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In humans, some of the more common skin appendages are hairs (sensation, heat loss, filter for breathing, protection), arrector pilli (smooth muscles that pull hairs straight), sebaceous glands (secrete sebum onto hair follicle, which oils the hair), sweat glands (can secrete sweat with strong odour or with a faint odour (merocrine or eccrine ...
Also, there are nontrichomatous epidermal cells that protrude from the surface, such as root hairs. A common type of trichome is a hair. Plant hairs may be unicellular or multicellular, and branched or unbranched. Multicellular hairs may have one or several layers of cells.
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. [1] The epidermis layer provides a barrier to infection from environmental pathogens [2] and regulates the amount of water released from the body into the atmosphere through transepidermal water loss.
The outer root sheath corresponds with the stratum mucosum (stratum germinativum and stratum spinosum) [1] of the epidermis, and resembles it in the rounded form and soft character of its cells; at the bottom of the hair follicle these cells become continuous with those of the root of the hair.
In the embryo, the epidermis, hair, ... Epidermal nevi, neoplasms, and cysts are skin lesions that develop from the epidermal layer of the skin. [8] [26]
The protein keratin stiffens epidermal tissue to form fingernails. Nails grow from a thin area called the nail matrix at an average of 1 mm per week. The lunula is the crescent-shape area at the base of the nail, lighter in color as it mixes with matrix cells. Only primates have nails. In other vertebrates, the keratinizing system at the ...
The structure, consisting of hair, hair follicles, arrector pili muscles, and sebaceous glands, is an epidermal invagination known as a pilosebaceous unit. [ 4 ] Sebaceous glands are also found in hairless areas ( glabrous skin ) of the eyelids , nose , penis , labia minora , the inner mucosal membrane of the cheek , and nipples . [ 4 ]
Pig skin especially shares similar epidermal and dermal thickness ratios to human skin: pig and human skin share similar hair follicle and blood vessel patterns; biochemically the dermal collagen and elastin content is similar in pig and human skin; and pig skin and human skin have similar physical responses to various growth factors. [1] [2]