1. The Integumentary System
Skin, Hair, Glands, Nails

2. the skin is the largest organ
it serves as a protective covering
it helps regulate body temp
it prevents water loss
it houses sensory receptors
it excretes wastes

3. Integumentary System Three layers Skin Epidermis 2. Dermis
3. Hypodermis (Subcutaneous layer)
Adipose
Accessory Structures
Hair - Nails -sebaceous glands
sweat glands (4 types)

4. The skin is composed of: the dermis (deep) and the epidermis (superficial)
Beneath the dermis is a layer composed of adipose and loose connective tissue called the Hypodermis (subcutaneous layer)

6. Epidermis composed of stratified squamous
lacks blood vessels – no vascularization
prevents water loss by secreting protein, keratin
keratinization of cells takes about 2 weeks

7. Epidermis (cont)
Contains cells called melanocytes that produce melanin (absorbs light energy & protects deeper cells); melanin gives skin its color

8. Skin Color all people have similar #s of melanocytes
diff. in skin color result from diffs in the amount of melanin that melanocytes produce and the distribution and size of the melanin granules
Albinism-inability to produce melanin

10. Dermis Is made up of two layers
Top layer (papillary layer) composed of areolar or loose connective tissue
Bottom layer (reticular layer) composed of dense connective tissue
Well vascularized & innervated
Also contains accessory structures such as; hair follicles, sebaceous glands, and sweat glands

11. Hair Composed of epidermal cells that have keratinized and died
Hair color is determined by the type and amount of pigment the melanocytes produce
arrector pili muscle - surrounds hair follicle & contracts when a person is cold or frightened (causes goose bumps) WHY?

12. Sebaceous Glands
a gland located around the hair follicle which secretes its contents when contracted by the arrector pili
secrete an oily mixture of fat and cellular debris called sebum which keeps the hair and skin soft, pliable, and waterproof
This is why hair get oily when not washed

14. Nails
Composed of dead stratified squamous epithelial cells which are extremely keratinized
Nail production occurs at the nail root which is underneath the skin and proximal to the visible nail.
Nails are basically clear and appear pink over skin because of underlying blood vessels

16. Sweat Glands (Exocrine Glands)
Eccrine Glands
respond to elevated body temp. due to heat or exercise
Cool by allowing water to be evaporated from skin lowering temp.
Common on forehead, neck, and back

17. Sweat Glands (Exocrine Glands)
release fluids thru pores
Gland located in dermis but release fluid through tube onto the top of the epidermis
sweat = water + salts and wastes. One salt is urea a key component in urine.

18. Sweat glands (cont.) 2. Apocrine glands
active when a person is emotionally upset, frightened, or in pain
found under the armpits and in the groin
Sweat is food for bacteria which increases the bad smell.

19. Sweat Glands (cont) 3. Other - ceruminous glands - secrete ear wax
- mammary glands - secrete milk

21. Regulation of Body Temperature
Regulation is important b/c heat affects the rate of metabolic reactions
when temp rises above the set point, dermal blood vessels dilate (get larger) and glands secrete sweat
when temp drops below the set point, dermal blood vessels constrict (get smaller) and glands become inactive
WHAT TYPE OF FEEDBACK?

22. Healing of Wounds
Skin injuries trigger inflammation; blood vessels dilate and become more permeable, forcing fluids to leave the blood vessels and enter the damaged tissues
WHAT TYPE OF FEEDBACK?
Dilated blood vessels supply the damaged cells with more oxygen and nutrients; this speeds healing.
More platelets are supplied to clot blood
More white blood cells needed to fight infection

23. Page 170-1