aqueous cream - An emollient preparation that is commonly used to treat dry, scaly, or itchy skin in conditions such as eczema.
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10/9/14
APUD cell tumour
APUD cell tumour - A growth composed of cells that produce various hormones. These cells, amine precursor uptake and decarboxylation (APUD) cells, occur in different parts of the body.
Some tumours of the thyroid gland, pancreas, and lungs are APUD cell tumours, as are a carcinoid tumour (see carcinoid syndrome) and phaeochromocytoma (a type of adrenal tumour).
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Some tumours of the thyroid gland, pancreas, and lungs are APUD cell tumours, as are a carcinoid tumour (see carcinoid syndrome) and phaeochromocytoma (a type of adrenal tumour).
apraxia
apraxia - An inability to carry out purposeful movements despite normal muscle power and coordination. Apraxia is caused by damage to nerve tracts in the cerebrum (the main mass of the brain) that translate the idea for a movement into an actual movement.
Damage to the cerebrum may be caused by a head injury, infection, stroke, or brain tumour. There are various forms of apraxia, each related to damage in different parts of the brain.
A person with ideomotor apraxia is unable to carry out a spoken command to make a particular movement, but at other times can make the same movement unconsciously. In sensory apraxia, a person may not be able to use an object due to loss of ability to recognize its purpose.
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Damage to the cerebrum may be caused by a head injury, infection, stroke, or brain tumour. There are various forms of apraxia, each related to damage in different parts of the brain.
A person with ideomotor apraxia is unable to carry out a spoken command to make a particular movement, but at other times can make the same movement unconsciously. In sensory apraxia, a person may not be able to use an object due to loss of ability to recognize its purpose.
appetite suppressants
appetite suppressants - A group of drugs that reduce the desire to eat. Appetite suppressants may be used in the treatment of severe obesity, along with diet and exercise. Their use is limited to a maximum of 12 weeks due to the risk of serious effects on the blood supply to the lungs and on heart valves.
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appetite stimulants
appetite stimulants - Various tonics and remedies traditionally prescribed to stimulate the appetite. None are proven to be effective. Some drugs such as corticosteroids may stimulate the appetite when used to treat unrelated disorders.
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appetite loss
appetite loss of - Loss of appetite is usually temporary and due to an emotional upset or minor illness. Persistent loss of appetite may have a more serious underlying cause, such as chronic infection or cancer.
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appetite
appetite - A desire for food; a pleasant sensation felt in anticipation of eating. Appetite, which is regulated by 2 parts of the brain (the hypothalamus and the cerebral cortex), is learned by enjoying a variety of foods that smell, taste, and look good. It combines with hunger to ensure that the right amount of a wide range of foods is eaten to stay healthy. (See also appetite, loss of.)
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appendix
The appendix has no known function, but it contains a large amount of lymphoid tissue which provides a defence against local infection. The position of an individual’s appendix partly determines the set of symptoms produced by acute appendicitis (inflammation of the appendix).
appendicitis
appendicitis - Acute inflammation of the appendix. The cause is usually not known, but appendicitis is sometimes caused by obstruction of the appendix by a lump of faeces.
The 1st symptom is usually vague discomfort around the navel. Within a few hours, this develops into severe, more localized pain, which is usually most intense in the lower righthand side of the abdomen. Symptoms may differ if the appendix is not in the most common position. For example, if the appendix impinges on the ureter, the urine may become bloodstained.
The usual treatment for appendicitis is appendicectomy, which is often performed endoscopically (see minimally invasive surgery). If the treatment is delayed, an inflamed appendix may burst, releasing its contents into the abdomen. This leads to peritonitis and, in some cases, an abscess.
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The 1st symptom is usually vague discomfort around the navel. Within a few hours, this develops into severe, more localized pain, which is usually most intense in the lower righthand side of the abdomen. Symptoms may differ if the appendix is not in the most common position. For example, if the appendix impinges on the ureter, the urine may become bloodstained.
The usual treatment for appendicitis is appendicectomy, which is often performed endoscopically (see minimally invasive surgery). If the treatment is delayed, an inflamed appendix may burst, releasing its contents into the abdomen. This leads to peritonitis and, in some cases, an abscess.
appendicectomy
appendicectomy - Surgical removal of the appendix to treat acute appendicitis.
