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Integumentary System
Skin system
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Organs making up the Integumentary System
- (1) Skin
- (2) Derivatives- hair, nails, glands, and nerve endings
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Structure of Skin
- (1) Epidermis- outer layer made of epithelium
- (2) Inner thicker dermis- made of connective tissue, overlies the subcutaneous layer
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Functions of the Skin
- (1) Regulation of body temperature
- (2) Protection
- (3) Sensation
- (4) Excretion
- (5) Immunity
- (6) Blood reservoir
- (7) Synthesis of vitamin D
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Epidermis
composed: stratified squamous and four principal types of cells: (1) keratinocytes (tonofilaments in cytoskeleton make keratin), (2) melanocytes (skin color), (3) Langerhans cells (immunity), and (4) Merkel cells (sensory touch)
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Layers of Skin (pic)
- Stratum Corneum (Superficial)
- Stratum Lucidum
- Stratum Granulosum
- Stratum Spinosum
- Stratum Basale (Deepest)
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Most Deepest Layer of the Epidermis
Stratum Basale (stratum germinativum)
- attached to the underlying dermis
- single row of stem cells- undergoes continuous cell division and produces all other layers
- basal cells divide:
- (1) one daughter cell is pushed into the cell layer above to being specialization into a mature keratinocyte
- (2) other daughter cell remains in the basal layer to produce new keratinocytes
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2nd Deepest Layer of Epidermis
Stratum Spinosum (prickly layer)
- several layers of keratinocytes unified by desmosomes
- contain thick bundles of intermediate filaments made of pre-keratin
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3rd Deepest Layer of Epidermis
Strantum Granulosum (granular layer)
- 4-6 cell layers
- keratinocyte appearance changes- flatten, nuclei and organelles begin to disintegrate form granules; (1) keratohyaline granules- help to form keratin in upper layers (2) lamellar granules- water barrier
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4th Deepest Layer of Epidermis
Stratum Lucidum (clear layer)
- 2-3 rows of clear, flat, dead keratinocytes
- tonofilaments
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Most Superficial Layer of Epidermis
Stratum Corneum (horny layer)
- 20-30 layers of dead cells
- 3/4 epidermal thickness
- glycolipid- waterproofs layer
- protection, water loss
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Dermis
- bellow of epidermis
- strong flexible connective tissue
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