the area of the retina that allows fine details to be observed at the centre of vision; also refers to any small, flat spot on the skin

Macular degeneration

gradual loss of vision due to deterioration of nerve tissue in the retina


a mineral that is essential for many body functions, including nerve impulse transmission, formation of bones and teeth, and muscle contraction

Magnetic resonance imaging (MRI)

a technique that uses magnetic fields and radio waves to create high-quality cross-sectional images of the body without using radiation


an impaired ability of the lining of the small intestine to absorb nutrients from food


a parasitic disease spread by mosquitoes that causes chills and fever; potentially fatal complications in the liver, kidneys, blood, and brain are possible


abnormal development of an organ or tissue


a word used to describe a condition that is characterised by uncontrolled growth and/or that can be fatal, such as a cancerous tumour

Malignant hyperthermia

a reaction to certain anaesthesia gases involving intense muscle contractions and a high fever

Malignant melanoma

the most serious type of skin cancer, in which a mole changes shape, darkens, becomes painful, and/or bleeds easily

Mallory-Weiss syndrome

a condition associated with alcoholism in which the lower end of the oesophagus tears, causing vomiting of blood


an X-ray procedure done to detect breast cancer


a general term for a cosmetic operation on the breasts; includes breast reduction, enlargement, and reconstruction after a mastectomy


another term for the lower jaw


a mental disorder characterised by extreme excitement, happiness, over-activity, and agitation; usually refers to the high of the highs and lows experienced in manic-depressive disorder

Manic-depressive disorder

a mental disorder characterised by extreme mood swings, including either mania, depression, or a continuing shift between the two extremes

MAO inhibitor

see Monoamine oxidise inhibitor antidepressant

Marfan's syndrome

a rare genetic disorder that affects connective tissue, leading to abnormalities of joints, bones, tendons, ligaments, arteries, and/or the heart

Mast cell

a type of cell present in most body tissues that releases substances in response to an allergen, which causes symptoms such as inflammation


a surgical procedure in which all or part of the breast is removed to prevent the spread of cancer


inflammation of the breast, which is usually caused by a bacterial infection


one of two bones that form the upper jaw, the roof of the mouth, and the centre portion of the face


an illness caused by a viral infection, causing a characteristic rash and a fever; primarily affects children


thick, sticky, greenish-brown stool passed by a post-mature foetus, or one experiencing foetal distress, into the amniotic fluid, or by an infant during the first couple of days after birth


a term used to describe something situated on or near the midline of the body or a body structure

Median nerve

a nerve running down the arm to the hand; controls muscle movement in the forearm and hand and conveys sensation from part of the hand


investigation of the central chest compartment using an endoscope that is inserted through an incision in the neck


the centre part of an organ or body structure; sometimes used to refer to the lower part of the brain stem


a type of cancerous tumour, occurring in the section of the brain that controls posture and balance; found mainly in children


a severely swollen large intestine, causing severe constipation and abdominal bloating; may be present at birth or develops later

Megaloblastic anaemia

a type of anaemia in which a lack of the vitamin B12 or folic acid interferes with red blood cells and causes them to be enlarged and deformed, resulting in tiredness and weight loss


the type of cell division that occurs only in the ovaries and testicles, producing cells with half the genes of the original cell; these cells then form eggs and sperm


the pigment that gives skin, hair, and eyes their colouring

Melanocyte-stimulating hormone

a hormone that co-ordinates pigmentation of the skin, eyes, and hair


cells that produce the pigment melanin


a skin tumour composed of cells called melanocytes


the beginning of menstruation

Meniere's disease

a disorder of the inner ear, causing hearing loss, ringing in the ear, and the sensation that one's surroundings are spinning


the three membranes that surround and protect the spinal cord and brain


a rare noncancerous tumour developing in the protective membranes covering the brain called the meninges; can cause headaches and problems with vision and mental function


inflammation of the meninges; usually caused by infection by a micro-organism (meningitis caused by bacteria is life-threatening; viral meningitis is milder)


a protrusion of the meninges through an opening in the skull or spinal cord due to a genetic defect


surgical removal of all or part of a cartilage disk from a joint


a crescent-shaped pad of cartilage in joints that helps to reduce friction


the period in a woman's life when menstruation stops, resulting in a reduced production of oestrogen and cessation of egg production


excessive loss of blood during menstruation, which can be caused by disorders of the uterus

