5. Integumentary System (1).pptx - Integumentary System The Skin and the Hypodermis \u2022 Skin\u2014our largest organ \u2013 Accounts for 7 of body weight \u2013

5. Integumentary System (1).pptx - Integumentary System The...

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Integumentary System
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The Skin and the Hypodermis Skin—our largest organ Accounts for 7% of body weight Varies in thickness from 1.5 to 4.4 m m Divided into two distinct layers Epidermis Dermis Hypodermis —lies deep to the dermis Composed of areolar and adipose tissues Not part of the integumentary system but shares some of skin’s properties
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Figure 5.1 Skin Structure Hair shaft Papillary dermis Reticular dermis Sensory nerve fiber with free nerve endings Lamellar corpuscle Hair follicle receptor (root hair plexus) Dermal papillae Subpapillary vascular plexus Sweat pore Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Dermal vascular plexus Adipose tissue Epidermis Dermis Subcutaneous tissue (hypodermis; not part of skin)) Nervous structures Appendages of skin
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Figure 5.2 Gross Structure of Skin and Underlying Tissues Deep fascia Muscle Hypodermis Dermis Epidermis
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The Skin and Hypodermis (1 of 2) Five important functions 1. Protection Cushions organs and protects from bumps, chemicals, water loss, and ultraviolet (U V) radiation 2. Body temperature regulation Capillary network and sweat glands regulate heat loss 3. Excretion Urea, salts, and water lost through sweat
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The Skin and Hypodermis (2 of 2) Functions 4. Production of vitamin D Epidermal cells use U V radiation to synthesize vitamin D 5. Sensory reception Contains sense organs associated with nerve endings
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Epidermis (1 of 3) Is composed of keratinized stratified squamous epithelium Contains four main cell types Keratinocytes Location—stratum spinosum; produce keratin, a fibrous protein Melanocytes Location—basal layer; manufacture and secrete pigment
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Epidermis (2 of 3) Contains four main cell types Tactile epithelial cells Location—basal layer; attached to sensory nerve endings Dendritic cells Location—stratum spinosum; part of immune system; macrophage-like
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Epidermis (3 of 3) Keratinocytes —most abundant cell type in epidermis Arise from deepest layer of epidermis Produce keratin , a tough fibrous protein Produce antibiotics and enzymes Are dead at skin’s surface
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Layers of the Epidermis (1 of 6) Stratum basale (stratum geminativum) Stratum spinosum Stratum granulosum Stratum lucidum (only in thick skin) Stratum corneum
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Figure 5.3a Epidermal Cells and Layers of the Epidermis Stratum corneum Stratum granulosum Stratum spinosum Stratum basale Dermis Desmosomes Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. One to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin.
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