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apoptosis
apoptosis - The natural process of programmed cell death. Apoptosis occurs in embryonic development, when the shaping of body parts is taking place and continues throughout life in the constant cycle of death and renewal of body cells. Failure of apoptosis is implicated in the development of cancers.
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aponeurosis
aponeurosis - A wide sheet of tough, fibrous tissue that acts as a tendon, attaching a muscle to a bone or a joint.
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apolipoprotein
apolipoprotein - A group of proteins that are constituents of lipoproteins, the carriers of fat in the bloodstream. Apolipoproteins are also involved in the growth and repair of nerve tissues.
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apocrine gland
apocrine gland - A gland that discharges cellular material in addition to the fluid it secretes. The term is usually applied to the type of sweat glands that appear in hairy body areas after puberty. (See also eccrine gland.)
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apnoea
apnoea - Cessation of breathing, either temporarily or for a prolonged period. Breathing is an automatic process controlled by the respiratory centre in the brainstem. Failure of this centre to maintain normal breathing is known as central apnoea. It may occur in babies, particularly those who are premature, and can be detected by an apnoea alarm.
Central apnoea can also result from brainstem damage, for example following a stroke or head injury. In obstructive apnoea, breathing is prevented by a blockage in the airway. The most common type is sleep apnoea, in which blockage of the upper airway occurs repeatedly during sleep.
Deliberate temporary apnoea occurs in breath-holding attacks. Another type of apnoea occurs in Cheyne–Stokes respiration, in which cycles of deep, rapid breathing alternate with episodes of breathing stoppage.
Treatment of apnoea depends on the cause. In newborn babies, it resolves as they mature. In stroke or head injury, artificial ventilation may be needed temporarily until recovery occurs.
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Central apnoea can also result from brainstem damage, for example following a stroke or head injury. In obstructive apnoea, breathing is prevented by a blockage in the airway. The most common type is sleep apnoea, in which blockage of the upper airway occurs repeatedly during sleep.
Deliberate temporary apnoea occurs in breath-holding attacks. Another type of apnoea occurs in Cheyne–Stokes respiration, in which cycles of deep, rapid breathing alternate with episodes of breathing stoppage.
Treatment of apnoea depends on the cause. In newborn babies, it resolves as they mature. In stroke or head injury, artificial ventilation may be needed temporarily until recovery occurs.
aplasia
aplasia - Absent or severely reduced growth and development of any organ or tissue. For example, in bone marrow aplasia, the rate of cell division in the bone marrow is reduced, leading to insufficient blood-cell production (see anaemia, aplastic). Some birth defects, such as stunted limbs (see phocomelia), occur as a result of incomplete tissue formation during prenatal development.
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apicectomy
apicectomy - Surgical removal of the tip of a tooth root. Apicectomy may be performed as part of root-canal treatment.
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aphrodisiac
aphrodisiac - Any substance that is thought to stimulate erotic desire and enhance sexual performance. For centuries, various substances (most notably oysters and rhinoceros horn) have been used as aphrodisiacs. In fact, no substance has a proven aphrodisiac effect.
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aphasia
aphasia - A complete absence of previously acquired language skills, caused by a brain disorder that affects the ability to speak and write, and/or the ability to comprehend and read. Related disabilities that may occur in aphasia are alexia (word blindness) and agraphia (writing difficulty).
Language function in the brain lies in the dominant cerebral hemisphere (see cerebrum). Two particular areas in this hemisphere, Broca’s and Wernicke’s areas, and the pathways connecting the two, are important in language skills. Damage to these areas, which most commonly occurs as a result of stroke or head injury, can lead to aphasia.
Some recovery from aphasia is usual following a stroke or head injury, although the more severe the aphasia, the less the chances of recovery. Speech therapy is the main treatment. (See also dysphasia; speech; speech disorders.)
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Language function in the brain lies in the dominant cerebral hemisphere (see cerebrum). Two particular areas in this hemisphere, Broca’s and Wernicke’s areas, and the pathways connecting the two, are important in language skills. Damage to these areas, which most commonly occurs as a result of stroke or head injury, can lead to aphasia.
