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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.
Some skin secretions are associated with body hair. Skin secretions originate from glands that in dermal layer of the epidermis. Sweat, a physiological aid to body temperature regulation, is secreted by eccrine glands. Sebaceous glands secrete the skin lubricant sebum. Sebum is secreted onto the hair shaft and it prevents the hair from splitting.
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. The integumentary system includes skin, hair, scales, feathers, hooves, claws, and nails.
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 follicle is an organ found in mammalian skin. [1] It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between hormones, neuropeptides, and immune cells. [1]
The inner root sheath or internal root sheath of the hair follicle is located between the outer root sheath and the hair shaft. [1] It is made of three layers: Henle's layer, Huxley's layer, and the cuticle. [2] The inner root sheaf serves to protect growing hair. [3]
Huxley's layer is the second layer of the inner root sheath of the hair and consists of one or two layers of horny, flattened, nucleated cells. It lies between Henle's layer and the cuticle . [ 1 ]
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.