BIOL 1410 Lecture Notes - Arrector Pili Muscle, Stratified Squamous Epithelium, Integumentary System
18 Dec 2013
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Stratified squamous epithelium from ectoderm: epidermis: top. Melanocytes (10%) produce pigment/melanin for uv light protection (sunburn, wrinkles/collagen damage, cancer/dna) We have same number of melanocytes but produce different amounts/shades of melanin. Flat dead cells too far from blood supply. 30 layers of flat dead cells filled with keratin (tough protein) Shed and replaced from below: dermis: lower. Hair follicles, sebaceous glands, arrector pili muscles. Epidermal derivatives: hair, dead cells, bulb is the expanded region at base of root, hair follicle surrounds root (outer ct sheath from dermis, inner epithelial sheath from epidermis) Hair matrix: single layer epithelial cells derived from basale cells, growth and color. Hair papilla: ct of dermis extends beneath matrix to nourish dividing cells. Root hair plexus: free nerve endings for touch. Arrector pili muscle: smooth muscle - goosebumps: nails, heavily keratinized, nail root, body, and free edge, skin exocrine glands. Sebaceous glands: secretes sebum/oil, opens onto follicle.
