05_LectureOutline

05_LectureOutline - Introduction to the Integumentary...

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Introduction to the Integumentary System The integument is the largest system of the body 16% of body weight 1.5 to 2 m 2 in area The integument is made up of two parts Cutaneous membrane (skin) Accessory structures The cutaneous membrane has two components Outer epidermis Superficial epithelium (epithelial tissues) Inner dermis Connective tissues Accessory Structures Originate in the dermis Extend through the epidermis to skin surface Hair Nails Multicellular exocrine glands Connections Cardiovascular system Blood vessels in the dermis Nervous system Sensory receptors for pain, touch, and temperature Subcutaneous layer (superficial fascia or hypodermis ) Loose connective tissue Below the dermis Location of hypodermic injections Functions of Skin Protects underlying tissues and organs Excretes salts, water, and organic wastes (glands)
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Maintains body temperature (insulation and evaporation) Synthesizes vitamin D 3 Stores lipids Detects touch, pressure, pain, and temperature Epidermis Epidermis is Avascular stratified squamous epithelium Nutrients and oxygen diffuse from capillaries in the dermis Cells of the Epidermis Keratinocytes Contain large amounts of keratin The most abundant cells in the epidermis Thin Skin Covers most of the body Has four layers of keratinocytes Thick Skin Covers the palms of the hands and soles of the feet Has five layers of keratinocytes Structures of the Epidermis The five strata of keratinocytes in thick skin From basal lamina to free surface Stratum germinativum Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum Stratum Germinativum The “germinative layer” Has many germinative (stem) cells or basal cells Is attached to basal lamina by hemidesmosomes Forms a strong bond between epidermis and dermis Forms epidermal ridges ( e.g., fingerprints) Dermal papillae (tiny mounds) Increase the area of basal lamina Strengthen attachment between epidermis and dermis Specialized Cells of Stratum Germinativum Merkel cells Found in hairless skin
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Respond to touch (trigger nervous system) Melanocytes Contain the pigment melanin Scattered throughout stratum germinativum Stratum Spinosum The “spiny layer” Produced by division of stratum germinativum Eight to ten layers of keratinocytes bound by desmosomes Cells shrink until cytoskeletons stick out (spiny) Continue to divide, increasing thickness of epithelium Contain dendritic (Langerhans) cells , active in immune response Stratum Granulosum The “grainy layer” Stops dividing, starts producing Keratin : a tough, fibrous protein makes up hair and nails Keratohyalin : dense granules cross-link keratin fibers Cells of Stratum Granulosum
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05_LectureOutline - Introduction to the Integumentary...

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