Components of the Integumentary System
The integumentary system is the most extensive of the organ systems in the human body. It has a number of roles, including regulating body temperature, excretion, protecting internal structures, vitamin D production and keeping microorganisms out of the body, reports Body Guide. The system is also integral in recognizing external stimuli (heat and cold, for example). It is made up several diverse components.
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Epidermis
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The epidermis is the outer portion of the skin and covers an area approximately 18 square feet, according to Body Guide. It is one continuous structure, but is considered distinct from the mucous membranes. The outer cells of the epidermis are composed almost entirely of fibrous protein material called keratin, which provides strength and flexibility to the skin. Other cells in the epidermis include the pigment producing melanocytes and langerhans' cells that deal with foreign bodies such as microorganisms.
Dermis
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The dermis is the found immediately beneath the epidermis. The section on the integumentary system in the “Online Biology Book,” written by Michael J. Farabee, Ph.D., notes that the dermis is composed primarily of connective tissues (collagen, elastin and reticular fibers). It is broken into two main layers: the papillary and reticular layers. The papillary layer provides nourishment to the epidermal layer and contains sense receptors. The reticular layer contains much of the supportive connective tissue and is also home to sense receptors.
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Glands
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The integumentary system also hosts a number of glands. One of the more widely known type of glands are the sudoriferous glands or sweat glands. Eccrine glands are the sweat glands triggered by heat, while the apocrine glands are triggered by sexual activities and secrete pheromones. The sebaceous glands are more commonly known as oil glands. The secretions of sebaceous glands are called sebum and help to moisturize the skin, reports Body Guide. If these glands become blocked or infected, acne can occur.
Follicles and Hair
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Hair follicles, according to The Online Biology Book, are responsible for the production of the proteins from which hair is composed. The follicles are found primarily in the dermal layer. Hair grows up from the follicle through the dermal and epidermal layers. Hair is constructed in three layers. The innermost layer, called the cortex, contains the pigmentation that provides hair color. The middle layer contains keratin, the same fibrous material found in the epidermis. The outer layer or cuticle is composed of layered scales of hard keratin.
Nails
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Nails are located at the end of each of the fingers and toes. They are primarily composed of keratinized cells, reports the Body Guide. The nail grows out of the nail root, which is protected by skin. The hard cells of the nail proper are held in place by the nail bed. The overhanging portion of the nail that appears white is called the lunula.
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References
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