10/4/14

Anaesthesia general


Anaesthesia general
Anaesthesia general - Loss of sensation and consciousness induced to prevent the perception of pain throughout the body during surgery.

General anaesthesia is usually induced by intravenous injection of a barbiturate drug and maintained by inhalation of anaesthetic gases such as halothane, which may be introduced into the lungs via an endotracheal tube. During the anaesthetic, the pulse, blood pressure, and other vital signs are continuously monitored.

General anaesthetics have become much safer, and serious complications are rare. However, severe pre-existing diseases such as lung or heart disorders increase the risks. Minor after effects such as nausea and vomiting are usually controlled effectively with antiemetic drugs.

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Anaesthesia dental

Anaesthesia dental - Loss of sensation induced in a patient to prevent pain during dental treatment. For minor procedures, a local anaesthetic (see anaesthesia, local) is injected either into the gum at the site being treated or into the nerve a short distance away (called a peripheral nerve block).

In addition, topical anaesthetics are often used on the gums. For more complicated procedures, such as periodontal (gum) surgery and multiple tooth extractions, general anaesthesia is carried out (see anaesthesia, general).
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Anaesthesia

Anaesthesia - Absence of all sensation; insensibility. The term most commonly refers to anaesthesia that is induced artificially for medical purposes.

Two types of anaesthesia are used: local (see anaesthesia, local) and general (see anaesthesia, general). Damage to nerve tissues by injury or disease can produce anaesthesia in a localized area.
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Anaerobic

Anaerobic - Capable of living, functioning, and growing without oxygen. Many bacteria are anaerobic. Some human body cells are capable of limited anaerobic activity.

When muscular exertion is so strenuous that oxygen is used faster than the blood circulation can supply it, such as during sprinting, muscle cells temporarily work anaerobically. When this happens, lactic acid is produced as waste (instead of the carbon dioxide from aerobic activity), sometimes causing muscle fatigue and pain.

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Anaemia megaloblastic

Anaemia megaloblastic - An important type of anaemia caused by a deficiency of vitamin B12 or another vitamin, folic acid. Either of these deficiencies seriously interferes with production of red blood cells in the bone marrow. An excess of cells called megaloblasts appears in the marrow. Megaloblasts give rise to enlarged and deformed red blood cells known as macrocytes.

Vitamin B12 is found only in foods of animal origin, such as meat and dairy products. It is absorbed from the small intestine after first combining with intrinsic factor, a chemical produced by the stomach lining. The most common cause of vitamin B12 deficiency is failure of the stomach lining to produce intrinsic factor, usually due to an autoimmune disorder; this is called pernicious anaemia. Total gastrectomy (removal of the stomach) prevents production of intrinsic factor, and removal of part of the small intestine prevents B12 absorption, as does the intestinal disorder Crohn’s disease.

In a minority of cases, vitamin B12 deficiency is due to a vegan diet. Folic acid is found mainly in green vegetables and liver. The usual cause of deficiency is a poor diet. Deficiency can also be caused by anything that interferes with the absorption of folic acid from the small intestine (for example Crohn’s disease or coeliac disease). Folic acid requirements are greater than normal in pregnancy.

Many people with mild megaloblastic anaemia have no symptoms. Others may experience tiredness, headaches, a sore mouth and tongue, and mild jaundice. If B12 deficiency continues for a long time, additional symptoms due to nerve damage, including numbness and tingling in the feet, may develop.

Megaloblastic anaemia is diagnosed by blood tests and a bone marrow biopsy. Megaloblastic anaemia due to poor diet can be remedied with a short course of vitamin B12 injections or folic acid tablets and the introduction of a normal diet. A lifelong course of vitamin B12 injections or folic acid tablets is required if the underlying cause of malabsorption is untreatable.
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Anaemia iron-deficiency

Anaemia iron-deficiency - The most common form of anaemia caused by a deficiency of iron, an essential constituent of haemoglobin. The main cause of iron-deficiency anaemia is iron loss due to heavy or persistent bleeding; the most common cause in women of childbearing age is menstruation.

Other causes include blood loss from the digestive tract due to disorders such as erosive gastritis, peptic ulcer, stomach cancer, inflammatory bowel disease, haemorrhoids, and bowel tumours (see colon, cancer of). Prolonged use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) can cause gastrointestinal bleeding. In some countries, hookworm infestation of the digestive tract is an important cause of anaemia. Rarely, bleeding may also occur as a result of disorders of the urinary tract (such as kidney tumours or bladder tumours).

Iron deficiency may also be caused or worsened by lack of iron in, or its poor absorption from, the diet. The symptoms are those of the underlying cause, along with a sore mouth or tongue, and those common to all forms of anaemia, such as fatigue and breathlessness.

The diagnosis is made from blood tests and tests to look for an underlying cause. Treatment is given for the cause, along with a course of iron tablets or, very rarely, injections.
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Anaemia haemolytic

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-6- phosphate dehydrogenase enzyme (see G6PD deficiency) may result in episodes of haemolytic anaemia since the red cells are prone to damage by infectious illness or certain drugs or foods.

