea is defined as failure to start menstruating by the age of 16. Secondary amenorrhoea is the temporary or permanent cessation of periods in a woman who has menstruated regularly in the past. The main cause of primary amenorrhoea is delayed puberty. The delay may not indicate a disorder, but, rarely, it may result from a disorder of the endocrine system, such as a pituitary tumour, hypothyroidism, an adrenal tumour, or adrenal hyperplasia. Another rare cause of delayed puberty is Turner’s syndrome. In some cases, menstruation fails to take place because the vagina or the uterus has been absent from birth, or because there is no perforation in the hymen to allow blood to escape. The most common cause of temporary secondary amenorrhoea is pregnancy. Periods may also cease temporarily after a woman has stopped taking oral contraceptives. Secondary amenorrhoea may also result from hormonal changes due to stress, depression, anorexia nervosa, or certain drugs. Another possible cause is a disorder of the ovary such as polycystic ovary (see ovary, polycystic) or an ovarian tumour. Amenorrhoea occurs permanently following the menopause or after a hysterectomy. amfetamine drugs A group of stimulant drugs used mainly in the treatment of narcolepsy (a rare disorder characterized by excessive sleepiness). 25 A A AMILORIDE AMNIOCENTESIS amiodarone An antiarrhythmic drug used in the treatment of various types of arrhythmia (irregular heartbeat). Longterm use of amiodarone may result in inflammation of the liver, thyroid problems, and eye and lung damage. amitriptyline A tricyclic antidepressant drug with a sedative effect. It is useful in the treatment of depression accompanied by anxiety or insomnia. Possible adverse effects include blurred vision, dizziness, and drowsiness. amlodipine A calcium channel blocker drug used to prevent angina and to treat hypertension. Possible side effects are headaches and dizziness. ammonia A colourless, pungent gas that dissolves in water to form ammonium hydroxide, an alkaline solution (see alkali). Ammonia is produced in the body and helps to maintain the acid–base balance. In severe liver damage, the ability of the liver to convert ammonia to urea is reduced. This leads to a high level of ammonia in the blood, which is thought to be a cause of the impaired consciousness that occurs in liver failure. amnesia Loss of ability to memorize information and/or to recall information stored in memory. Possible causes of amnesia are head injury; degenerative disorders such as Alzheimer’s disease and other forms of dementia; infections such as encephalitis; thiamine deficiency in alcoholics, leading to Wernicke– Korsakoff syndrome; brain tumours; strokes; and subarachnoid haemorrhage. Amnesia can also occur in some forms of psychiatric illness. In retrograde amnesia, the loss of memory extends back for some time before the onset of the disorder. In anterograde amnesia, there is an inability to store new information in the period following the onset of illness. amniocentesis A diagnostic procedure in which a small amount of amniotic fluid is withdrawn, using a syringe and guided by ultrasound scanning, from the amniotic sac that surrounds the fetus in the uterus. This fluid contains fetal cells that can be subjected to chromosome analysis to identify chromosomal defects such as Down’s syndrome or genetic analysis to look for genetic In high doses, amfetamines can cause tremor, sweating, anxiety, and sleeping problems. Delusions, hallucinations, high blood pressure, and seizures may also occur. Prolonged use may produce tolerance and drug dependence. Amfetamines are often abused for their stimulant effect. amiloride A potassium-sparing diuretic drug. Combined with loop or thiazide diuretics, amiloride is used to treat hypertension and fluid retention due to heart failure or cirrhosis of the liver. amino acids A group of chemical compounds that form the basic structural units of all proteins. Each amino acid molecule consists of amino and carboxyl groups of atoms linked to a variable chain or ring of carbon atoms. Individual amino acid molecules are linked together by chemical bonds called peptide bonds to form short chains of molecules called polypeptides. Hundreds of polypeptides are, in turn, linked together, also by peptide bonds, to form a protein molecule. What differentiates one protein from another is the sequence of the amino acids. There are 20 different amino acids that make up all the proteins in the body. Of these, 12 can be made by the body; they are known as nonessential amino acids because they do not need to be obtained from the diet. The other 8, known as the essential amino acids, cannot be made by the body and must therefore be obtained from the diet. aminoglutethimide An anticancer drug used to treat certain types of breast cancer, prostate cancer, and some endocrine gland tumours. aminoglycoside drugs A type of antibiotic drug. Aminoglycoside drugs are given by injection and are generally reserved for the treatment of serious infections because their use can damage the inner ear or kidneys. Important examples are gentamicin and streptomycin, which are also used topically for eye and ear infections. aminophylline A bronchodilator drug used to treat chronic bronchitis, asthma, and, occasionally, heart failure. Nausea, vomiting, headache, dizziness, and palpitations are possible side effects. 