Physiology Topics
The skin and its accessory structures make up the intergumentary system. The functions of the skin are: regulation of body temperature, protection, sensation, excretion, blood reservoir and metabolism.
Body temperature is regulated by the skin in two ways. First sudoriferous glands secrete sweat, which cools the skin surface as it evaporates. Second the blood vessels in the skin will dilate or contract, bringing blood from other organs to be cooled off at the surface of the skin.
Protection provided by the skin is physical, chemical and biological. Keratin provides a water resistance. Lipids, lipid-soluble substances (including vitamins) and gases will more easily penetrate the skin than water or water-soluble substances. The pigment melanin protects somewhat against UV radiation. Biological protection is provided by langerhans cells in the epidermis and lymphocytes and phagocytes from vasculature. Although protective chemical secretion of the human skin have not been studied in detail, other animals like the frog are known to secrete antibiotic substances. The human skin is acidic, which prevents microbial growth and colonization.
Cutaneous sensations are mediated by specialized cells and nerve terminals as well as free nerve endings in the skin.
Excretion is not a major function of the skin, but it does occur. Especially when sweating profusely, significant amounts of ions may be excreted.
The skin carries 8-10% of the total blood flow in a resting adult, serving as a blood reservoir.
The skin will metabolize some drugs, for example: cortisone is converted to hydrocortisone. An inactive form of vitamin D (vitamin D3) is from in the skin from cholesterol by the action of UV light:
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other UV organs cholesterol → 7-dehydrocholesterol → vitamin D3 → vitamin D |
Continue to "Skin Layers" or take a quiz: [Q1] [Q2].
Need more practice? Answer the review questions below.
1- List the functions of the skin
2- How does skin regulate body temperature?
3- How permeable is the skin?
4- How is the skin protected against UV light?
5- How is the skin protected from infection?
6- How are cutaneous sensations mediated by the skin?
7- What is the excretory role of skin?
8- How is skin a blood reservoir?
9- What are the metabolic functions of skin?