The prefix “melan-” derives from the Greek word “melas,” meaning black or dark. It appears in medical and biological terms to denote dark pigmentation or color, as in melanin (dark skin pigment) and melanoma (malignant tumor of melanocytes). Origin and Etymology This prefix stems from ancient Greek “μέλας” (mélas), signifying black or dark hue. In…
melancholia An old term for depression.
melanin The pigment that gives human skin, hair, and eyes their color. Dark-skinned people have more melanin in their skin than light-skinned people have. Melanin is produced by cells called melanocytes. It provides some protection again skin damage from the sun, and the melanocytes increase their production of melanin in response to sun exposure. Freckles,…
melanocyte A cell in the skin that produces and contains the pigment melanin.
Meckel diverticulum See diverticulum, Meckel.
meconium Dark, sticky material that is normally present in the intestine at birth and passed in the feces after birth, after trypsin and other enzymes from the pancreas have acted on it. The passage of meconium before birth can be a sign of fetal distress.
meconium ileus Obstruction of the intestine (ileus) due to overly thick meconium. Meconium ileus results from a deficiency of trypsin and other digestive enzymes from the pancreas, as in cystic fibrosis.
medial collateral ligament of the knee The ligament that straps the inner side of the knee joint, providing stability and strength. See also knee.
medial meniscus of the knee A thickened, crescent-shaped cartilage pad in the inner portion of the joint formed by the femur (the thigh bone) and the tibia (the shin bone). The medial meniscus is in the inner side, whereas the lateral meniscus is in the outer side of this knee joint. The meniscus acts as…
median The middle, as in the median strip in a highway. For example, the median nerve is the nerve the runs through the middle of the wrist.
mediastinoscopy A procedure in which the physician inserts a tube into the chest to view the organs in the mediastinum. The tube is inserted through an incision above the breastbone.
mediastinotomy The surgical opening of the mediastinum. See also mediastinum; mediastinoscopy.