British Medical Association ILLUSTRATED MEDICAL DICTIONARY 001-003_Prelims.indd 1 19/04/18 11:27 AM BRITISH MEDICAL ASSOCIATION Council Chair Dr Chaand Nagpaul Treasurer Dr Andrew Dearden Chair of Representative Body Dr Anthea Mowat CONTRIBUTERS AND CONSULTANTS BMA Consulting Medical Editor Dr Michael Peters Medical Consultants Dr Sue Davidson, Dr Dina Kaufman, Dr Nicola Renton, Dr Frances Williams DK LONDON Senior Editor Janet Mohun Project Art Editor Francis Wong Managing Editor Angeles Gavira Managing Art Editor Michael Duffy Jacket Editor Claire Gell Jacket Designer Stephanie Cheng Hui Tan Jacket Design Development Manager Sophia MTT Pre-production Producer David Almond Senior Producer Alex Bell Art Director Karen Self Associate Publishing Director Liz Wheeler Publishing Director Jonathan Metcalf Edited for DK by Martyn Page IMPORTANT READER NOTICE The British Medical Association Illustrated Medical Dictionary provides information on a wide range of medical topics, and every effort has been made to ensure that the information in this book is accurate and up-to-date (as at the date of publication). 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The BMA, BMA Consulting Medical Editor, consultants, contributors, editor, and publisher do not accept any legal responsibility for any personal injury or other damage or loss arising directly or indirectly from any use or misuse of the information and advice in this book. Fourth edition published in the United Kingdom in 2018 by Dorling Kindersley Limited, 80 Strand, London WC2R 0RL A Penguin Random House Company First edition published 2002 Second edition 2007, Third edition 2013 24681097531 001-308103-September/2018 Copyright © 2002, 2007, 2008, 2013, 2018 All rights reserved. No part of this publication may be reproduced, stored in or introduced into a retrieval system, or transmitted in any form, or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of the copyright owner. A CIP catalogue record for this book is available from the British Library. ISBN 978-0-2413-1771-6 Printed and bound in China A WORLD OF IDEAS: SEE ALL THERE IS TO KNOW www.dk.com 001-003_Prelims.indd 2 18/04/18 4:14 PM British Medical Association ILLUSTRATED MEDICAL DICTIONARY 001-003_Prelims.indd 3 18/04/18 4:14 PM A ABDOMEN A intake, eating unwisely, or an attack of diarrhoea. Pain in the lower abdomen is common during menstruation or in the middle of the menstrual cycle but is occasionally due to a gynaecological disorder such as endometriosis. Cystitis is a common cause of pain or discom­ fort in the abdomen. Bladder distension as a result of urinary obstruction may abdomen The region of the body between also cause abdominal pain. the chest and the pelvis. The abdominal Abdominal colic is pain that occurs cavity is bounded by the ribs and dia­ every few minutes as one of the internal phragm above, and by the pelvis below, organs goes into muscular spasm in an with the spine and abdominal muscles attempt to overcome an obstruction forming the back, side, and front walls. such as a stone or an area of inflamma­ It contains the liver, stomach, intes­ tion. The attacks of colic may become tines, appendix, spleen, pancreas, and more severe and may be associated kidneys. In the lower abdomen, enclosed with vomiting (see abdomen, acute). by the pelvis, are the bladder, rectum, Peptic ulcer often produces recurrent and, in women, the uterus and ovaries. gnawing pain. Other possible causes of abdominal pain are infection, such as ABDOMEN pyelonephritis, and ischaemia (lack of blood supply), as occurs when a volvu- Stomach lus (twisting of the intestine) obstructs Liver blood vessels. Tumours affecting an abdominal organ can cause pain. Abdo­ Large minal pain can also result from anxiety. intestine For mild pain, a wrapped hot­water bottle is often effective. Pain due to Area of peptic ulcer can be temporarily relieved abdomen Small by food or by taking antacid drugs. intestine Abdominal pain that is not relieved by vomiting, persists for more than 6 hours, Rectum or is associated with sweating or faint­ ing requires urgent medical attention. Urgent attention is also necessary if abdomen, acute Severe, persistent or pain is accompanied by persistent vom­ colicky ab dominal pain of sudden onset, iting, vomiting of blood, or passing of usually associated with spasm of the bloodstained or black faeces. Unex­ abdominal muscles, vomiting, and fever. plained weight loss or changes in bowel The most common cause of an acute habits should always be investigated. abdomen is peritonitis. Other causes Investigation of abdominal pain may include appendicitis, abdominal injury, include imaging techniques such as perforation of an internal organ due to ultrasound scanning and CT scanning, disorders such as peptic ulcer or diver- and endoscopy in the form of gastro- ticular disease. Acute abdominal pain scopy, colon oscopy, or laparoscopy commonly begins as a vague pain in the abdominal swelling Enlargement of centre but then becomes