26 AMNION AMOXICILLIN Occasionally, excessive fluid is formed (see polyhydramnios); less frequently, insufficient amniotic fluid is formed (see oligohydramnios). amniotic sac The membranous bag that surrounds the fetus and is filled with amniotic fluid as pregnancy advances. The sac is made up of 2 membranes, the inner amnion and the outer chorion. amniotomy Artificial rupture of the amniotic membranes (breaking the “waters”) performed for induction of labour. amoeba A type of protozoon (see protozoa). An amoeba is a microscopic single-celled organism with an irregular, changeable shape. Amoebae live in moist environments, such as fresh water and soil. Some types of amoebae are parasites of humans, causing diseases such as amoebiasis. amoebiasis An infection caused by the amoeba ENTAMOEBA HISTOLYTICA, a tiny single-celled parasite that lives in the human large intestine. Amoebiasis is spread through drinking water or eating food contaminated by human excreta containing cysts of the amoeba. Some people carry the amoeba in their intestines and excrete cysts but have no symptoms. However, some strains invade and ulcerate the intestinal wall, causing diarrhoea and abdominal pain, which may develop into full-blown dysentery. The amoebae may spread via the bloodstream to the liver, or, rarely, the brain or lung, where they cause abscesses. Symptoms of an amoebic liver abscess are chills, fever, weight loss, and painful enlargement of the liver. Treatment of all forms of amoebiasis is with drugs such as metronidazole or diloxanide, which kill the parasite within a few weeks, leading to full recovery. amoebic dysentery See amoebiasis. amoebicides A group of drugs used to treat amoebiasis. Examples are diloxanide, and metronidazole. amoxapine An antidepressant drug related to the tricyclics. Possible adverse effects include blurred vision, dizziness, drowsiness, abnormal muscular movements, menstrual irregularities, and breast enlargement. amoxicillin A penicillin drug commonly used to treat a variety of infections, AMNIOCENTESIS Syringe Ultrasound probe Amniotic fluid Ultrasound beam Bladder Fetus Cervix Uterus Placenta disorders such as haemophilia, cystic fibrosis, and Tay–Sachs disease. Chemi- cal analysis of amniotic fluid can help to diagnose developmental abnormalities such as spina bifida. Rhesus incompatibility and maturity of the fetal lungs can also be checked. Amniocentesis is usually performed in the 14th–18th week of pregnancy. It slightly increases the risk of miscarriage or early rupture of the membranes and is therefore recommended only when the fetus is thought to be at increased risk of an abnormality. (See also antenatal care, chorionic villus sampling.) amnion One of the membranes that surrounds the fetus in the uterus. The outside of the amnion is covered by another membrane called the chorion. amniotic fluid The clear, watery fluid (popularly called the “waters”) that surrounds the fetus in the uterus. The fluid is contained within the amniotic sac. It cushions the fetus, allowing movement. Amniotic fluid is produced by cells lining the amniotic sac and is constantly circulated. It appears in the 1st week after conception and gradually increases in volume until the 10th week, when the increase becomes very rapid. 27 A A AMOXYCILLIN AMYLOIDOSIS including bronchitis, cystitis, and ear and skin infections. Allergy to amoxicillin causes a blotchy rash and, rarely, fever, swelling of the mouth and tongue, itching, and breathing difficulty. amoxycillin See amoxicillin. amphetamine drugs See amfetamine drugs. amphotericin B A drug used to treat fungal infections. Lozenges are used for candidiasis of the mouth. Life-threatening infections, such as cryptococcosis and histoplasmosis, are treated by injection. Adverse effects may occur with injection and include vomiting, fever, headache, and, rarely, seizures. ampicillin A penicillin drug commonly used to treat cystitis, bronchitis, and ear infections. Diarrhoea is a common adverse effect of ampicillin. Some people are allergic to it and suffer from rash, fever, swelling of the mouth and tongue, itching, and breathing difficulty. ampulla An enlarged, flask-shaped area at the end of a tubular structure or canal. There are several ampullae in the body, including at the end of the fallopian tubes, at the opening of the bile duct into the intestine, and on each of the semicircular canals of the inner ear. development of gangrene. Amputation may also be needed if a limb has been irreparably damaged in an accident. For some time after amputation, there may be an unpleasant sensation that the limb is still present, a phenomenon known as “phantom limb”. A prosthesis (see limb, artificial) is usually fitted when the stump has healed. amputation, congenital The separation of a body part (usually a limb, finger, or toe) from the rest of the body, as a result of the part’s blood supply being blocked by a band of amnion (fetal membrane) in the uterus. The affected part may be completely separated or show the marks of the “amniotic band” after birth. (See also limb defects.) amputation, traumatic Loss of a finger, toe, or limb through injury. (See also microsurgery.) amylase An enzyme found in saliva and pancreatic secretions (see pancreas). It helps to digest dietary starch, breaking it down into smaller components such as the sugars glucose and maltose. amyl nitrite A nitrate drug formerly prescribed to relieve angina. Because amyl nitrite frequently causes adverse effects, it has been superseded by other drugs. It is sometimes abused