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ID: 134539 • Letter: L
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• Sweat Glands - These glands produce moisture (sweat) which is secreted through tiny ducts to the surface of the skin (stratum corneum). The moisture serves as a cooling agent by making the surface of the skin moist. This moisture then evaporates and lowers the temperature of the skin.
A sweat gland is an elongated tubular structure that originates in the subcutaneous tissue beneath the dermis and extends up to the surface of the epidermis, where it ends at either a pore or a hair follicle.
At its secretory base, the gland is coiled and bunched, but its emerging duct straightens as it reaches toward the surface. A sweat gland is one of two types, eccrine or apocrine.
Eccrine sweat glands, of which there are a greater number than apocrine glands in the body, terminate in a pore. Therefore, eccrine glands are predominantly responsible for sweat secretion and cooling the body. They are found everywhere on the body except the rim of the lips and most of the penis. There may be as many as 2,000,000 to 5,000,000 eccrine glands in the body, with the greatest accumulation on the palms.
Apocrine sweat glands open into and feed hair follicles explicitly. They are typically larger than eccrine glands and are more developed in women. They are found in greatest number in the pubic region and in the armpit.
When an apocrine gland secretes sweat, some of its cells disintegrate. The product of this disintegration contributes to sweat, which, depending on the amount and type of bacteria it produces, carries an odor that is characteristic of perspiration.
Sebaceous Glands
Sebaceous oil-secreting glands are found in all types of skin, all over the body, and usually with a follicle. These glands, which resemble tree branches, are made up of a tube and one or two small sacs that are actually groups of smaller pockets called alveoli. They occur alongside the hair follicle as tiny teardrop appendages.
Sebaceous glands excrete oil that is produced when cells in the alveoli die and break apart. Their function is to lubricate hair and to facilitate sweating in the follicle. They do, however, occur in thin, hairless skin, like that of the inside or the mouth, where they aid in the regeneration of cells.
Epidermis
The epidermis, the outermost layer of skin, is thin but complex. Melanin, which is responsible for skin pigmentation, is found throughout the epidermis. The epidermis also "keratinizes" to produce nails, hair, sweat, and to regenerate. It is the foremost initiator of cell death and regeneration, the final boundary between body and environment. It is useful, however, to itemize the epidermis layer and its progressive keratinization from its innermost sublayer to its outermost, because cell growth naturally follows this pattern.
Keratinization, the maturation and migration of skin cells, begins in the innermost layer of the epidermis, the stratum germinativum. These cells, called keratinocytes, accumulate and move outward toward the next epidermis layer, the stratum Espinosa, where they become dense.
Dermis
The second, larger layer of skin is called the dermis. Its main roles are to regulate temperature and to supply the epidermis with nutrient-saturated blood. The dermis is made up of fibroblasts, which produce collagen connective tissues and which lend elasticity and support to the skin.
It is the seat of hair follicles, nerve endings, and pressure receptors. Furthermore, the dermis defends the body against infectious invaders that can pass through the thin epidermis, the first defense against disease.
Subcutaneous tissue
The subcutaneous tissue (also hypodermis and subcutis) is not part of the skin, and lies below the dermis of the cutis. Its purpose is to attach the skin to underlying bone and muscles well as supplying it with blood vessels and nerves. It consists of loose connective tissue, adipose tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (subcutaneous tissue contains 50% of body fat). Fat serves as padding and insulation for the body.
Fat layer
Below the dermis lies a layer of fat that helps insulate the body from heat and cold, provides protective padding, and serves as an energy storage area. The fat is contained in living cells, called fat cells, held together by fibrous tissue. The fat layer varies in thickness, from a fraction of an inch on the eyelids to several inches on the abdomen and buttocks in some people.
Hair - Hair serves a protective role in the skin. On most locations of the body, hair offers a protective covering, which regenerates on a regular basis. In some places, hair serves as a filter (such as in the nose and ears), a moisture and heat retention mechanism (such as the armpits and genital region), and in the middle ear it serves as a mechanism for regulating balance. Each hair follicle (in the hairy parts of the skin) is attached to a muscle, the arrector pili
• Sensory Nerves - These are the nerves that innervate the epidermis. These nerves are the subject of evaluation when examining a skin biopsy after it has been immunostained. The sensory nerves in the epidermis serve to sense and transmit heat, pain, and other noxious sensations. When these nerves are not functioning properly they can produce sensations such as numbness, pins-and-needles, pain, tingling, or burning.
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