Dictionary

mitotic Pertaining to mitosis.

mitotic nondisjunction The failure in mitosis for the two members of a chromosome pair to separate (to disjoin) normally so that both chromosomes go to one daughter cell while none go to the other daughter cell. See also mitosis.

mitral insufficiency A malfunction of the mitral valve that permits the backflow of blood (regurgitation) from the left ventricle into the left atrium. Most mitral insufficiency is mild and requires no treatment. When severe, however, treatment with medications and sometimes surgery is necessary.

mitral prolapse See mitral valve prolapse.

mitral regurgitation Backflow of blood from the left ventricle to the left atrium due to mitral valve insufficiency.

mitral valve A valve in the heart that is situated between the left atrium and the left ventricle. The mitral valve permits blood to flow from the left atrium into the left ventricle, but not in the reverse direction. The mitral valve has two flaps (cusps). It is so named because it looks like a…

mitral valve, aorta, skeleton, and skin syndrome See MASS syndrome.

mitral valve prolapse A common heart valve anomaly affecting 5–10 percent of people that involves prolapse (flopping backwards) of the mitral valve leaflets into the left atrium during contraction of the heart’s ventricles. This sometimes allows leakage of blood through the valve opening (mitral regurgitation). Most people with mitral valve prolapse have no symptoms, however,…

mittelschmerz Pain due to ovulation that usually occurs at the midpoint between the menstrual periods. From the German mittel, meaning “middle,” and schmerz, meaning “pain.”

mixed connective tissue disease A mixture of three diseases of connective tissue (the framework for the cells of the body): systemic lupus erythematosus, scleroderma, and polymyositis. Patients with mixed connective tissue disease typically have features of each of these three component diseases. They also typically have very high blood levels of antinuclear antibodies (ANAs) and…

mixed mania A state of mind that is characterized by symptoms of both mania and depression and is seen in bipolar disorders. Mixed mania is more common in bipolar children and women than in men. A person experiencing mixed mania may feel agitated, angry, irritable, and depressed all at once. Because it combines a high…

MMR Measles, mumps, rubella vaccine, a combination vaccine.