Organization Skin Epidermis Dermis Accessory Structures Hair Hair

• Organization – Skin • Epidermis • Dermis – Accessory Structures • Hair & Hair follicles • Exocrine glands • Arrector pili • Sensory Receptors

• Layers beneath the skin – Subcutaneous layer – Deep fascia ____________

• Functions of the Skin – Protection – Water-resistance – Temperature regulation – Vitamin D synthesis – Sensations – Immunity – Social signaling

ØThe Epidermis – Stratum Germinativum • Stem cells • Melanocytes • Merkel cells

ØThe Epidermis – S. Spinosum • “Prekeratinocytes” • Melanocytes • Langerhans cells

ØThe Epidermis – S. Granulosum – S. Lucida • Keratinocytes in both layers

ØThe Epidermis – S. Corneum • Dead keratinocytes

Skin cell-eating mite

ØThe Dermis

ØThe Dermis • Reticular layer – Dense irregular CT – Provides strength and elasticity

ØThe Dermis • Papillary layer – Areolar CT – Contains cap’s and sensory neurons for epidermis – Arranged as dermal papillae

ØPigmentation • Melanin • Carotene • Hemoglobin

Ø Epidermal Derivatives • Hair Follicles and Hair • Skin Glands

ØHair • Function – Protection – Touch Sensation • Structure – Root – Shaft – Bulb

ØHair • Hair Follicle – Sheath of epithelial cells – Surrounds root – Merges with bulb

ØHair • Associated structures – Dermal papilla – Sebaceous glands – Arrector pili

ØHair • Growth Cycle – 2 -5 yrs: growth stage – 2 yrs: resting stage

ØSkin Glands • Sebaceous glands – secrete sebum – help to protect hair and skin

ØSkin Glands • Merocrine (eccrine) sweat glands – BT control – excretion – protection

ØSkin Glands • Apocrine sweat glands – Secrete pheromones?

ØSkin Glands • Mammary glands • Ceruminous glands

ØSkin Sensory Receptors • Free nerve endings • Pacinian corpuscles • Meissner’s corpuslces

Lines of Cleavage •