Some recovery from aphasia is usual following a stroke or head injury, although the more severe the aphasia, the less the chances of recovery. Speech therapy is the main treatment. (See also dysphasia; speech; speech disorders.)
aphakia
aphakia - The absence of the lens from the eye. Aphakia may be congenital, may result from surgery (for example, cataract surgery), or may be due to a penetrating injury.
Aphakia causes severe loss of focusing in the affected eye and requires correction by implanting a lens or with contact lenses or glasses.
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Aphakia causes severe loss of focusing in the affected eye and requires correction by implanting a lens or with contact lenses or glasses.
Apgar score
aortography
aortography - An imaging technique that enables the aorta (the main artery of the body) and its branches to be seen clearly on X-ray film following injection of a contrast medium (a substance that is opaque to X-rays). Aortography is used if surgery is needed to treat an aneurysm (ballooning of the aorta).
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aortitis
aortitis - Inflammation of the aorta (the main artery of the body). Aortitis is a rare condition that occurs in people with arteritis or untreated syphilis and in some people with ankylosing spondylitis.
Aortitis may cause part of the aorta to widen and its walls to become thinner. This may lead to an aneurysm (ballooning of the artery). Aortitis may damage the ring around the aortic valve in the heart, leading to aortic incompetence.
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Aortitis may cause part of the aorta to widen and its walls to become thinner. This may lead to an aneurysm (ballooning of the artery). Aortitis may damage the ring around the aortic valve in the heart, leading to aortic incompetence.
aortic stenosis
The most common cause of aortic stenosis is deposition of calcium on the aortic valve, usually associated with atherosclerosis. Aortic stenosis may also be caused by a congenital abnormality.Aortic stenosis may not cause symptoms. When symptoms do occur, they include fainting, lack of energy, chest pain on exertion due to angina, and breathing difficulty.
Chest X-ray, ECG, and echocardiography may be carried out to diagnose aortic stenosis. A cardiac catheter can be used to demonstrate the degree of stenosis (see catheterization, cardiac). Heart-valve surgery may be needed to widen or replace the damaged valve.
aortic incompetence
aortic incompetence - Leakage of blood through the aortic valve (one of the heart valves), resulting in a backflow of blood from the aorta into the left ventricle (the heart’s main pumping chamber).
Failure of the aortic valve to close properly may be due to a congenital abnormality in which the valve has 2 flaps rather than 3.
The valve leaflets can be destroyed by infective endocarditis. Aortic incompetence is associated with ankylosing spondylitis, and Marfan’s syndrome. Atherosclerosis may damage the valve, causing a combination of aortic stenosis and incompetence.
Aortic incompetence is also found in untreated syphilis, which is now rare. Aortic incompetence may not cause symptoms and is sometimes found during a routine medical examination. The heart compensates for the backflow of blood into the left ventricle by working harder, which may eventually lead to heart failure; this causes breathing difficulty and oedema (fluid accumulation).
Chest X-ray, ECG, and echocardiography may be carried out to diagnose aortic incompetence. A cardiac catheter is sometimes used to demonstrate the degree of incompetence (see catheterization, cardiac).
Heart failure resulting from aortic incompetence can be treated with diuretic drugs. Heart-valve surgery to replace the damaged valve may eventually be necessary.
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Failure of the aortic valve to close properly may be due to a congenital abnormality in which the valve has 2 flaps rather than 3.
The valve leaflets can be destroyed by infective endocarditis. Aortic incompetence is associated with ankylosing spondylitis, and Marfan’s syndrome. Atherosclerosis may damage the valve, causing a combination of aortic stenosis and incompetence.
Aortic incompetence is also found in untreated syphilis, which is now rare. Aortic incompetence may not cause symptoms and is sometimes found during a routine medical examination. The heart compensates for the backflow of blood into the left ventricle by working harder, which may eventually lead to heart failure; this causes breathing difficulty and oedema (fluid accumulation).
Chest X-ray, ECG, and echocardiography may be carried out to diagnose aortic incompetence. A cardiac catheter is sometimes used to demonstrate the degree of incompetence (see catheterization, cardiac).