localized. the abdomen. It is a natural result of An acute abdomen requires urgent obesity and growth of the uterus during medical investigation that may involve pregnancy. Wind in the stomach or intes­ a laparoscopy or a laparotomy. Treat­ tine may cause uncomfortable bloating ment depends on the underlying cause. of the abdomen. Some women experi­ abdominal pain Discomfort in the ab ­ ence abdominal distension due to domen. Mild abdominal pain is common temporary water retention just before and is often due to excessive alcohol menstruation. Other causes may be 4 004-062_A_SPREADS.indd 4 08/06/18 2:29 PM ABRASION, DENTAL A ABDOMINAL THRUST abducent nerve The 6th cranial nerve. It supplies the lateral rectus muscle of Hands placed under each eye, which is responsible for mov- ribcage pull sharply ing the eyeball outwards. The nerve inwards and upwards originates in the pons (part of the brain- stem) 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. Mus- cles that carry out this movement are called abductors. (See also adduction.) ablation Removal or destruction of dis- eased tissue by excision (cutting away), cryosurgery (freezing), radiotherapy, dia thermy (burning), laser treatment, or radiofrequency ablation. abnormality A physical deformity or malformation, a behavioural or mental problem, or a variation from normal in the structure or function of a cell, tis- more serious. For instance, ascites (accu- sue, or organ in the body. mulation of fluid in the abdominal ABO blood groups See blood groups. cavity) may be a symptom of cancer or abortifacient An agent that causes abor- disease of the heart, kidneys, or liver; tion. In medical practice, abortion is swelling may also be due to intestinal induced using prostaglandin drugs. obstruction (see intestine, obstruction of) abortion In medical terminology, either or an ovarian cyst. spontaneous abortion (see miscarriage) Diagnosis of the underlying cause may or medically induced termination of involve abdominal X-rays, ultrasound pregnancy (see abortion, induced). scanning, laparotomy, or laparoscopy. In abortion, induced Medically induced ascites, fluid may be drained for analysis. termination of pregnancy. Abortion may abdominal thrust A first-aid treatment be performed if the pregnancy threatens for choking, in which sharp upward pres- the woman’s physical or emotional health sure is applied to the upper abdomen or if tests show a severe fetal abnormality. to dislodge a foreign body obstructing Depending on the stage of pregnancy, the airway. The technique is also some- termination may be induced by using times known as the Heimlich manoeuvre. drugs or by the surgical technique of abdominal X-ray An X-ray examina- vacuum suction curettage, under either tion of the abdominal contents. X-rays a general or local anaesthetic, during can show whether certain organs are which the fetal and placental tissues are enlarged and can detect swallowed for- removed. Complications are rare but eign bodies in the digestive tract. They may include infection, bleeding, and also show constipation and patterns of abdominal pain. fluid and gas: distended loops of bowel abrasion Also called a graze, a wound containing fluid often indicate an on the skin surface that is caused by obstruction (see intestine, obstruction scraping or rubbing. of); gas outside the intestine indicates abrasion, dental The wearing away of intestinal perforation. tooth enamel, often accompanied by the Calcium, which is opaque to X-rays, is erosion of dentine (the layer beneath present in most kidney stones (see cal- the enamel) and cementum (the bone- culus, urinary tract) and in some gallstones like tissue that covers the tooth root), and aortic aneurysms; these can some- usually through too-vigorous brushing. times be detected on an abdominal X-ray. Abraded areas are often sensitive to 5 004-062_A_SPREADS.indd 5 18/04/18 3:04 PM A ABREACTION cold or hot food or drink, and a desensi- abscess. Abscesses can also result from tizing toothpaste and/or protection with periodontal disease, in which bacteria a bonding agent (see bonding, dental) accumulate in pockets that form between or filling may be needed. the teeth and gums. abreaction In psychoanalysis, the pro- The affected tooth aches or throbs, cess of becoming consciously aware of and biting or chewing is usually repressed (buried) thoughts and feelings. extremely painful. The gum around the In Freudian theory, abreaction ideally tooth is tender and may be red and occurs by way of catharsis. swollen. An untreated abscess eventu- abscess A collection of pus formed as a ally erodes a sinus (channel) through result of infection by microorganisms, the jawbone to the gum surface, where usually bacteria. Abscesses may develop it forms a swelling known as a gumboil. in any organ and in the soft tissues As the abscess spreads, the glands in beneath the skin in any area. Common the neck and the side of the face may sites include the armpit, breast (see become swollen, and fever