The integumentary system consists of the skin, hair, nails and related glands (sweat and sebaceous glands). It acts as a barrier to protect the body from the outside world. It also functions to retain body fluids, protect against disease, eliminate waste products, and regulate body temperature.

1- The Skin

The skin consists of

• Outer epithelial layer called epidermis.

• Formed of stratified squamous keratinized epithelium

• Inner connective tissue layer called dermis.

  • Formed of connective tissue having collagen & elastic fibers

  • It contains blood vessels, lymphatics, nerves, hair follicles & sweat glands.

• Deep layer called subcutaneous tissue.

Skin appendages

1-The nails: Are keratinized plates on the dorsal surface of the tips of fingers and toes.

2-Hairs ▪ Hairs are present over the whole surface of the body except lips, palms, soles, sides of fingers & toes, parts of external genital organs. 3-Sebaceous glands ▪ Open into the hair follicles and secrete oily materials. 4-Sweat glands ▪ They are long spiral glands which open on the surface of the skin. ▪ They are present over the surface of the body except lips, nail beds and parts of external genital organs.

Functions of the skin

1-Protection • Protection against mechanical, thermal and chemical damage, protection against water loss, ultraviolet rays and microorganisms. 2-Sensation It contains sense receptors & sensory nerves. 3-Temperature regulation • It aids in heat loss and heat retention through the fat, blood vessels and sweat secretion. 4-Synthesis of vitamin D 5- Excretion of urea and uric acid

2-Fascia

• Fascia is a connective tissue that lies immediately deep to the skin.

• There are two types of fascia: A. Superficial fascia. B. Deep fascia.

A. Superficial fascia

• Found immediately deep to the skin. It is a mixture oflooseareolar&fattytissuethatunitetheskinto the underlying deep fascia.

Function

1. Facilitate the movement of the skin.

2. Gives passage to vessels & nerves of the skin

3. Control the temperature of the body as the fat is bad conductor of heat. 4. Gives the body its rounded appearance B. Deep fascia It is a strong, dense, white fibrous layer that lies deep to the superficial fascia. Function

4. It is thickened in the palms & soles to provide protective function.

5. It invests the underlying muscles assisting their action.

6. It is thickened at the regions of the wrist and ankle forming retinaculae holding the underlying tendons in position during action.

3-Body cavities and membranes A. Body Cavities: • Body cavities are spaces within the body that contain and protect the organs. • There are two principal body cavities: the posterior body cavity and the larger anterior body cavity. • The posterior body cavity contains the brain and the spinal cord. • The anterior cavity is formed of upper chest cavity contains the heart and lungs and a lower abdominopelvic cavity contains abdominal and pelvic organs.

B. Body Membranes Body membranes are composed of thin layers of tissue that cover, separate, and support visceral organs and line body cavities. They are 1- The Pleurae: covers the lungs. 2- The Pericardium: covers the heart. 3- The Peritoneum: covers the abdominal viscera.