Physiology Of Skin

FUNCTION OF SKIN Skin ( Cutis ) is the outer covering of the body , consisting of the dermis & epidermis , resting upon the subcutaneous tissue

Dermis—connective tissue substrate

1- SENSATION  The

largest single organ of sensation & the importance of sensory innervation especially the modalities of touch ( mechanoreceptors ) , pain (nociceptors ) , hot & cold ( thermoreceptors ) are obvious .

2- PROTECTION  

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From its environment by keratin which is a mechanically strong fibrous protein . By folds of the dermal – epidermal interface which prevents the 2 components from sheared apart . Shearing forces are also dissipated by movement of skin over the loosely woven superficial fascia . Dermis enables folds of skin to be lifted with out tearing. Minor injuries are rapidly repaired by virtue of the regenerative power . Protection from microbial invasion although some are found in sweat glands & hair follicles .

3-WATER PROOFING  

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In dry environment , it is a mean of preventing fluid loss . Impermeability of keratin to water is maintained by the thickened lipid wall but some chemicals are lipid soluble & can penetrate . The secretion of sebaceous glands over the skin & the outer ear by the modified sweat glands or ceruminous glands secrete water repellent wax .

4- WATER BALANCE  Because

of activity of sweat glands → insensible & largely unmeasurable loss ( 500 cm³ – 900 cm³ / day ) in a temperate climate when no sweating is apparent . Salt loss becomes significant in athletes training & heavy manual workers

5- HEAT REGULATION  The

surface temperature of the skin regulates the rate at which heat is lost from the body .  Reflex erection of hairs by arrector pili muscles occurs in response to cold .  The use of hair in defensive or offensive responses as a reflex is obvious in fear , anger & excitement .

6- PROTECTION AGAINST RADIATION  Against

ultraviolet radiation & is genetically controlled .  Vitamin D is produced in skin during ultraviolet radiation .