Anatomy and Physiology Resource Site

4.3 - Functions of the Integumentary System

The skin is the largest organ in the human body by mass, and is important in homeostasis and the protection of deeper tissues.

Homeostatic functions of the skin

Temperature regulation

When body temperature is too high, eccrine sweat glands secrete watery sweat, which then evaporates, cooling the skin. Blood capillaries in the skin dilate to allow warmer blood from deeper tissues to release its heat through the skin.
When body temperature is too low, blood capillaries in the skin constrict to prevent warm blood from deeper tissues from losing its heat through the surface of the skin.

Water regulation

Glycolipids and keratin in the upper layers of skin prevent the skin from drying out and prevent water loss from the body as a whole.

Waste regulation

Nitrogenous wastes (urea and uric acid) are excreted by the sweat glands

Vitamin D synthesis

Vitamin D is manufactured by the skin, and is needed to absorb Calcium in the digestive system.

Protective functions of the skin

Physical protection

Several skin structures are responsible for physical protection:

Keratin toughens cells, helping to prevent tearing
Fat cells in the subcutaneous layer cushion deeper structures
Pressure receptors help prevent the organism from damaging itself
Temperature and pain receptors help prevent thermal damage from hot or cold surfaces or substances

Chemical protection

Keratinized cells are resistant to damage from acids and bases and pain receptors warn the organism of the presence of harmful chemicals on the skin.

Sunlight protection

Melanin in keratinized cells near the surface of the skin helps block ultraviolet radiation from damaging delicate underlying structures.

Pathogen protection

When undamaged, the integument is a continuous surface preventing the entry of bacteria into the body. Acidic sebum produced by eccrine sweat glands helps to inhibit bacterial growth. If pathogens enter the dermis, resident phagocytes engulf and destroy foreign substances before they can invade deeper tissues.