for its effect of intensifying pleasure during orgasm. amyloidosis An uncommon disease in which a substance called amyloid, composed of fibrous protein, accumulates in tissues and organs, including the liver, kidneys, tongue, spleen, and heart. Amyloidosis may occur for no known reason, in which case it is called primary; more commonly, it is a complication of some other disease, and in such cases it is called secondary. Conditions that may lead to amyloidosis include multiple myeloma (a cancer of bone marrow), rheumatoid arthritis, tuberculosis, and some other longstanding infections, such as chronic osteomyelitis. The symptoms of amyloidosis vary, depending on the organs affected and the duration of the condition. Deposits of amyloid in the kidneys may cause kidney failure, which may be fatal. There is no treatment, but secondary amyloidosis can be halted if the underlying disorder is treated. AMPULLA Semicircular canal Cochlea Ampulla Outer Middle Inner ear ear ear INNER EAR Cochlea LOCATION amputation Surgical removal of part or all of a limb. Amputation is necessary if peripheral vascular disease as a result of atherosclerosis or diabetes mellitus has impaired the blood supply to a limb. If blood supply cannot be restored, amputation is carried out to prevent the 28 AMYOTROPHIC LATERAL SCLEROSIS ANAEMIA, HAEMOLYTIC amyotrophic lateral sclerosis See motor neuron disease. amyotrophy Shrinkage or wasting away of a muscle, leading to weakness. Amyotrophy is usually due to poor nutrition, reduced use of the muscle (as when a limb is immobilized for a long period), or disruption of the blood or nerve supply to the muscle (as can occur in diabetes mellitus or poliomyelitis). anabolic steroids See steroids, anabolic. anabolism The manufacture of complex molecules, such as fats and proteins, from simpler molecules by metabolic processes in living cells. (See also catabolism; metabolism.) anaemia A condition in which the concentration of the oxygen-carrying pigment haemoglobin in the blood is below normal. Haemoglobin molecules are carried inside red blood cells and transport oxygen from the lungs to the tissues. Normally, stable haemoglobin concentrations in the blood are maintained by a balance between red-cell production in the bone marrow and red-cell destruction in the spleen. Anaemia may result if this balance is upset. Anaemia is not a disease but a feature of many different disorders. There are various types, which can be classified into those due to decreased or defective red-cell production by bone marrow (see anaemia, aplastic; anaemia, megaloblastic; anaemia, iron-deficiency) and those due to decreased survival of the red cells in the blood (see anaemia, haemolytic). The severity of symptoms depends on how low the haemoglobin concentration has become. Slightly reduced levels can cause headaches, tiredness, and lethargy. Severely reduced levels can cause breathing difficulty on exercise, dizziness, angina, and palpitations. General signs include pallor, particularly of the skin creases, the lining of the mouth, and the inside of the eyelids. Anaemia is diagnosed from the symptoms and by blood tests (see blood count; blood film). A bone marrow biopsy may be needed if the problem is with red blood cell production. anaemia, aplastic A rare but serious type of anaemia in which the red cells, white cells, and platelets in the blood are all reduced in number. Aplastic anaemia is caused by a failure of the bone marrow to produce stem cells, the initial form of all blood cells. Treatment of cancer with radiotherapy or anticancer drugs can temporarily interfere with the cell-producing ability of bone marrow, as can certain viral infections and other drugs. Long-term exposure to insecticides or benzene fumes may cause more persistent aplastic anaemia, and a moderate to high dose of nuclear radiation is another recognized cause. An autoimmune disorder is responsible in about half of all cases. Aplastic anaemia sometimes develops for no known reason. A low level of red blood cells may cause symptoms common to all types of anaemia, such as fatigue and breathlessness. White-cell deficiency increases susceptibility to infections; platelet deficiency may lead to a tendency to bruise easily, bleeding gums, and nosebleeds. The disorder is usually suspected from blood-test results, particularly a blood count, and is confirmed by a bone marrow biopsy. Blood and platelet transfusions can control symptoms. Immunosuppression is used to treat anaemia due to an autoimmune process. Severe persistent aplastic anaemia may be fatal unless a bone marrow transplant is carried out. anaemia, haemolytic A form of anaemia caused by premature destruction of red cells in the bloodstream (haemolysis). Haemolytic anaemias can be classified according to whether the cause of haemolysis is inside or outside the red cells. When haemolysis is due to a defect inside the red cells, the underlying problem is abnormal rigidity of the cell membrane. This causes the cells to become trapped, at an early stage of their life-span, in the small blood vessels of the spleen, where they are destroyed by macrophages (cells that ingest foreign particles). Abnormal rigidity may result from an inherited defect of the cell membrane (as in hereditary spherocytosis), a defect of the haemoglobin in the cell (as in sickle-cell anaemia), or a defect of one of the cell’s enzymes. An inherited deficiency of the glucose-6phosphate dehydrogenase enzyme (see 29 A