Ronald A. Bergman, Ph.D., Adel K. Afifi, M.D., Paul M. Heidger,
Peer Review Status: Externally Peer Reviewed
Hair Arrector pili muscle
This illustration is part of a drawing from the work of Johannes Sobotta.*
Longitudinal sections through the hairs of the human scalp show their free ends (shafts) and the roots embedded in the deep inpocketings or follicles consisting of both an epithelial and a connective tissue sheath.
Also note the relationship between the hair follicle, sebaceous gland, and arrector pili muscle. The smooth muscle bundles forming the arrector pili muscle are obliquely placed in relation to the epidermis. Contraction of the muscle results in the erection of the hair shaft (and follicle), producing depressions in the skin (orange peel appearance) commonly known as gooseflesh, and compresses sebaceous glands aiding in the emptying of the glands into the hair follicle, thereby oiling the hair shaft. The secretion of the sebaceous gland is known as sebum, which is a complex mixture of triglycerides, waxes, squalene, and cholesterol and its esters as well as remnants of degenerating and dead cells.
Eccrine (merocrine) sweat glands are located in the fatty, superficial fascia (hypodermis) or in the deep dermis. Their ducts extend up and through the surface of the epidermis.
Eccrine sweat glands secrete water, ammonia, sodium chloride, urea, and uric acid. Sweat glands aid in temperature regulation of the body, react by secreting in stressful situations, and act as an excretory organ by eliminating metabolic waste products.
*Sobotta was a twentieth-century German anatomist.
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