Sponge: Set up Cornell Notes on pg. 51 Topic: 6.4 Accessory Structures of the skin

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

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

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

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

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

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

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

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

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

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

Extreme curvature Bluish Horizontal Furrows

Skin Glands • Sebaceous Glands • Sweat Glands

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

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

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

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

Sponge: Set up Cornell Notes on pg. 51 Topic: 6.4 Accessory Structures of the skin