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

–Stratum Germinativum Stem cells Melanocytes Merkel cells  The Epidermis

– S. Spinosum “Pre- keratinocytes” Melanocytes Langerhans cells  The Epidermis

– S. Granulosum – S. Lucida Keratinocytes in both layers  The Epidermis

– S. Corneum Dead keratinocytes  The Epidermis

Skin cell-eating mite

 The Dermis

Reticular layer – Dense irregular CT – Provides strength and elasticity

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

 Pigmentation Melanin Carotene Hemoglobin

 Epidermal Derivatives Hair Follicles and Hair Skin Glands

 Hair Function – Protection – Touch Sensation Structure – Root – Shaft – Bulb

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

 Hair Associated structures – Dermal papilla – Sebaceous glands – Arrector pili

 Hair Growth Cycle – 2-5 yrs: growth stage – 2 yrs: resting stage

 Skin Glands Sebaceous glands – secrete sebum – help to protect hair and skin

 Skin Glands Merocrine (eccrine) sweat glands – BT control – excretion – protection

 Skin Glands Apocrine sweat glands – Secrete pheromones?

 Skin Glands Mammary glands Ceruminous glands

 Skin Sensory Receptors Free nerve endings Pacinian corpuscles Meissner’s corpuslces

Lines of Cleavage