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Anatomy 200 - Integumentary System

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David Begg

INTEGUMENTARY SYSTEM Components: - Skin (Cutaneous Membrane) o Epidermis (Epithelium) o Dermis (Connective Tissue) - Accessory Structures o Hair o Nails o Exocrine Glands Functions: - Physical and immunological protection - Thermoregulation - Sensation - Metabolic Functions o Vitamin D synthesis o Stores energy as subcutaneous fat Composition (all four tissue types): - Epithelium o Covers surface o Forms boundary - Connective tissue o Supports epithelium o Provides strength and resiliency - Muscle o Controls diameter of blood vessels o Controls position of hairs - Nerve o Controls smooth muscles o Sensation o Stimulates glands Skin - Largest organ system - Area of 2 square meters - 15% of body weight - 0.5mm to 4.0mm Layers of the Epidermis (from deep to superficial): - Dermis - Dermal papilla - Cutaneous Layer Gives Sexy Girth o Stratum germinativum (basal)  Give rise to new keratinocytes  Attached to basal lamina o Stratum spinosum “spiny layer”  Keratinocytes contain tonofilaments (attach to desmosomes)  Desmosomes attach keratinocytes together  Keratinocytes still capable of division o Stratum granulosum “granular layer”  Large number of keratin filaments  Keratohyalin forms matrix around filaments  Secrete lipids to fill spaces between cells (water-repellent sealant)  Keratinocytes die o Stratum lucidum “clear layer”  Found in thick skin of finger tips and soles of feet o Stratum corneum (corne – hard or hoof-like)  Multiple layers of dead cells  Cells shed and are replaced  Protects against abrasion and microbe invasion Epidermal Cells - Melanocytes (at the basal lamina) o 8% of epithelial cells o Produce melanin pigment o Long slender processes that insert between keratinocytes - Langerhans Cell o Bone marrow to Epidermis o Function in immune response - Merkel Cell o Found in basal layer o Function in touch sensation Skin Color - Due to: o Dermal blood supply o Variable quantities of three pigments  Melanin (brown/black)  Absorbs UV and prevents UV-induced DNA damage  Pheomelanin (red/yellow)  Carotene (yellow/orange) - Pale skin o Hemoglobin in dermal blood vessels o When lowered oxygenation of blood, hemoglobin darkens
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