Haemolytic anaemias due to defects outside the red cells fall into 3 maingroups. First are disorders in which red cells are destroyed by buffeting (by artificial surfaces such as replacement heart valves, abnormal blood-vessel linings, or a blood clot in a vessel, for example). In the 2nd group, the red cells are destroyed
by the immune system. Immune haemolytic anaemias may occur if foreign blood cells enter the bloodstream, as occurs in an incompatible blood transfusion, or they may be due to an autoimmune disorder.

In haemolytic disease of the newborn, the baby’s red cells are destroyed by the mother’s antibodies crossing the placenta. Thirdly, the red cells may be destroyed by microorganisms; the most common cause is malaria. People with haemolytic anaemia may have symptoms common to all types of anaemia, such as fatigue and breathlessness, or symptoms specifically due to haemolysis, such as jaundice.

Diagnosis is made by examination of the blood (see blood film). Some inherited anaemias can be controlled by removing the spleen (see splenectomy). Others, such as G6PD deficiency, can be prevented by avoiding the drugs or foods that precipitate haemolysis.

Anaemias due to immune processes can often be controlled by immunosuppressant drugs. Transfusions of red cells are sometimes needed for emergency treatment of life-threatening anaemia.
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Anaemia aplastic

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.
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Anaemia

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.
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Anabolism

Anabolism - The manufacture of complex molecules, such as fats and proteins, from simpler molecules by metabolic processes in living cells. (See also catabolism; metabolism.)
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Amyotrophy

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).
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Amyloidosis

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.

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Amyl nitrite

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.
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Amylase

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.
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Amputation traumatic

Amputation traumatic - Loss of a finger, toe, or limb through injury. (See also microsurgery.)
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Amputation congenital

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.)
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Amputation

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 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.
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Ampulla

 Ampulla diagram
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.

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Ampicillin

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.
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Amphotericin B

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.
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Amoxicillin

Amoxicillin - A penicillin drug commonly used to treat a variety of infections, including bronchitis, cystitis, and ear and skin infections.

Allergy to amoxicilli causes a blotchy rash and, rarely, fever, swelling of the mouth and tongue, itching, and breathing difficulty.
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Amoxapine

Amoxapine - An antidepressant drug related to the tricyclics. Possible adverse effects include blurred vision, dizziness, drowsiness, abnormal muscular movements, menstrual irregularities, and breast enlargement.
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Amoebicides

Amoebicides - A group of drugs used to treat amoebiasis. Examples are diloxanide, and metronidazole.
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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.
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Amoeba

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.
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Amniotomy

Amniotomy - Artificial rupture of the amniotic membranes (breaking the “waters”) performed for induction of labour.
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Amniotic sac

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.
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Amniotic fluid

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.

Occasionally, excessive fluid is formed (see polyhydramnios); less frequently, insufficient amniotic fluid is formed (see oligohydramnios).
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Amnion

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.
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Amniocentesis


amniocentesis diagram
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 disorders such as haemophilia, cystic fibrosis, and Tay–Sachs disease.

Chemical 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.)
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Amniocentesis

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 disorders such as haemophilia, cystic fibrosis, and Tay–Sachs disease.

Chemical 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.)
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Amnesia

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.
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Ammonia

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.
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Amlodipine

Amlodipine - A calcium channel blocker drug used to prevent angina and to treat hypertension. Possible side effects are headaches and dizziness.
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Amitriptyline

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.
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Amiodarone

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.
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Aminophylline

Aminophylline - A bronchodilator drug used to treat chronic bronchitis, asthma, and, occasionally, heart failure. Nausea, vomiting, headache, dizziness, and palpitations are possible side effects.
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Aminoglycoside drugs

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.
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Aminoglutethimide

Aminoglutethimide - An anticancer drug used to treat certain types of breast cancer, prostate cancer, and some endocrine gland tumours.
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Amino acids

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.
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Amiloride

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.
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Amfetamine drugs

Amfetamine drugs - A group of stimulant drugs used mainly in the treatment of narcolepsy (a rare disorder characterized by excessive sleepiness). AMBIDEXTERITY AMFETAMINE DRUGS A 26 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.
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Amenorrhoea

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.
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Amelogenesis imperfecta

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.
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Ambulatory ECG

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.
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Ambulance

Ambulance - A vehicle for transporting sick or injured people that is staffed by trained personnel who can provide emergency treatment during the journey.
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Amblyopia

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.
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Ambidexterity

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.
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Amaurosis fugax

Amaurosis fugax - Brief loss of vision, lasting for seconds or minutes, usually affecting one eye only and caused by 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.
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Amantadine

Amantadine - An antiviral drug used in the prevention and treatment of influenza A and to help relieve symptoms of Parkinson’s disease.
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Amalgam dental

Amalgam dental - A material, consisting of an alloy of mercury with other metals, that is used as fillings for teeth (see filling, dental).
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