Heart failure resulting from aortic incompetence can be treated with diuretic drugs. Heart-valve surgery to replace the damaged valve may eventually be necessary.
aorta
It terminates in the abdomen by dividing into the 2 common iliac arteries of the legs. The aorta is thick-walled and has a large diameter in order to cope with the high pressure and large volume of blood passing through it. (See also arteries, disorders of; circulatory system.)
anxiety disorders
anxiety disorders - A group of mental illnesses, including several specific syndromes, in which symptoms of anxiety are the main feature. These disorders are common and mainly affect young adults.
In generalized anxiety disorder, there is persistent tension and apprehension that has no specific focus or cause, together with physical or psychological symptoms that disrupt normal activity.
Panic disorders are characterized by sudden attacks of extreme, unreasonable anxiety. Phobias are irrational fears, such as the fear of open spaces or spiders, that lead to avoidance of certain situations or objects.
Counselling, psychotherapy, and group or individual cognitive–behaviour therapy are used to treat anxiety disorders. Antianxiety drugs (especially benzodiazepine drugs) may be used for shortterm treatment but are addictive.
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In generalized anxiety disorder, there is persistent tension and apprehension that has no specific focus or cause, together with physical or psychological symptoms that disrupt normal activity.
Panic disorders are characterized by sudden attacks of extreme, unreasonable anxiety. Phobias are irrational fears, such as the fear of open spaces or spiders, that lead to avoidance of certain situations or objects.
Counselling, psychotherapy, and group or individual cognitive–behaviour therapy are used to treat anxiety disorders. Antianxiety drugs (especially benzodiazepine drugs) may be used for shortterm treatment but are addictive.
anxiety
anxiety - An unpleasant emotional state ranging from mild unease to intense fear. Various physical symptoms are associated with anxiety; the most common include palpitations, chest pains, a feeling of tightness in the chest, and a tendency to overbreathe (see hyperventilation).
Muscle tension leads to headaches and back pains. Gastrointestinal symptoms include dry mouth, bloating, diarrhoea, nausea, and difficulty in swallowing. Other symptoms include sweating, blushing, pallor, lightheadedness, and a frequent need to urinate or defaecate.
Anxiety is a normal response to stressful situations and prepares the mind and body to respond effectively. However, anxiety that occurs without reason may be a symptom of an anxiety disorder or another psychological disorder such as depression.
People suffering from anxiety may be helped by counselling or psychotherapy. If there is an underlying disorder such as depression, treatment with antianxiety drugs can help. Antianxiety drugs are used for short-term control of symptoms but are avoided for long-term treatment because they are addictive.
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Muscle tension leads to headaches and back pains. Gastrointestinal symptoms include dry mouth, bloating, diarrhoea, nausea, and difficulty in swallowing. Other symptoms include sweating, blushing, pallor, lightheadedness, and a frequent need to urinate or defaecate.
Anxiety is a normal response to stressful situations and prepares the mind and body to respond effectively. However, anxiety that occurs without reason may be a symptom of an anxiety disorder or another psychological disorder such as depression.
People suffering from anxiety may be helped by counselling or psychotherapy. If there is an underlying disorder such as depression, treatment with antianxiety drugs can help. Antianxiety drugs are used for short-term control of symptoms but are avoided for long-term treatment because they are addictive.
anus imperforate
anus imperforate - A rare congenital abnormality in which the anal opening is missing or covered over.
The severity of the condition varies from complete absence of the anal canal to only a layer of skin covering the anal opening.
Treatment involves surgery. A colostomy may be needed initially before definitive surgery to construct an anus.
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The severity of the condition varies from complete absence of the anal canal to only a layer of skin covering the anal opening.
Treatment involves surgery. A colostomy may be needed initially before definitive surgery to construct an anus.
anus disorders
anus, disorders of - Most anal disorders affect adults and are minor, but they may cause discomfort. Rarely, the anus may fail to develop normally and surgical treatment is needed (see anus, imperforate). In anal stenosis, the anus is too narrow to allow the passage of faeces.
Anal fissures originate from tears in the lining of the anus, usually as a result of straining to pass faeces. Cancer of the skin around the anus is rare (see anus, cancer of).
Haemorrhoids are enlarged blood vessels under the anal lining. An anal fistula is an abnormal channel connecting the anal canal with the skin surrounding the anus.
