1. Unit 3: Integumentary System A&P Chapter 5

2. Learning Goals Copy at TOP of page 43
1) Describe the 3 layers of the skin including the location and what structures are found in each.
2) Explain the 5 functions of the skin including how each relates to homeostasis.

3. 1. Integumentary System The Integumentary system includes:
Skin – largest organ of the body
Accessory Organs:
Hair
Nails
Serves to protect the viscera (internal organs) and regulate temperature

4. 11. Structure of the Skin
The skin is composed of 3 layers from superficial to deep:

5. 1. Epidermis Outermost layer of skin
Stratum Corneum – hard outermost layer of epidermis
Produces a protein called keratin
Keratinization causes hardening of dead skin cells, making skin waterproof.
Stratum Basale – produces new cells of epidermis
Contains Langerhans cells (for immunity) and melanocytes (make pigment to give skin color)

6. 2. Dermis Thick layer of connective tissue containing:
Dermal papillae – ridges that cause fingerprints and provide gripping surface
Collagen & elastic fibers – stretching & movement
Blood vessels
Sensory Nerves
Sebaceous Glands
Hair Follicles

7. 3. Hypodermis (Subcutaneous Layer)
Deepest layer of skin
Composed of loose connective tissue and adipose tissue (fat)
Helps to store energy, insulate body, and provides protective padding

8. IV. Five Functions of the Skin
1. Protection
Physical barrier to disease, dirt, and UV radiation
Bacteria and other invaders are prevented entry by the top dead layer of skin and the acidic, oily secretion from sebaceous glands (sebum).

9. 2. Regulates Water Loss
Keratinization of the dead skin outer layer also prevents water from entering or leaving the skin, even when immersed in water.
Skin works with the urinary system to sweat off some excess water.

10. 3. Produces Vitamin D
Melanocytes produce melanin to protect against harmful UV radiation from the sun and also to produce Vitamin D
Vitamin D helps regulate the uptake of calcium by the digestive system.
Calcium is needed for strong bones.

11. 4. Gathers Sensory Information
Sensory receptors are linked to the nervous system
Receptors specialize in sensing
Touch
Pressure
Pain
Temperature (hot & cold)
Many receptors in hands

13. 5. Regulates Body Temperature
When the body is too hot, the skin will help to release heat to cool the body temperature back to 98.6°:
Sweat
Dilation of dermal blood vessels

14. When the body is too cold, the skin will help to raise body temperature back to 98.6° by generating heat:
Shivering (muscle contraction)
Goosebumps (contraction of arector pili muscles attached to hair follicles) cause hair to trap heat
Constriction of dermal blood vessels

15. Bad things happen when body temp. is not constant:
1. Hypothermia -Lower body temp. than normal interferes with the body’s normal functions and eventually ends in death

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2. Hyperthermia—Higher body temp. than normal results in dehydration (from excess sweating) and heat stroke.