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The word skin originally only referred to dressed and tanned animal hide and the usual word for human skin was hide. Skin is a borrowing from Old Norse skinn "animal hide, fur", ultimately from the Proto-Indo-European root *sek-, meaning "to cut" (probably a reference to the fact that in those times animal hide was commonly cut off to be used as garment).
The integumentary system is the set of organs forming the outermost layer of an animal's body. It comprises the skin and its appendages, which act as a physical barrier between the external environment and the internal environment that it serves to protect and maintain the body of the animal. Mainly it is the body's outer skin.
Micrograph of keratinocytes, basal cells and melanocytes in the epidermis Keratinocytes (stained green) in the skin of a mouse. Keratinocytes are the primary type of cell found in the epidermis, the outermost layer of the skin. In humans, they constitute 90% of epidermal skin cells. [1]
Cell Biology in "The Biology Project" of University of Arizona. Centre of the Cell online; The Image & Video Library of The American Society for Cell Biology Archived 2011-06-10 at the Wayback Machine, a collection of peer-reviewed still images, video clips and digital books that illustrate the structure, function and biology of the cell.
Melanin (/ ˈ m ɛ l ə n ɪ n / ⓘ; from Ancient Greek μέλας (mélas) ' black, dark ') is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. [1] Melanin pigments are produced in a specialized group of cells known as melanocytes.
The principle function of epithelial tissues are covering and lining of free surface; The cells of the body's surface form the outer layer of skin. Inside the body, epithelial cells form the lining of the mouth and alimentary canal and protect these organs. Epithelial tissues help in the elimination of waste.
These pigments have protective functions in the skin and aid in the sense of sight in the retina, but their function in neurons is not understood completely. Furthermore, cardiac tissue and central nervous system neurons show a yellow to brown pigment called lipofuscin, believed by some to have lysosomal activity. [4]
The third type is the xanthophores which contains yellow pigments in the forms of carotenoids. The various colors are made by the combination of the different layers of the chromatophores. These cells are usually located beneath the skin or scale the animals. There are two categories of colors generated by the cell – biochromes and ...