WARM UP 12/4 1. Give 3 functions of sebaceous glands. 2. What is an autograft? 3. A chemical that gives skin its color. 4. What are four things found in sweat? 5. Why do we sweat? 6. What makes us more sensitive in some areas of our skin than others?

NOTES Ch 5 12/4 HAIR

Develops from the ectoderm at week 20 Fine hair - lanugo FOUND: everywhere on our body except palms and soles

FUNCTION 1. Protection: a. cold b. UV light c. dust,debris (eyelashes, brows, nasal hairs)

PARTS 1. FOLLICLE – tube hair lies in 2. MATRIX – cells at the base that form into hair 3. CUTICLE – outer layer of the hair, scaly, dead keratinized cells a. Straight hair – round b. Curly hair – flat (not as strong)

4. CORTEX – middle layer; contains melanin for color 5. MEDULLA – center of hair 6. ROOT – End of hair in follicle 7. ERECTOR PILI – smooth muscle that attaches to each hair; contraction causes goosebumps

8. HAIR BULB – enlarged base of hair 9. PAPILLAE – at base of hair; contains connective tissues and blood vessels to give hair nutrients *melanin added here

bULb Sebaceous gland Erector pili muscle papillae cuticle cortex medulla Hair follicle Germinal matrix root

HAIR GROWTH 1. Mitosis at the germinal matrix make hair cells 2. Cells move upward through follicle as new cells push them up 3. Supply from papillae become less and they die 4. Keratin is added to the cells 5. Hair cells pushed out of the epidermis and can be seen now.

CYCLES OF HAIR GROWTH 1. Anagen – growth phase 2. Telogen – resting stage Length of hair depends on length of growing phase 2-6 years grow Rest 3 months Fall out Average growth – ½ inch/month (5 “ year)

About 100,00 hairs on your head Lose a day, but are being replaced

AFFECTING HAIR GROWTH 1. Age 2. Diet 3. Health 4. Seasons 5. Genetics 6. Hormones