- : A substance that gives color to tissue. Pigments are responsible for the color of skin, eyes, and hair.
* * *1. Any coloring matter, as that of the red blood cells, hair, iris, etc., or the stains used in histologic or bacteriologic work, or that in paints. 2. A medicinal preparation for external use, applied to the skin like paint, or coloring agents used in paints. [L. pigmentum, paint]- bile pigments coloring matter in the bile derived from porphyrins by rupture of a methane bridge; e.g., bilirubin, biliverdin.- chymotropic p. a p. dissolved in the vacuole of a plant cell. [G. chymos, juice, + trope, turning, inclination, + -ic]- formalin p. a p. formed when acid aqueous solutions of formaldehyde act on blood-rich tissues; characterized by rotation of the plane of polarized light, withstanding extraction in aqueous and lipid solvents, being bleached in acids and hydrogen peroxide; not formed when tissue is fixed with formaldehyde buffered to pH levels above 6.- malarial p. a dark brown, granular p. that rotates the plane of polarized light and has other properties similar to formalin p.; occurs in parasites, such as Plasmodium malariae, around brain capillaries, and in fixed macrophages of spleen, liver, bone marrow, and lymph node s; composed of excess protein, an iron porphyrin, and hematin left over from the metabolism of hemoglobin by the malarial parasite within the red blood cell. See malarial p. stain.- natural p. a naturally occurring colored compound; absorbs light in the visible range of the electromagnetic spectrum. Cf.:structural color. SYN: biochrome.- respiratory pigments the oxygen-carrying (colored) substances in blood and tissues (hemoglobin, myoglobin, hemocyanin, etc.).- visual pigments the photopigments in the retinal cones and rods that absorb light and initiate the visual process.- wear-and-tear p. lipofuscin that accumulates in aging or atrophic cells as a residue of lysosomal digestion.
* * *pig·ment 'pig-mənt n a coloring matter in animals and plants esp. in a cell or tissue also any of various related colorless substances
* * *n.a substance giving colour. Physiologically important pigments include the blood pigments (especially haemoglobin), bile pigments, and retinal pigment (see rhodopsin). The pigment melanin occurs in the skin and in the iris of the eye. Important plant pigments include chlorophyll and the carotenoid.
* * *pig·ment (pigґmənt) [L. pigmentum paint] 1. any normal or abnormal coloring matter of the body. 2. a paintlike medicinal preparation to be applied to the skin.
Medical dictionary. 2011.