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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 shaft, which is the hard filamentous part that extends above the skin surface. It is made of multi-layered keratinized (dead) flat cells whose rope-like filaments provide structure and strength to it. The protein called keratin makes up most of its volume. A cross section of the hair shaft may be divided roughly into three zones.
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.
Anagen is the active growth phase of hair follicles [17] during which the root of the hair is dividing rapidly, adding to the hair shaft. During this phase the hair grows about 1 cm every 28 days. A hair pulled out in this phase will typically have the root sheath attached to it which appears as a clear gel coating the first few mm of the hair ...
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
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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.