Itching of the anus is common and may be due to haemorrhoids or other disorders such as threadworm infestation.
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Anal fissures originate from tears in the lining of the anus, usually as a result of straining to pass faeces. Cancer of the skin around the anus is rare (see anus, cancer of).
Haemorrhoids are enlarged blood vessels under the anal lining. An anal fistula is an abnormal channel connecting the anal canal with the skin surrounding the anus.
Itching of the anus is common and may be due to haemorrhoids or other disorders such as threadworm infestation.
anus cancer
anus cancer of - A rare cancer of the skin of the anus. Possible early signs are development of swelling or an ulcer at the anus accompanied by bleeding and discomfort. Treatment is by surgical removal and/or radiotherapy.
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anuria
anuria - Complete cessation of urine output. Anuria may be caused by a severe malfunction of the kidneys, but a more common cause is a complete blockage of urine flow, due to enlargement of the prostate gland (see prostate, enlarged), a bladder tumour, or a stone (see calculus, urinary tract).
Failure of the kidneys to produce urine may be due to oxygen depletion as a result of reduced blood flow through the kidneys, as occurs in shock, or to severe kidney damage caused by a disease such as glomerulonephritis.
Anuria requires urgent investigation. Treatment of the cause may restore urine production, but any delay can result in permanent kidney damage, leading to uraemia.
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Failure of the kidneys to produce urine may be due to oxygen depletion as a result of reduced blood flow through the kidneys, as occurs in shock, or to severe kidney damage caused by a disease such as glomerulonephritis.
Anuria requires urgent investigation. Treatment of the cause may restore urine production, but any delay can result in permanent kidney damage, leading to uraemia.
antral irrigation
antral irrigation - Irrigation of the maxillary antrum, one of the nasal sinuses. More commonly known as sinus washout, this procedure is used to diagnose and treat persistent sinusitis.
Antral irrigation is performed less often since the introduction of nasal endoscopy.
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Antral irrigation is performed less often since the introduction of nasal endoscopy.
antiviral drugs
antiviral drugs - Drugs used in the treatment of infection by viruses. No drugs have been developed that can eradicate viruses, and at present immunization is the most effective way of preventing serious viral infections.
However, antiviral drugs can reduce the severity of some viral infections (most notably herpes, influenza, viral hepatitis, and cytomegalovirus infections), particularly in people who have reduced immunity. Advances have also been made in the treatment of HIV infection (see antiretroviral drugs).
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However, antiviral drugs can reduce the severity of some viral infections (most notably herpes, influenza, viral hepatitis, and cytomegalovirus infections), particularly in people who have reduced immunity. Advances have also been made in the treatment of HIV infection (see antiretroviral drugs).
antitoxin
antitoxin - Any of a variety of commercially prepared substances containing antibodies that can combine with and neutralize the effect of a specific toxin released into the bloodstream by particular bacteria.
Antitoxins are usually given by injection into a muscle. Occasionally, an antitoxin may cause an allergic reaction (see allergy).
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Antitoxins are usually given by injection into a muscle. Occasionally, an antitoxin may cause an allergic reaction (see allergy).
antithyroid drugs
antithyroid drugs - Drugs used to treat hyperthyroidism, in which the thyroid gland is overactive. They may be used as the sole treatment or before thyroid surgery. Carbimazole and propylthiouracil interfere with the production of thyroid hormone by the gland.
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antispasmodic drugs
antispasmodic drugs - A group of drugs that relax spasm in smooth muscle in the wall of the intestine or bladder.
These drugs are used to treat irritable bowel syndrome and irritable bladder. Possible side effects include dry mouth, blurred vision, and difficulty in passing urine. (See also anticholinergic drugs.)
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These drugs are used to treat irritable bowel syndrome and irritable bladder. Possible side effects include dry mouth, blurred vision, and difficulty in passing urine. (See also anticholinergic drugs.)
antisocial personality disorder
antisocial personality disorder - Impulsive, destructive behaviour that often disregards the feelings and rights of others. People who have an antisocial personality lack a sense of guilt and cannot tolerate frustration.
