The skin is one of the largest and heaviest organ of the body. In an average adult, the skin covers about 2 square meters (22 square feet), weights 4.5-5 kg (10-11 lb) and varies in thickness (1.5 to 4.0 mm) depending on what part of the body it covers.

The skin covers all of the exposed surface of the body and is continuous with the mucous membranes lining openings into the body surface, such as those of the digestive, respiratory and urogenital systems.

The skin consists of 2 layers,

- 1 - the outer epidermis, derived from the embryonic ectoderm and

- 2 - the inner dermis which develops from the mesoderm.

The appendages of the skin such as hair, nails, sebaceous glands and sweat glands develop from the embryonic epidermis.

Beneath the dermis is the hypodermis (=subcutaneous tissue = superficial fascia) which anchors the skin loosely to underlying tissues (mainly muscles). The hypodermis is NOT part of the skin

The skin and its appendages(hair, nails, sebaceous and sweat glands) make up a very complex set of organs that accomplishes several functions:

- 1 - Protection: barrier against the outside

- 2 - Protection against dehydration

- 3 - Body Temperature Regulation

- 4 - Cutaneous Sensation

- 5 - Metabolic Functions

- 6 - Blood Reservoir

- 7 - Excretion

Objective: - Identify the components of the Integumentary system and describe their structure and functions.