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Integumentary system
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• Organization– Skin
• Epidermis• Dermis
– Accessory Structures• Hair & Hair follicles• Exocrine glands• Arrector pili• Sensory Receptors
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• Layers beneath the skin – Subcutaneous layer – Deep fascia
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• Functions of the Skin– Protection– Water-resistance– Temperature regulation– Vitamin D synthesis– Sensations– Immunity – Social signaling
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– Stratum Germinativum• Stem cells • Melanocytes• Merkel cells
The Epidermis
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– S. Spinosum• “Pre-keratinocytes”• Melanocytes• Langerhans cells
The Epidermis
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– S. Granulosum – S. Lucida
• Keratinocytes in both layers
The Epidermis
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– S. Corneum• Dead keratinocytes
The Epidermis
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Skin cell-eating mite
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The Dermis
• Reticular layer– Dense irregular CT– Provides strength
and elasticity
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The Dermis
• Papillary layer– Areolar CT– Contains cap’s and
sensory neurons for epidermis
– Arranged as dermal papillae
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• Perform secretory functions
• Perform transport functions
• Maintain physical integrity
• Ciliated epithelia move materials across their surface
Specializations of epithelium
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The Polarity of Epithelial Cells
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• Cells attach via cell adhesion molecules (CAM)
• Cells attach at specialized cell junctions– Tight junctions– Desmosomes– Gap junctions
Maintaining the integrity of epithelium
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Intercellular connections
Animation: check tutorials
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• Basal lamina attaches to underlying surface– Lamina lucida– Lamina densa
• Germinative cells replace short-lived epithelial cells
Structure of typical epithelium
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• Number of cell layers– Simple– Stratified
• Shape of apical surface cells– Squamous– Cuboidal– Columnar
Classification of epithelia
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Squamous Epithelia
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Cuboidal Epithelia
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Cuboidal Epithelia
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Transitional Epithelium
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Columnar Epithelia
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Columnar Epithelia
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Columnar Epithelia
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Pigmentation
• Melanin
• Carotene
• Hemoglobin
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Epidermal Derivatives
• Hair Follicles and Hair
• Skin Glands
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Hair
• Function– Protection– Touch Sensation
• Structure– Root– Shaft– Bulb
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Hair
• Hair Follicle– Sheath of epithelial
cells– Surrounds root– Merges with bulb
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Hair
• Associated structures– Dermal papilla– Sebaceous glands– Arrector pili
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Hair
• Growth Cycle– 2-5 yrs: growth
stage– 2 yrs: resting stage
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Skin Glands
• Sebaceous glands– secrete sebum– help to protect hair
and skin
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Skin Glands
• Merocrine (eccrine) sweat glands– BT control– excretion– protection
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Skin Glands
• Apocrine sweat glands– Secrete pheromones?
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Skin Glands
• Mammary glands
• Ceruminous glands
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Skin Sensory Receptors
• Free nerve endings
• Pacinian corpuscles
• Meissner’s corpuslces
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Lines of Cleavage
•