Dictionary

meibomitis See meibomianitis.

meibomianitis Inflammation of the little glands in the tarsus of the eyelids. Chronic inflammation of these glands can lead to a lump in the eyelid known as a chalazion. Also known as meibomitis.

megavitamin therapy The use of massive doses of vitamins to treat disease. Because overuse of vitamins can cause disease, most physicians consider megavitamin therapy controversial. See also Appendix C, “Vitamins”; orthomolecular medicine; vitamin therapy.

megakaryocyte A giant cell in the bone marrow that is the ancestor of blood platelets, which are essential to normal blood clotting.

megacolon An abnormally enlarged colon. Megacolon can arise as a serious congenital problem in the newborn, caused by abnormal innervation of the colon and frequently requiring surgery.

mega- Prefix meaning abnormally large, as in megalocephaly (an overly large head) and megacardia (an enlarged heart).

MEDVAC Acronym for medical evacuation. MED-VAC typically refers to a team that has the skills necessary for proper medical evacuation in emergency situations. Also known as MEDEVAC.

medulloblastoma A type of brain tumor that tends to occur in children, arise in the cerebellum (in the lower part of the brain), and spread along the spine. Medulloblastoma is the most common type of primary brain tumor in childhood. Medulloblastomas occasionally metastasize outside the central nervous system, usually to bone. Treatment involves surgery, radiotherapy,…

medulla oblongata The base of the brain, which is formed by the enlarged top of the spinal cord. The medulla oblongata directly controls breathing, blood flow, and other essential functions.

medulla, adrenal The innermost portion of the adrenal gland, which makes epinephrine (adrenaline) and norepinephrine (noradrenaline). These hormones cause the breakdown of the storage product glycogen to the sugar glucose in the liver, facilitate the release of fatty acids from adipose (fat) tissue, cause narrowing (constriction) of most blood vessels in the body, and increase…

medulla The innermost part. For example, the adrenal medulla is the innermost part of the adrenal gland, the renal medulla is the inner part of the kidney, and the spinal medulla is the part of the spinal cord that is lodged deep within the vertebral canal.

MEDLINE The best-known bibliographic database of the US National Library of Medicine (NLM), which lets anyone with computer access query the NLM’s store of journal references on specific topics. The MEDLINE database covers the fields of medicine, nursing, dentistry, veterinary medicine, the health care system, and the preclinical sciences. MEDLINE is part of the MEDLARS…