Thermoregulation and Skin Functions - Anatomy and Physiology
- What makes the skin a barrier against water loss?
- Keratinized cells and lipids in the stratum corneum and stratum granulosum block water from escaping.
- What role does the skin play in vitamin D production?
- UVB light converts 7-dehydrocholesterol in the skin to cholecalciferol (vitamin D3), which the liver and kidneys then activate.
- Which mechanism accounts for most heat loss from a resting person in a cool room?
- Radiation of infrared energy from the skin to cooler surroundings.
- What are the four physical mechanisms by which the skin loses heat?
- Radiation, conduction, convection, and evaporation.
- How does the hypodermis contribute to temperature regulation?
- Its adipose tissue insulates the body and reduces heat loss to the surroundings.
- How do dermal blood vessels help release excess heat?
- They dilate, bringing more warm blood close to the skin surface so heat can leave the body.
- What is the acid mantle of the skin?
- The slightly acidic film on the skin surface (pH around 5) that inhibits the growth of many microbes.
- A breeze cools dry skin faster than still air at the same temperature. Which heat-loss mechanism is increased?
- Convection, because moving air carries warmed air away from the skin surface.
- How does melanin protect the skin?
- It absorbs ultraviolet radiation, protecting the DNA of keratinocytes from UV damage.
- Air temperature is 40 °C, above skin temperature. Which heat-loss mechanism can still remove heat from the body?
- Evaporation of sweat. Radiation, conduction and convection add heat when the surroundings are warmer than the skin.
- Which sweat glands are the main source of sweat for heat loss?
- Eccrine (merocrine) sweat glands, found over most of the body surface.