Dictionary

Body systems

Anatomy and the conditions of each body system, from the heart and lungs to the skin.

MHCMajor histocompatibility complex: a group of genes that make the markers cells use to show the immune system what is self and what is not.

MIAn abbreviation most often meaning myocardial infarction (heart attack); it can also mean mitral insufficiency or motivational interviewing.

micronutrientA vitamin or mineral that the body needs in small amounts to work and grow normally.

midlineAn imaginary line down the center of the body; also, a type of IV catheter placed in a vein of the upper arm.

migraineA long-term neurological disorder that causes repeated attacks of moderate to severe headache.

miliaTiny, white, raised bumps on the skin, most often on a newborn's nose, chin and cheeks.

mineralA natural element, such as calcium, iron or potassium, that the body needs in small amounts.

mineralocorticoidA steroid hormone, or a drug that acts like one, that makes the kidneys keep sodium and water and remove potassium.

mitosisCell division that makes two new cells, each with the same full set of chromosomes as the original.

mitral valveThe heart valve between the left atrium and the left ventricle.

mobilityThe ability to move freely and easily, such as turning in bed, getting up and walking.

moleA small, usually brown spot or bump on the skin made of a cluster of pigment cells.

Mongolian spotsFlat, blue-gray patches of skin present at birth, now called congenital dermal melanocytosis.

Montgomery tuberclesSmall raised bumps on the areola, the darker skin around the nipple.

moodA person's inner emotional state that lasts over time, as the person describes it.

mood disorderA mental health condition in which a person's mood is far lower or higher than usual for a long time.

morbidityThe state of having a disease or health problem, or how often a disease occurs in a group of people.

Moro reflexA newborn reflex in which a sudden noise or loss of support makes the baby fling the arms out and then bring them back in.

motilityThe ability to move on its own, such as the movement of food through the gut or the swimming of sperm.

motor neuronA nerve cell that carries signals from the brain or spinal cord out to a muscle to make it move.

mucosaThe moist lining of body passages that open to the outside, such as the mouth, nose, gut and bladder.

mucousRelating to mucus or making mucus, as in mucous membrane.

mucous membraneThe moist lining of body openings and passages, such as the mouth, nose, eyelids, gut and airways.

mucusThe thick, slippery fluid made by mucous membranes that moistens and protects them.

multiple myelomaA cancer of plasma cells, the white blood cells that make antibodies, that grows in the bone marrow.

multiple sclerosisA long-term disease in which the immune system damages the protective covering of nerves in the brain and spinal cord.

mumpsA contagious disease caused by the mumps virus that mainly infects the salivary glands in front of the ears.

murmurAn extra whooshing or swishing sound heard with a stethoscope over the heart, made by turbulent blood flow.

muscularRelating to the muscles, or having well-developed muscles.

musculoskeletalHaving to do with the muscles, bones, joints, tendons and ligaments.

mutationA change in the genetic code (DNA) of a cell.

myastheniaWeakness of the muscles.

myasthenia gravisA long-term autoimmune disease in which antibodies block the signals passing from nerves to muscles.

myelinThe fatty covering wrapped around many nerve fibers that protects them and speeds up their signals.

myocardial infarctionDeath of part of the heart muscle because its blood supply is blocked; a heart attack.

myocardiumThe thick middle layer of the heart wall, made of heart muscle that contracts to pump blood.

myopathyA disease of the muscle tissue itself.

myopiaNearsightedness: close things are seen clearly but distant things look blurred.