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The Integumentary System
Objectives
• Describe the main structural features of the skin.
• Explain the mechanisms that produce hair and nails.
• Describe how skin responds to injury.
The integumentary system or integument is the largest system of the body.
- 16% of body weight
- 1.5 to 2 square meters in area
The integument is made up of 2 parts:
1. the cutaneous membrane, or skin,
2. the accessory structures
The cutaneous membrane is made up of 2 parts:
1. the outer epidermis or superficial epithelium (epithelial tissues) and
2. the inner dermis, composed of connective tissues
The accessory structures include hair, nails, and multicellular exocrine glands. These
structures generally originate in the dermis and extend through the epidermis to the skin’s
surface
Below the dermis is a subcutaneous layer of loose connective tissue, also known as the
superficial fascia or hypodermis (where hypodermic injections are administered). This is
not officially a component of the integument
The functions of skin and its subcutaneous layer include:
1. Protection against, abrasion, fluid loss and infection
2. Excretion of salts, water, and organic wastes by glands
3. Maintenance of body temperature by insulation (heating) and sweat
evaporation (cooling)
4. Synthesis of vitamin
5. Storage of lipids
6. Detection of touch, pressure, pain and temperature
The Epidermis
The most abundant cells in the epidermis are the keratinocytes (so called because they
contain large amounts of the protein keratin).
Most of the body is covered by thin skin, which has only 4 layers of keratinocytes in the
epidermis.
The palms of the hands and soles of the feet are covered with thick skin, which has 5
layers of keratinocytes in its epidermis.
