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Melanocytes are melanin-producing neural crest-derived [3] cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea), [4] the inner ear, [5] vaginal epithelium, [6] meninges, [7] bones, [8] and heart found in many mammals and birds. [9] Melanin is a dark pigment primarily responsible ...
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.
In mammals, the auditory hair cells are located within the spiral organ of Corti on the thin basilar membrane in the cochlea of the inner ear. They derive their name from the tufts of stereocilia called hair bundles that protrude from the apical surface of the cell into the fluid-filled cochlear duct .
Deflections of the stereocilia in the opposite direction toward the shortest stereocilia causes transduction channels to close. In this situation, the hair cells become hyperpolarized and the nerve afferents are not excited. [7] [8] [9] There are two different types of fluid that surround the hair cells of the inner ear.
The height of hair bundles increases from base to apex and the number of stereocilia decreases (i.e. hair cells located at the base of the cochlea contain more stereo cilia than those located at the apex). [14] Furthermore, in the tip-link complex of cochlear hair cells, tonotopy is associated with gradients of intrinsic mechanical properties. [15]
Freckles are clusters of concentrated melaninized cells which are most easily visible on people with a fair complexion.Freckles do not have an increased number of the melanin-producing cells, or melanocytes, but instead have melanocytes that overproduce melanin granules (melanosomes) changing the coloration of the outer skin cells (keratinocytes).
Fish and frog melanophores are cells that can change colour by dispersing or aggregating pigment-containing melanosomes. A melanosome is an organelle found in animal cells and is the site for synthesis, storage and transport of melanin, the most common light-absorbing pigment found in the animal kingdom.
The cortex of the hair shaft is located between the hair cuticle and medulla and is the thickest hair layer. It contains most of the hair's pigment, giving the hair its color. The major pigment in the cortex is melanin, which is also found in skin. The distribution of this pigment varies from animal to animal and person to person.