may develop. breast abscess), groin, and gums (see Treatment may consist of draining the abscess, dental). Rarer sites include the abscess, followed by root-canal treat- liver (see liver abscess) and the brain ment of the affected tooth, but in some (see brain abscess). cases extraction of the tooth is neces- Common bacteria, such as staphylo- sary. Antibiotics are prescribed if the cocci, are the usual cause of abscesses, infection has spread beyond the tooth. although fungal infections can cause An abscess in a periodontal pocket can them, and amoebae are an important usually be treated by the dentist scrap- cause of liver abscesses (see amoebiasis). ing away infected material. Infectious organisms usually reach inter- absence In medical terms, a temporary nal organs via the bloodstream, or they loss or impairment of consciousness penetrate tissues under the skin through that occurs in some forms of epilepsy, a wound or graze. typically generalized absence seizures in An abscess may cause pain, depending childhood. on where it occurs. Most larger abscesses absorption The process by which fluids cause fever, sweating, and malaise. Those or other substances are taken up by close to the skin often cause obvious red- body tissues. The term is commonly ness and swelling. applied to the uptake of the nutrients Antibiotics, antifungal drugs, or amoe- from food into blood and lymph from bicides are usually prescribed as the digestive tract. The major site of appropriate. Most abscesses also need absorption is the small intestine, which to be drained (see drain, surgical), and is lined with microscopic finger-like in some cases a tube may be left in projections called villi (see villus). place to allow continuous drainage. Some abscesses burst and drain spon- ABSCESS, DENTAL taneously. Occasionally, an abscess in a Enamel Decay vital organ damages enough surround- ing tissue to cause permanent loss of normal function, or even death. Dentine Gum abscess, dental A pus-filled sac in the tissue around the root of a tooth. An Pulp abscess may occur when bacteria invade the pulp (the tissues in the central cavity Blood of a tooth) as a result of dental caries, Nerve vessel which destroys the tooth’s enamel and dentine, allowing bacteria to reach the Jawbone pulp. Bacteria can also gain access to Abscess the pulp when a tooth is injured. The infection in the pulp then spreads into the surrounding tissue to form an 6 004-062_A_SPREADS.indd 6 18/04/18 3:04 PM ACETAZOLAMIDE A ACCOMMODATION Light rays from Point of Light rays from Point of near object focus distant object focus Rounded Ciliary lens bends Ciliary Flattened muscle the light muscle lens NEAR FOCUS DISTANT FOCUS These villi greatly increase the surface accidental death Death that occurs as area of the intestine, thereby increasing a direct result of an accident. A high pro- the rate of absorption. portion of deaths in young adults, acamprosate A drug used to help those particularly among males, are acciden- who are dependent on alcohol maintain tal. Many of these deaths are due to abstinence. Possible side effects include road traffic accidents, drowning, or drug diarrhoea, nausea, and abdominal pain. overdose. Falls in the home and burning Acamprosate is not generally advised for or asphyxiation due to fire are common those with kidney or severe liver damage. causes of accidental death in elderly acanthosis nigricans A rare condition people. Fatal accidents at work have in which thickened dark patches of skin become less common with the intro- appear in the groin, armpits, neck, and duction of effective safety measures. other skin folds. The condition may occur accommodation Adjustment, especially in young people as a genetic disorder or the process by which the eye adjusts as the result of an endocrine disorder itself to focus on near objects. At rest, such as Cushing’s syndrome. It also occurs the eye is focused for distant vision, in people with carcinomas of the lung when its lens is thin and flat. To make and other organs. focusing on a nearer object possible, the Pseudoacanthosis nigricans is a much ciliary muscle of the eye contracts, more common condition, usually seen which reduces the pull on the outer rim in dark-complexioned people who are of the lens, allowing it to become thick- overweight. In this form, the skin in fold er and more convex. areas is both thicker and darker than the With age, the lens loses its elasticity. surrounding skin, and there is usually This makes accommodation more and excessive sweating in affected areas. The more difficult and results in a form of condition may improve with weight loss. longsightedness called presbyopia. acarbose A drug used to treat type 2 acebutolol A beta-blocker drug used to diabetes mellitus. It acts on enzymes in treat hypertension, angina pectoris, and the intestines, inhibiting the digestion certain types of arrhythmia in which the of starch and slowing the rise in blood heart beats too rapidly. glucose levels after a