Integumentary system

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 –

Perform secretory functions Perform transport functions Maintain physical integrity Ciliated epithelia move materials across their surface Specializations of epithelium

The Polarity of Epithelial Cells

Cells attach via cell adhesion molecules (CAM) Cells attach at specialized cell junctions –Tight junctions –Desmosomes –Gap junctions Maintaining the integrity of epithelium

Intercellular connections Animation: check tutorials

Basal lamina attaches to underlying surface –Lamina lucida –Lamina densa Germinative cells replace short-lived epithelial cells Structure of typical epithelium

Number of cell layers –Simple –Stratified Shape of apical surface cells –Squamous –Cuboidal –Columnar Classification of epithelia

Squamous Epithelia

Cuboidal Epithelia

Transitional Epithelium

Columnar Epithelia

 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