They may have problems with relationships and are frequently in trouble with the law. Behaviour therapy, and various forms of psychotherapy, may help to improve integration. In general, the effects of this disorder decrease with age.
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They may have problems with relationships and are frequently in trouble with the law. Behaviour therapy, and various forms of psychotherapy, may help to improve integration. In general, the effects of this disorder decrease with age.
antiserum
antiserum - A preparation containing antibodies (also known as immunoglobulins) that combine with specific antigens (foreign proteins), usually components of microorganisms, leading to deactivation or destruction of the microorganisms.
Antiserum is usually used, along with immunization, as an emergency treatment when someone has been exposed to a dangerous infection such as rabies and has not previously been immunized.
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Antiserum is usually used, along with immunization, as an emergency treatment when someone has been exposed to a dangerous infection such as rabies and has not previously been immunized.
antiseptics
antiseptics - Chemicals applied to the skin in order to destroy bacteria and other microorganisms, thereby preventing infection.
Common antiseptics are chlorhexidine, cetrimide, hexachlorophene, and compounds containing iodine. (See also disinfectants; aseptic technique.)
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Common antiseptics are chlorhexidine, cetrimide, hexachlorophene, and compounds containing iodine. (See also disinfectants; aseptic technique.)
antirheumatic drugs
antirheumatic drugs - A group of drugs used to treat rheumatoid arthritis and types of arthritis that are caused by other autoimmune disorders such as systemic lupus erythematosus.
Antirheumatic drugs affect the disease process and may limit joint damage, unlike nonsteroidal anti-inflammatory drugs, which only relieve pain and stiffness.
The main antirheumatic drugs are corticosteroid drugs, immunosuppressant drugs, chloroquine, gold, penicillamine, and sulfasalazine.
Many of these drugs can have serious side effects, and treatment must be under specialist supervision.
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Antirheumatic drugs affect the disease process and may limit joint damage, unlike nonsteroidal anti-inflammatory drugs, which only relieve pain and stiffness.
The main antirheumatic drugs are corticosteroid drugs, immunosuppressant drugs, chloroquine, gold, penicillamine, and sulfasalazine.
Many of these drugs can have serious side effects, and treatment must be under specialist supervision.
antiretroviral drugs
antiretroviral drugs - Drugs that are used to slow or halt the spread of viruses in people with HIV infection and AIDS. There are 3 main groups: reverse transcriptase inhibitors, protease inhibitors, and non-nucleoside reverse transcriptase inhibitors.
Drugs from different groups are often used in combination. Antiretroviral drugs can have a range of side effects, including nausea, vomiting, diarrhoea, tiredness, and a range of effects on blood chemistry, particularly involving fats.
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Drugs from different groups are often used in combination. Antiretroviral drugs can have a range of side effects, including nausea, vomiting, diarrhoea, tiredness, and a range of effects on blood chemistry, particularly involving fats.
antipyretic drugs
antipyretic drugs - Drugs that reduce fever. Examples of antipyretic drugs include paracetamol, aspirin, and other non-steroidal anti-inflammatory drugs
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antipsychotic drugs
antipsychotic drugs - A group of drugs used to treat psychoses (mental disorders involving loss of contact with reality), particularly schizophrenia and mania in bipolar disorder (see manic– depressive illness).
Antipsychotic drugs may also be used to sedate people who have other mental disorders (such as dementia) and who are very agitated or aggressive. Antipsychotics include phenothiazine drugs, butyrophenones, such as haloperidol, and several new drugs including risperidone, which is used to treat the symptoms of mania.
Antipsychotics can cause drowsiness, lethargy, dyskinesia, and parkinsonism. Other possible side effects include dry mouth, blurred vision, and difficulty in passing urine. However, newer drugs may have fewer side effects when used in the long term.
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Antipsychotic drugs may also be used to sedate people who have other mental disorders (such as dementia) and who are very agitated or aggressive. Antipsychotics include phenothiazine drugs, butyrophenones, such as haloperidol, and several new drugs including risperidone, which is used to treat the symptoms of mania.
Antipsychotics can cause drowsiness, lethargy, dyskinesia, and parkinsonism. Other possible side effects include dry mouth, blurred vision, and difficulty in passing urine. However, newer drugs may have fewer side effects when used in the long term.
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