1. Sponge: Set up Cornell Notes on pg. 51 Topic: 6.4 Accessory Structures of the skin Essential Question: 2.1 Atoms, Ions, and Molecules 6.4 Accessory Structures of the Skin

2. Accessory Structures of the Skin Hair Follicles and Hair Nails Glands. Pg. 51

3. Accessory Structures of the Skin 3 Originate from hair follicles As long as accessory structures remain intact, severely burned or injured dermis can regenerate

4. 4 Hair Follicles Composed of living epidermal cells Lose 20-100 hairs a day Hair present on all skin surfaces except palms/soles/lips/nipples/parts of reproductive organs epidermal cells divide and grow Pushed toward surface Die Hair=dead epidermal cells

5. 5 When hair is not replaced= baldness Genes determine hair color by directing the type and amount of pigment that epidermal melanocytes produce

6. 6 Hair’s Functions? Warmth Protection Touch Sense Eyelashes and Eyebrows? Protect eyes from dirt, sweat, rain etc Hair on head? Protection from sun Other hair on body Touch sense warmth

7. 7 Human Hair vs Chimp Hair Appearances can be deceiving! We have the same amount of hair per square inch as a chimpanzee Our hair is just shorter, thinner, and lighter

8. 8 Lanugo (La-new-go) and Hypertrichosis (Hyper-trick-o-sis) Babies are covered with lanugo while in the womb, some babies are born with a thin layer still visible In a very rare disorder called hypertrichosis- the lanugo remains and grows long

9. 9 Our hair persisted in places where our individual scents cling “Parasite-reduction hypothesis” Fur entraps fleas, lice and ticks Which spread diseases Lose the fur….loose the parasites

10. 10 Nails protective coverings on fingers and toes specialized epidermal cells Mirrors health Bluish= circulation problem Horizontal furrows= period of serious illness/malnutrition Certain disorders may lead to extreme curvature of the nails Ex: Cystic Fibrosis

11. 11 Extreme curvature Bluish Horizontal Furrows

12. 12 Skin Glands 1.Sebaceous Glands 2.Sweat Glands

13. 13 Sebaceous Glands usually associated with hair follicles Produces fatty material called sebum which is secreted into follicles through ducts (OIL!!!) Keep skin and hair soft and waterproof Acne results from excess sebum secretion

14. 14 Sweat Glands widespread in skin Consists of tiny tube that originates as a ball shaped coil in the deeper dermis Lined with sweat secreting epithelial cells

15. 15 Most numerous= eccrine glands Respond primarily to temperature change Also in palms/soles and release sweat when emotionally distressed Sweat= mostly water, some salt, some waste Apocrine glands- develop a scent as they are metabolized by skin bacteria Become active @ puberty Also active during sexual arousal in groin/nipples

16. 16 Clinical Application Acne Vulgaris most common skin disorder sebum and epithelial cells clog glands produces whitheads and blackheads (comedones) anaerobic bacteria trigger inflamation (pimple) largely hormonally induced androgens stimulate sebum prodiction treatments include antibiotics, topical creams, birth control pills