mosaic A person or a tissue that contains two or more types of genetically different cells. All females are mosaics because of X-chromosome inactivation (lyonization). Mosaic patterns can affect the way genetic disorders are expressed. For example, about 5 percent of people with Down syndrome have a mosaic variant in which only some cells have…
mortality 1 The condition of being mortal, of eventually having to die. The opposite of mortality is immortality. 2 The rate of death.
Morquio syndrome A form of mucopolysaccharidosis that is characterized by an inability to break down keratan sulfate, which leads to abnormal accumulation of keratan sulfate in muscle and skeletal tissues. This in turn can lead to abnormalities of the skeleton, muscles, skin, teeth, and muscular organs. Diagnosis is made by examining leukocytes and cultured skin…
morphology 1 Literally, the study of form (structure). 2 A form itself.
morphine A powerful narcotic agent that has strong analgesic (pain relief) action and other significant effects on the central nervous system. It is dangerously addicting. Morphine is a naturally occurring member of a large chemical class of compounds called alkaloids. The name, which derives from Morpheus (the mythologic god of dreams) was coined in 1805…
morphea Skin changes that are localized to one or more patchy areas of skin that become hardened, dry, smooth, and slightly pigmented. Morphea is called “localized scleroderma” but it rarely, if ever, evolves into full-fledged scleroderma, an autoimmune disease of the connective tissue.
morning-after pill See contraceptive, emergency.
morning sickness The common phenomenon of nausea between the 6th and 12th weeks of pregnancy. Symptoms include nausea and vomiting. Morning sickness is believed to be caused by hormonal changes and metabolic changes that involve carbohydrate digestion. Suggested treatment includes eating crackers or other high-carbohydrate foods first thing in the morning (even before getting out…
morgue A place where dead bodies are kept before autopsy, funeral, or burial.
morbilli See measles.
morbidity Illness, disease.
monozygous twins Identical twins. They are called monozygous because they originate from a single fertilized egg (zygote).