10/2/14

Aggression

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.
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aggregation platelet

Aggregation platelet - The clumping together of platelets (small, sticky blood AFFECTIVE DISORDERS AGGREGATION, PLATELET A 16 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.
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ageusia

ageusia - The lack or an impairment of the sense of taste (see taste, loss of).
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Age spots

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.
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Agent Orange

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).
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Agent

Agent - Any substance or force capable of bringing about a biological, chemical, or physical change. (See also reagent.)
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Agenesis

Agenesis - The complete absence at birth of an organ or bodily component, caused by failure of development in the embryo.
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Age

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.

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Agar

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.
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Agammaglobulinaemia

Agammaglobulinaemia - A type of immunodeficiency disorder in which there is almost complete absence of B-lymphocytes and immunoglobulins in the blood.
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Afterpains

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.
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Afterbirth

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.
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Aflatoxin

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.
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Affinity

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.
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Affective disorders

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.)
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Affect

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 in moods may have an affective disorder. Shallow or reduced affect may be a sign of schizophrenia or of an organic brain syndrome.
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Aetiology

Aetiology - The cause of a disease or the study of the various factors involved in causing a disease.
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Aerophagy

Aerophagy - Excessive swallowing of air, which may occur during rapid eating or drinking or be caused by anxiety.
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Aerodontalgia

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.
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Aerobics

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.)
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Aerobic

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.
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Adrenal tumours

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:phaeochromocytoma and neuroblastoma, which affects children. These tumours cause intermittent hypertension and sweating attacks. Surgical removal of a tumour usually cures these conditions.
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Adrenaline

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.
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Adrenal hyperplasia congenital

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.
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Adrenal gland disorders

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.
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Adrenal glands

structure of Adrenal 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.
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Adrenal failure

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.
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ADP

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.)
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Adolescence

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.
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Adlerian theory

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.)
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Adjuvant

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.
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Adipose 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, and abdomen; in women, it occurs on the breasts, hips, and thighs.

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Adhesion

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.
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ADHD

ADHD - The abbreviation for attention deficit hyperactivity disorder.
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ADH

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.
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Adenomatos

Adenomatos - is 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.
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Adenoma

Adenoma - A noncancerous tumour or cyst that resembles glandular tissue and arises from the epithelium (the layer of cells that lines the inside of 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.
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Adenoids

Adenoids overview
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.

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.

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Adenoidectomy

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.
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Adenocarcinoma

Adenocarcinoma - The technical name for a cancer of a gland or glandular tissue, or for a cancer in which the cells 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.)

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Adenitis

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.
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Adduction

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.)
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Addison’s disease

Addison’s disease - A rare chronic disorder in which there is a deficiency of 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.
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Addiction

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.)
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ADD

ADD - The abbreviation for attention deficit disorder, more commonly known as attention deficit hyperactivity disorder.
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Adams apple

Adams 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.
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Acute

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.)
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Acupuncture

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) flowsthrough 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.
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Acupressure

Acupressure - A derivative of acupuncture in which pressure is applied instead of needles.
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Actinomycosis

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 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.
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Actinic

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).
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Acting out

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.
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Actin

Actin - A protein involved in muscle contraction, in which microscopic filaments of actin and another protein, myosin, slide in between each other.
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