Menstrual cycle

the periodic discharge of blood and mucosal tissue from the uterus, occurring from puberty to menopause in a woman who is not pregnant


the shedding of the lining of the uterus during the menstrual cycle

Mesenteric infarction

death of tissue in the intestine due to lack of blood supply to that tissue

Mesenteric lymphadenitis

inflammation of lymph nodes in an abdominal membrane


a cancerous tumour occurring in the lining of the lungs and chest cavity, often associated with exposure to asbestos dust


a tissue layer that lines the heart, abdomen, chest cavity, and lungs

Messenger RNA

an RNA molecule that transports the information stored in DNA out of a cell's nucleus in order to make proteins

Metabolic rate

the speed at which the body uses energy


a general term for all of the chemical processes that occur in the body


any substance that takes part in a chemical reaction in the body


the spreading of a cancerous tumour to another part of the body through lymph, blood, or across a cavity; also sometimes refers to a tumour that has been produced in this way

Metered-dose inhaler

an inhaler that gives a specific amount of medication with each use


any tiny, single-celled organism (such as a bacterium, virus, or fungus)


another term for a micro-organism, especially one that causes disease


the study of micro-organisms


an abnormally small head


surgical removal of the protruding part of a prolapsed disk


a surgical technique that uses a special binocular microscope to operate on tiny, delicate, or hard-to-reach tissues

Micturition syncope

fainting or feeling weak while standing at the toilet; caused by an abnormal heartbeat or a drop in blood pressure

Middle ear

the small cavity between the eardrum and inner ear; contains three tiny, linked bones that transmit sound to the inner ear

Middle ear effusion

the build-up of fluid in the middle ear, which can affect hearing


a profession concerned with providing care to a mother and baby during pregnancy and childbirth


a severe headache, usually accompanied by vision problems and/or nausea and vomiting, and that typically recurs


a substance that is a necessary part of a healthy diet (such as potassium, calcium, sodium, phosphorus, and magnesium)


an oral contraceptive containing only the synthetic hormone progesterone (birth control pills contain oestrogen and progesterone)


a drug that causes the pupil to constrict


expulsion of a foetus before it has developed sufficiently to survive on its own


small eight-legged animals, many of which burrow and feed on blood


the process by which most cells divide in order to reproduce

Mitral insufficiency

a problem with the ability of the mitral valve in the heart to close, which causes the heart to pump harder and reduces its efficiency

Mitral stenosis

a condition in which the mitral valve in the heart becomes narrowed, making the heart work harder to pump blood; can lead to symptoms such as shortness of breath

Mitral valve

the valve in the heart that allows blood to flow from the left atrium to the left ventricle, but prevents blood from flowing back in

Mitral valve prolapse

a common condition in which the mitral valve in the heart is deformed, causing blood to leak back across the valve; characterised by a heart murmur and sometimes chest pain and disturbed heart rhythm

Modified radical mastectomy

a treatment for breast cancer in which the entire breast, a section of the chest muscle, and lymph nodes in the chest and underarm are removed

Molar tooth

large, strong teeth at the back of the jaw, primarily used to grind food


a brown to dark-brown spot on the skin that can be flat or raised


the smallest unit of a substance that possesses its characteristics

Molluscum contagiosum

a viral infection that causes white bumps on the skin; usually clears up in a few months

Mongolian spot

a brown to blue-black spot on the lower back and buttocks at birth, caused by a concentration of pigment-producing cells; usually disappears by the age of 3 or 4 years

Monoamine oxidise inhibitor antidepressant

a substance that works by stopping an enzyme that breaks down stimulating chemicals in the brain; used to treat depression

Monoclonal antibodies

an antibody that is produced in the laboratory so that it will react with only one specific foreign protein; used to help diagnose certain kinds of cancer


an infection caused by a virus that invades a type of white blood cell called a monocyte, causing fever, sore throat, and swollen lymph nodes

