3.3 – Physiology (Function) of the Integumentary System
3.3 – Physiology (Function) of the Integumentary System
The skin and accessory structures perform a variety of essential functions, such as protecting the body from invasion by microorganisms, chemicals, and other environmental factors; preventing dehydration; acting as a sensory organ; modulating body temperature and electrolyte balance; and synthesizing vitamin D. The underlying hypodermis has important roles in storing fats, forming a “cushion” over underlying structures, and providing insulation from cold temperatures.
Protection
The skin protects the body from wind, water, and UV sunlight. It acts as a protective barrier against water loss and it also is the first line of defense against abrasive activity such as grit, microbes, or harmful chemicals. Sweat excreted from sweat glands deters microbes from over-colonizing the skin surface by generating dermicidin, which has antibiotic properties.
Sensory Function
The skin acts as a sense organ because the epidermis, dermis, and the hypodermis contain specialized sensory nerve structures that detect touch, surface temperature, and pain. These receptors are more concentrated on the tips of the fingers, which are most sensitive to touch, especially the Meissner corpuscle, which responds to light touch, and the Pacinian corpuscle, which responds to vibration. Merkel cells, seen scattered in the stratum basale, are also touch receptors. In addition to these specialized receptors, there are sensory nerves connected to each hair follicle, pain and temperature receptors scattered throughout the skin, and motor nerves innervate the arrector pili muscles and glands. This rich innervation helps us sense our environment and react accordingly.
Thermoregulation
The integumentary system helps regulate body temperature through its tight association with the sympathetic nervous system. The sympathetic nervous system is continuously monitoring body temperature and initiating appropriate motor responses.
When the body becomes warm, sweat glands, accessory structures to the skin, secrete water, salt, and other substances to cool the body.
- Even when the body does not appear to be noticeably sweating, approximately 500 mL of sweat are secreted a day.
If the body becomes excessively warm due to high temperatures, vigorous activity, or a combination of the two, sweat glands will be stimulated by the sympathetic nervous system to produce large amounts of sweat.
- When the sweat evaporates from the skin surface, the body is cooled as body heat is dissipated.
- In addition to sweating, arterioles in the dermis dilate so that excess heat carried by the blood can dissipate through the skin and into the surrounding environment.
- This accounts for the skin redness that many people experience when exercising.
When body temperatures drop, the arterioles constrict to minimize heat loss, particularly in the ends of the digits and tip of the nose.
- This reduced circulation can result in the skin taking on a whitish hue.
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