The Skin

The structure and functions of the skin are described in this chapter

The skin, the largest organ of the body, has a complex structure and performs many functions that are important in maintaining homeostasis in the body. Probably the most important of these functions is the control of body temperature. The skin also protects the body from physical damage and bacterial invasion. The skin has an array of sense organs which sense the external environment, and also cells which can make vitamin D in sunlight.

Objectives

After completing this section, you should know:

• the general structure of the skin
• the function of the keratin deposited in the epidermis
• the structure and function of keratin skin structures including calluses, scales, nails, claws, hoofs and horns
• that antlers are not made either of keratin or in the epidermis
• the structure of hairs
• the structure of the different types of feathers and the function of preening
• the general structure and function of sweat, scent, preen and mammary glands
• the basic functions of the skin in sensing stimuli, temperature control and production of vitamin D
• the mechanisms by which the skin regulates body temperature

Summary

• Skin consists of two layers: the thin epidermis and under it the thicker dermis. * The Epidermis is formed by the division of base cells that push those above them towards the surface where they die and are shed.
• Keratin, a protein, is deposited in the epidermal cells. It makes skin waterproof.
• Various skin structures formed in the epidermis are made of keratin. These include: claws, nails, hoofs, horn, hair and feathers.
• Various Exocrine Glands (with ducts) formed in the epidermis include sweat, sebaceous, and mammary glands.
• Melanin deposited in cells at the base of the epidermis protects deeper cells from the harmful effects of the sun.
• The Dermis is composed of loose connective tissue and is well supplied with blood. Beneath the dermis is insulating adipose tissue.
• Body Temperature is controlled by: sweat, hair erection, dilation and contraction of dermal capillaries and shivering.

Learning Activities

Library of Resources

Presentations and Blackboard quizzes can be accessed by students of Otago Polytechnic.