The part of the brain that contains myelinated nerve fibers. The white matter is white because it is the color of myelin, the insulation that covers nerve fibers.
- White phosphorus
A waxy solid which burns easily and is used in chemical manufacturing and smoke munitions. It is also used by industry to produce phosphoric acid and other chemicals for use in fertilizers, food additives, and cleaning compounds. Small amounts of white phosphorus were used in the past in pesticides and fireworks. Breathing white phosphorus for […]
- White spots on the nails
Very small semi-circular white spots on the nails. These spots may be found on the fingernails and, particularly, the toenails. The white spots on the nails reflect injury to the base (matrix) of the nail. The matrix is the part under the visible nail where the nail cells and the nail itself are produced. The […]
- White subungual onychomycosis, proximal
The rarest form of fungus infection of the finger or toenail. (Fungus infection of the finger or toenail is also called onychomycosis.) The infection begins in the nail fold (the portion of the nail opposite the tip of the finger). Proximal white subungual onychomycosis is typically associated with HIV infection (AIDS), though it can follow […]
- White coat hypertension
A transient increase in blood pressure (hypertension) that is triggered by the sight of medical personnel in white coats (or other attire). Ideally, people so affected should do their best to relax when in the medical office.
A familiar term for what is medically called a closed comedo. A comedo, the primary sign of acne, consists of a dilated (widened) hair follicle filled with keratin squamae (skin debris), bacteria, and sebum (oil). A whitehead is a comedo that has an obstructed opening to the skin. A closed comedo may rupture and cause […]