skin

Integumentary System

Components

Skin

Appendages

Nails

Follicles

Hair

Sudoriferous Glands (sweat glands)

Sebaceous Glands (oil glands)

Functions

Protection from abrasion

Protection from desiccation

Protection from infection

Regulation of body temperature

direction and redirection of blood flow to the surface

sweating

Layers of the Skin

Epidermis (a stratified squamous epithelium)

Stratum basale: deepest layer of the epidermis; this layer is technically only one cell layer thick and is attached to the basement membrane, which separates the epidermis from the dermis. This area is constantly undergoing cell division to produce new epidermal cells.

Stratum spinosum: the next few layers of cells superficial to the S. basale; this layer is characterized by having "spine-like" projections protruding through adjacent cells and is an active area of cell division. Together, the S. basale and S. spinosum are referred to as the Stratum germinativum because of their mitotic activity

Stratum granulosum: several layers of non-dividing cells characterized histochemically by the presence of hyalokeratin (keratohyaline) and fine cytoplasmic granules

Stratum lucidum: this area may be only a couple of cell layers thick to many layers thick depending upon the amount of abrasion or "callousing" that occurs; it is thick on the ball of the foot, for example, but practically absent on the instep. The chemical eleiden (derived from hyalokeratin) is found in this layer.

Stratum corneum: outermost layer of the epidermis averaging 20 layers or more in thickness. Cells here are progressively more flattened as they near the surface. Keratin , derived from eleiden, is found here. This protein is largely responsible for the ability of the skin to protect from desiccation.

Dermis or Coreum (a dense irregular connective tissue)

Papillate dermis: the portion of the dermis that interdigitate with the epidermis
Reticulate dermis: the remainder of the dermis, deep to the Papillate dermis

Glands

Sudoriferous Gland (sweat gland): the body of this gland is located in the dermis; the gland consists of compound cuboidal epithelium; the secretion is simply called sweat or perspiration; these glands are merocrine, meaning that their secretion is fluid only.
Sebaceous Gland (oil gland): secretion is sebum; these glands are holocrine, meaning that their secretion contains entire cells; most, but not all, sebaceous glands secrete into hair follicles.