carbohydrate meal. ACE inhibitor drugs A group of vaso- accessory nerve The 11th cranial nerve. dilator drugs used to treat heart failure, Unlike other cranial nerves, most of the hypertension, and diabetic nephropathy. accessory nerve originates from the spi- ACE (angiotensin converting enzyme) in- nal cord. The small part of the nerve that hibitors are often prescribed with other originates from the brain supplies mus- drugs, such as diuretic drugs or calcium cles of the palate, pharynx (throat), and channel blockers. Possible side effects larynx (voice-box). Damage to this part of include nausea, loss of taste, headache, the nerve may cause difficulty in speaking dizziness, and dry cough. and swallowing. The spinal part of the acetaminophen An analgesic drug nerve supplies large muscles of the neck more commonly known as paracetamol. and back, notably the sternomastoid and acetazolamide A drug used in the treat- trapezius. Damage to the spinal fibres of ment of glaucoma and, occasionally, to the nerve paralyses these muscles. treat epilepsy or to prevent or treat 7 004-062_A_SPREADS.indd 7 19/04/18 11:27 AM A ACETIC ACID symptoms of mountain sickness. Possible pressure in the oesophagus (see manom- adverse effects include lethargy, nausea, etry), and gastroscopy may be performed diarrhoea, and erectile dysfunction. to investigate achalasia. Oesophageal acetic acid The colourless, pungent, dilatation allows the oesophagus to be organic acid that gives vinegar its sour widened for long periods. Surgery to cut taste. In medicine, acetic acid is an some of the muscles at the stomach ingredient of preparations that are used entrance may be necessary. Other treat- for certain ear infections. ments may include medication and acetylcholine A type of neurotransmitter injection of botulinum toxin. (a chemical that transmits messages Achilles tendon The tendon that raises between nerve cells or between nerve the heel. The Achilles tendon is formed and muscle cells). It is the neurotrans- from the calf muscles (the gastrocnemi- mitter found at all nerve-muscle junctions us, soleus, and and at many other sites in the nervous plantar mus- ACHILLES TENDON system. The actions of acetylcholine are cles) and is Calf called cholinergic actions, and these can attached to the muscle be blocked by anticholinergic drugs. calcaneus (heel- acetylcholinesterase inhibitors A bone). Minor group of drugs used in the treatment of injuries to the mild to moderate dementia due to Alz- Achilles tendon heimer’s disease, in which there is a are common Achilles deficiency of the neurotransmitter ace- and can result tendon tylcholine in the brain. Drugs such as in inflammation donepezil and rivastigmine work by (tendinitis). Vio- blocking the action of acetylcholinester- lent stretching ase, the enzyme in the brain responsible of the tendon for the breakdown of acetylcholine. This can cause it to raises acetylcholine levels and can slow rupture; in such Heel the rate of progression of dementia in cases, surgical some patients. These drugs have no effect repair may be on dementia due to other causes, such as necessary. stroke or head injury, however. Common achlorhydria Absence of stomach acid side effects include nausea, diarrhoea, secretions. This may be due to chronic dizziness, and headache. Rarely, difficulty atrophic gastritis or to an absence or in passing urine may occur. Those taking malfunction of acid-producing parietal acetylcholinesterase inhibitors require cells in the stomach lining. Achlorhydria regular medical monitoring. may not produce symptoms but is asso- acetylcysteine A drug used in the treat- ciated with stomach cancer, however, ment of paracetamol overdose. When the and is a feature of pernicious anaemia drug is taken in large doses, vomiting or (see anaemia, megaloblastic). rash may occur as rare side effects. achondroplasia A rare genetic disor- achalasia A rare condition of unknown der of bone growth that leads to short cause in which the muscles at the lower stature. The condition is caused by a end of the oesophagus and the sphincter dominant gene (see genetic disorders) (valve) between the oesophagus and the but often arises as a new mutation. The stomach fail to relax to let food into the long bones of the arms and legs are stomach after swallowing. As a result, affected mainly. The cartilage that links the lowest part of the oesophagus is nar- each bone to its epiphysis (the growing rowed and becomes blocked with food, area at its tip) is converted to bone too while the part above widens. Symptoms early, preventing further limb growth. include difficulty and pain with swallow- Those affected have short limbs, a well- ing and pain in the lower chest and developed trunk, and a head of normal upper abdomen. size except for a protruding forehead. A chest X-ray, barium swallow (a type aciclovir An antiviral drug that can be of barium X-ray examination), measuring taken by mouth, used topically, or given 8 004-062_A_SPREADS.indd 8 18/04/18 3:04 PM