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The medulla is the innermost layer of the hair shaft. This nearly invisible layer is the most soft and fragile, and serves as the pith or marrow of the hair. Some mammals don't have a medulla in their hair. The presence or absence of this layer and the characteristics of the medulla can aid taxonomists in identifying what taxa a hair comes from.
Diagram of the hair shaft, indicating medulla (innermost), cortex, and cuticle (exterior.) Anatomy of hair. 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 ...
The hair cuticle is also known to contain anteiso-18-methyleicosanoic acid which contribute to the hydrophobic properties of hair. [5] [4] Diagram of the hair shaft, indicating medulla (innermost), cortex, and cuticle (exterior) While the cuticle is the outermost layer, it is not responsible for the color of the hair.
The Fischer–Saller scale, named after Eugen Fischer and Karl Saller is used in physical anthropology and medicine to determine the shades of hair color. The scale uses the following designations: A (very light blond), B to E (light blond), F to L (), M to O (dark blond), P to T (light brown to brown), U to Y (dark brown to black) and Roman numerals I to IV and V to VI (red-blond).
In mammalian outer hair cells, the varying receptor potential is converted to active vibrations of the cell body. This mechanical response to electrical signals is termed somatic electromotility; [13] it drives variations in the cell's length, synchronized to the incoming sound signal, and provides mechanical amplification by feedback to the traveling wave.
The process of hair growth occurs in distinct sequential stages: anagen is the active growth phase, catagen is the regression of the hair follicle phase, telogen is the resting stage, exogen is the active shedding of hair phase and kenogen is the phase between the empty hair follicle and the growth of new hair. [1] The function of hair in ...
Medulla of the thymus, a part of the lobes of the thymus; Medulla of lymph node; Medulla (hair), the innermost layer of the hair shaft; Medulla, a part of the optic lobe of arthropods; Medulla (lichenology), a layer of the internal structure of a lichen; Pith, or medulla, a tissue in the stems of vascular plants
The hair matrix, or simply matrix, produces the actual hair shaft as well as the inner and outer root sheaths of hair. [1] References This page was last edited ...