1. The Integumentary System

2. The Skin The largest organ in the body – Covers the entire body Function: acts a a barrier against infection and injury, helps tregulate body temperature, removes wastes, provides protection against ultraviolet radiation from the sun

3. Contains many types of sensory receptors: pressure, heat, cold, and pain are transmitted to the nervous system from your skin Made up of two layers: – Epidermis – dermis

4. Epidermis The epidermis is the outer layer of your skin It is made up of two parts – Outer layer – made of dead cells, comes in contact w/environment – Inner layer – made of living cells

5. The inner layer undergoes rapid cell division Newer cells push older cells towards the surface, these cells then become flat and the organelles disintegrate. The cells produce keratin which is a tough fibrous protein, when these cells die they form a tough, flexible, waterproof barrier

6. Melanocytes are cells in the epidermis that make melanin Melanin is a dark pigment that protects your skin by absorbing harmful ultraviolet rays

7. Dermis The inner layer of the skin Contains: collagen fibers, blood vessels, nerve ending, glands, sensory receptors, smooth muscles, and hair follicles.

8. Two types of glands in the dermis: Sweat glands produce perspiration (sweat) – Cools you off (evaporation) Sebaceous glands produce sebum (oil) – Keeps skin flexible and waterproof

9. Skin Cancer Excessive exposure to ultraviolet radiation can produce skin cancer Skin cancer is an abnormal growth of cells

10. Hair and Nails Hair and nails are made of keratin – Horns, scales, feather and quills in other animals Hair covers almost every surface of the body – Protection from UV rays – Filters particles from entering body (nose,ears)

11. Hair is made by cells at the base of hair follicles, which are tube-like pockets of epidermal cells Nails grow from cells called nail roots Nails protect the tips of fingers and toes