The Structure Of Skin

Let us consider how the skin is structured to better understand how this tissue performs some of its vital functions. Consider the cross-section of the skin sketched in Figure 1. This illustration shows the readily distinguishable layers of the skin, from the outside of the skin inward, are (i) the «10-|im-thin, fully differentiated, devitalized outer epidermal layer called the stratum corneum; (ii) the «100-|im-thin, live, cellular epidermis; and (ill) the «1000-|im-thin (1-mm-thin) dermis. Note that all the thicknesses specified here are representative only, for the actual thickness of each stratum varies severalfold from place to place on the body. Dispersed throughout the skin, varying in number and size

Sketch Skin

pilorum 1 muscle

Dermal vasculature vasoulalure


Slralum comeum (10-15^)^

Dermis [aoo-soDt3jifhJJ

Subcutaneous i farty tissue Subcutaneous vasculature-

Hair sha«


Setaceous \ 3la"d gland

SrraLum corneum

Living epidermis



Figure 1 Sketch of the skin.

depending on body site, are several glands and appendages. These include (i) hair follicles and their associated sebaceous glands (pilosebaceous glands), (ii) eccrine sweat glands, (ii'O apocrine sweat glands, and (iv) nails of the fingers and toes. Each appendage has its unique population densities and body distributions. The appendages also exhibit characteristic structural differences from one location to another on the body.

A highly complex network of arteries, arterioles, and capillaries penetrates the dermis from below and extends up to the surface of, but not actually into, the epidermis. A matching venous system siphons the blood and returns it to the central circulation. Blood flow through the vasculature is linked to the production and movement of lymph through a complementary dermal lymphatic system. The dermis is laced with tactile, thermal, and pain sensors.

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