1. Integumentary System

2. Integumentary System Consists of the skin, hair and nails
Acts as a barrier to protect the body from the outside world

3. Skin One of body’s largest organs It’s able to repair itself
It has sensory receptors to monitor the external environment
It rids body of wastes
It has 2 layers:
Epidermis
Dermis

4. Epidermis The outer layer of skin
Made of sheets of flattened, scaly epithelial cells
Top layers made of mostly dead cells that are lost daily:
This is most exposed to dangers of the outside, so it gives a protective layer
Replaced by new cells from lower layers
Filled with protein called keratin:
Gives skin its rough, leathery texture and makes it waterproof

5. So Many Colors
Color of skin determined by a brown pigment called melanin
Made in the lower layers of the epidermis
Absorbs UV radiation
UV radiation can damage DNA in skin and lead to skin cancer
The amount produced depends on heredity and how much UV radiation you’re exposed to

6. Dermis The inner layer of the skin It contains: Living cells
Sensory neurons: monitor signals from the environment (heat/pressure)
Blood vessels: nourishment for living cells; helps regulate body temperature
Muscle fibers: contract & pull hair upright (“goose bumps”)
Glands: produce sweat to cool body; oil to soften skin
Fat cells below dermis: energy reserve; insulation; shock absorbing layer
Video: What Is Skin For?

7. Glands Exocrine glands: Release secretions through ducts.
Main exocrine glands:
Sweat glands: Release excess water, salts, urea through skin.
Cools body when sweat evaporates
Oil glands: secrete a fatty substance called sebum.
Many are on your face and scalp
If glands clog, acne can result

8. Nails Protect ends of fingers & toes
Form from roots at base and sides of nail
New cells in root form: nail grows longer
Nails made of keratin
Changes in shape, structure, and appearance can indicate disease in body

9. Hair Protects and insulates body
Produced in pits of dermis called hair follicles
Composed of dead, keratin filled cells that overlap like roof shingles
Oil glands prevent hair from drying out
Individual hairs grow for several years then fall out
Hair color result of melanin & heredity