1. Integumentary System Turn to your neighbor…what is the integumentary system?

2. SkinGlands HairNails FUNCTION: Act as a protective barrier to the outside world.

3. Body Bucket  retains body fluids  protects against disease  eliminates waste products  regulates body temperature Basically, holds all your “stuff” from falling out or getting contaminated.

4. How skin protects… Serving as a barrier against infection and injury Helping to regulate body temperature Removing waste products from the body Providing protection against ultraviolet radiation from the sun Producing vitamin D

5. Three main layers Epidermis Dermis Hypodermis

6. Sensory receptors Perceives sensations such as:  Pressure  Heat  Cold  Pain All of which are then transmitted to the nervous system.

7. EPIDERMIS Outer most layer of skin Composed of many sheets of flattened, scaly epithelial cells Thin layer of skin made mostly of dead cells Undergoes rapid cell division New cells are produced pushing older cells to the surface of the skin  The older skin begins making keratin There are no blood vessels in the epidermis which is why a small scratch will not cause bleeding

8. Keratin Is a tough fibrous protein Forms basic structure for hair, nails and calluses Eventually, the keratin-producing cells die and form a tough, flexible waterproof covering on the surface of the skin

9. Melanin (a dark brown pigment) Skin pigment Both light skinned and dark skinned people have roughly the same number of melanocytes (cells that produce pigment) The difference in our skin color is caused by the amount of melanin the melanocytes produce and distribute.

10. Amount of Melanin Dependent on two factors  Heredity  Length of time skin is exposed to ultraviolet radiation Role – absorption of ultraviolet radiation

11. DERMIS Middle thick layer of the skin composed of living cells Contains: blood vessels, nerve endings, glands, sense organs, smooth muscles, and hair follicles Helps control body temperature

12. Body temperature On cold days, the blood vessels (arteries) narrow/constrict Decreases surface area in order to conserve body heat On hot days the blood vessels (arteries) widen/expand warming the skin and increasing heat loss

13. Goose Bumps Tiny muscle fibers attach to hair follicles contract and pull hair upright when you are cold or afraid producing what we call “goose bumps”

14. Dermis contains two major glands Sweat glands  Secretions are stimulated by nerve impulses that cause the production of sweat when the temperature of the body is raised  They help cool the body off Oil glands  Produce oily secretion known as sebum that spreads out along the surface of the skin and keeps the keratin rich epidermis flexible and waterproof

15. Hypodermis This layer is beneath the dermis A layer of fat and loose connective tissue that insulates the body and acts as an energy reserve.

16. What causes blisters and calluses? the rubbing of the separate skin layers the epidermis and the dermis separate tissue fluid may collect between the layers skin prone to this pressure will create an area of thicker epidermis causing a callus

17. Burns Severity ranges from minor to fatal First degree burns  Only the superficial epidermis is affected  Painful but no blistering  Causes death of epidermal cells Second degree burns  Deeper layers of the epidermis are charred  Inflammations, blisters and painful

18. …burns continued Third degree burns  The entire epidermis is charred or burned away, and the burn may extend into the dermis  Not usually painful at first if the receptors in the dermis have been destroyed Extensive third degree burns  Loss of skin  Potentially life threatening because the natural barrier has been destroyed exposing tissue that is extremely susceptible to infection and dehydration

19. Hair Produced by cells at the base of the structures called hair follicles Hair follicles – tube like pockets of epidermal cells that extend into the dermis Individual hairs are actually large columns of dead cells that have been filled with keratin Hair gets color from melanin Protects and insulates the body

20. Nails Grow from rapidly divided cells known as the nail matrix or nail root Nail matrix is located near the tips of the fingers and toes During cell division, the cells fill with keratin and produce a tough, strong platelike nail that covers and protects the tips of the fingers and toes The pinkish color comes from the blood vessels in the nail bed Nails grow at a rate of 0.5 to 1.2 mm per day  Finger nails grow faster than toe nails

21. Diagram of the skin

22. Fun Facts Human body’s largest organ Integumentary derived from a Latin word meaning “to cover” The outer layer of dead skin cells is shed or washed away once every 14 to 28 days