metabolism

metabolism The whole range of biochemical processes that occur within a living organism. Metabolism consists of anabolism (the buildup of substances) and catabolism (the breakdown of substances). The term metabolism is commonly used to refer specifically to the breakdown of food and its transformation into energy.

metabolic disease

metabolic disease A metabolism disorder, such as albinism, cystinuria, phenylketonuria (PKU), and some forms of gout, sun sensitivity, and thyroid disease. There are hundreds of known metabolic diseases. Advances in the diagnosis and treatment of metabolic diseases have improved the outlook for many of these conditions so that early diagnosis, if possible in infancy, can…

mesothelioma

mesothelioma A malignant tumor of the mesothelium, the thin lining of the surface of the body cavities and the organs that are contained within them. Most mesotheliomas begin as one or more nodules that progressively grow to form a solid coating of tumor surrounding the lung, abdominal organs, or heart. Mesothelioma occurs most commonly in…

mesoderm

mesoderm The middle of the three primary germ cell layers (the other two being the ectoderm and endoderm) that make up a very young embryo. The mesoderm differentiates (specializes) to give rise to a number of tissues and structures, including bone, muscle, connective tissue, and the middle layer of the skin. See also differentiation; ectoderm;…

mesentery

mesentery In general, a fold of tissue that attaches organs to the body wall. The word mesentery usually refers to the small bowel mesentery, which anchors the small intestines to the back of the abdominal wall. Blood vessels, nerves, and lymphatics branch through the mesentery to supply the intestine. Other mesenteries exist to support the…

mercury poisoning

mercury poisoning Disease resulting from exposure to the metallic element mercury. Mercury is toxic to humans, and poisoning can occur in both acute and chronic forms. Acute mercury poisoning (less common) is associated with ulcerations of the stomach and intestine and with toxic changes in the kidney. Chronic mercury poisoning can cause diarrhea, slowed reflexes,…

mental retardation

mental retardation The condition of having an IQ measured as below 70 to 75 and significant delays or lacks in at least two areas of adaptive skills. Mental retardation is present from childhood. Between 2 and 3 percent of the general population meet the criteria for mental retardation. Causes of mental retardation include fetal alcohol…

mental illness

mental illness Any disease that affects the central nervous system, causing disturbances of thought or behavior. Mental illnesses can be caused by genetic, metabolic, structural, infectious, or environmental causes. The term mental illness is also used to describe emotional disturbances caused by traumatic or distressing events or by poor adjustment to normal life stresses. Treatment…