Monounsaturated fat

a type of fat that is thought to be beneficial in the prevention of coronary heart disease; found in foods such as olive oil and peanut oil


the state of being ill or having a disease

Morning sickness

nausea and vomiting experienced early in a pregnancy, affecting about half of all pregnant women


the death rate, measured as the number of deaths per a certain population; may describe the population as a whole, or a specific group within a population (such as infant mortality)

Motor nerve

a nerve that carries messages to a muscle that cause the muscle to contract

Motor neurone disease

degeneration of the nerves in the spinal cord and brain that are responsible for muscle movement, causing weakness and muscle deterioration

Mouth-to-mouth resuscitation

a method of artificial breathing in which someone rhythmically forces air into the lungs of a person who has stopped breathing


see Magnetic resonance imaging


see Multiple sclerosis


a sac or body cavity that is swollen because of the production of mucus by the cells in its lining


a drug that lessens the sticky quality of phlegm and makes it easier to cough up

Mucous membrane

the soft, pink layer of cells that produce mucus in order to keep body structures lubricated; found in structures such as the eyelids, respiratory tract, and urinary tract


a slippery fluid produced by mucous membranes that lubricates and protects the internal surfaces of the body

Multi-infarct dementia

dementia caused by multiple strokes

Multiple myeloma

a cancer that causes uncontrolled production of white blood cells in the bone marrow

Multiple pregnancy

the presence of more than one foetus in the uterus, such as occurs with twins

Multiple sclerosis

a disease in which the protective coverings (myelin) of nerve fibres in the brain are gradually destroyed; symptoms vary from numbness to paralysis and loss of control of bodily function

Multiple-gated acquisition scan

a technique for evaluating heart efficiency by measuring blood flow into and out of the heart


a viral infection that causes inflammation of salivary glands; primarily affects children


a characteristic sound (heard through a stethoscope) of blood flowing irregularly through the heart; can be harmless or may be an indication of disease

Muscle fibres

specialised, contracting cells that are bundled together to form muscles

Muscle relaxants

a group of drugs used to relieve muscle spasm and to treat conditions such as arthritis, back pain, and nervous system disorders such as stroke and cerebral palsy

Muscle tone

the natural tension in resting muscles

Muscle wasting

the degeneration of a muscle (loss of bulk), caused by disease or starvation

Muscular dystrophy

a rare genetic disorder in which muscles degenerate gradually and strength is lost


anything that can increase the rate of abnormal change in cells, which can lead to cancer


a change in the genetic information within a cell


the medical term for muscle pain

Myasthenia gravis

a disease in which the muscles, mainly those in the face, eyes, throat, and limbs, become weak and tire quickly; caused by the body's immune system attacking the receptors in the muscles that pick up nerve impulses


a type of slow-growing bacterium; resistant to the body's defence mechanisms and are responsible for diseases such as tuberculosis and leprosy


the smallest free-living micro-organisms


any disease caused by a fungus


a drug that causes the pupil to dilate (widen)

Myelin sheath

the fat


inflammation of the spinal cord, which can cause headaches, fever, muscle stiffness, pain, weakness, and eventually paralysis


protrusion of the spinal cord and its coverings out from the spine; one of the more severe forms of spina bifida


a cancer affecting cells in the bone marrow; sometimes used as an abbreviation for multiple myeloma


build-up of fibrous connective tissue in the bone marrow, affecting the production of blood components

Myocardial infarction

the death of an area of heart muscle as a result of being deprived of its blood supply; characterised by severe pain in the chest; commonly called a heart attack


inflammation of the heart muscle, which can be caused by a virus, certain drugs, or radiation therapy


the medical term for heart muscle


the surgical removal of a noncancerous tumour from muscle


a muscle disease, usually one that results in the deterioration of muscle


the medical term for near-sightedness


muscle inflammation, causing pain and weakness


a surgical opening in the eardrum that allows for drainage


a noncancerous tumour made of mucous material and fibrous connective tissue

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