• granules
  • Human hair is composed largely of keratin and consists of a narrow central medulla surrounded by a thick envelope (cortex) of elongate cells, which contain numerous melanin granules that determine the natural color. (encyclopedia.com)
  • While hair color is closely related to the density of melanin granules, impairment in a person's health or substances in the diet that influence the availability of trace minerals are potential causes of changes in hair color or condition. (encyclopedia.com)
  • eumelanin
  • Two main forms of melanin exist in human skin - eumelanin and phaeomelanin, both of which are derived from tyrosine through the action of tyrosinase (a cupro-enzyme) and possibly other key enzymes (with nickel, chromium, iron, and manganese as cofactors). (encyclopedia.com)
  • coloration
  • The structural coloration of both the occipital and breast feathers of the bird-of-paradise Lawes' parotia is produced by melanin rodlets arranged in layers, together acting as interference reflectors. (pnas.org)
  • structures
  • Despite the great interspecific variation in the organization of such structures in bird plumage, melanin layers are usually considered too opaque, suggesting its main role is to delineate the outermost keratin layer and absorb incoherently scattered stray light. (royalsocietypublishing.org)
  • These results add to previous findings concerning the influence of melanin in single-layer iridescence, and stress the importance of considering natural variation when characterizing such photonic structures. (royalsocietypublishing.org)
  • thick
  • Structurally, the epidermis is only about a tenth of a millimeter thick but is made of 40 to 50 rows of stacked squamous epithelial cells. (innerbody.com)
  • Structurally, cephalodia consist of dense aggregates of Nostoc cells surrounded by thin-walled hyphae-this delimits them from the rest of the thallus which contains a loose structure of thick-walled hyphae. (wikipedia.org)
  • layer
  • To prevent an excessive blurring of the consciousness interval, melanin is present in the outer layer of the brain. (addforums.com)
  • brain
  • It is hypothesized that predilection of this species for the central nervous system is due to the presence of melanin, which may be able to cross the blood-brain barrier. (wikipedia.org)