Anatomy and Physiology / Unit 3: The Integumentary System
3.4 Functions of the Skin
Notes
- Protection: chemical (acid mantle, melanin), physical (keratin barrier), biological (Langerhans cells and macrophages).
- Body temperature regulation: when warm, dermal vessels dilate (vasodilation) and sweat evaporates; when cold, vessels constrict (vasoconstriction) to conserve heat.
- Cutaneous sensation: receptors for touch, pressure, pain, temperature.
- Metabolic functions: UV light helps the skin make vitamin D3, needed to absorb calcium.
- Blood reservoir: the dermis holds up to about 5% of blood volume. Excretion: small amounts of salts, water and urea in sweat.
- Example: during exercise on a hot day, skin looks flushed because of vasodilation.
Practice
A person exercising in heat has flushed skin. This is caused by:
Dilated vessels bring warm blood near the surface so heat is lost.
Which vitamin is synthesized in the skin with exposure to ultraviolet light?
The skin converts a cholesterol derivative to vitamin D3 under UV light.
Why does the skin help prevent infection?
The skin uses physical, chemical and biological defenses.
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