Skin_S - Skin(Integument) Consistsofthreemajorregions 1.

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Skin (Integument) Consists of three major regions 1. Epidermis—superficial region 2. Dermis—middle region 3. Hypodermis (superficial fascia)— deepest region Subcutaneous layer deep to skin (not  technically part of skin) Mostly adipose tissue
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Figure 5.1 Epidermis Hair shaft Dermis Reticular layer Papillary layer Hypodermis (superficial fascia) Dermal papillae Pore Subpapillary vascular plexus Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Nervous structures Sensory nerve fiber Pacinian corpuscle Hair follicle receptor (root hair plexus) Cutaneous vascular plexus Adipose tissue
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Epidermis Keratinized stratified squamous  epithelium  Cells of epidermis Keratinocytes—produce fibrous  protein keratin Melanocytes 10–25% of cells in lower  epidermis Produce pigment melanin
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Figure 5.2a Dermis Stratum corneum Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Stratum granulosum 3 to 5 layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. Stratum spinosum Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and epidermal dendritic cells. (a)
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Layers  of  the  Epidermis:  Stratum  Basale  (Basal  Layer)                  Stratum  Spinosum Deepest epidermal  layer firmly attached  to the dermis Single row of stem  cells Journey from basal  layer to surface Takes 25–45 days  Cells contain a  weblike system of  intermediate  prekeratin filaments  attached to  desmosomes Abundant melanin  granules and dendritic  cells 
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         Stratum Granulosum Thin; three to five cell  layers in which the  cells flatten Lucidum (Clear Layer) In thick skin Thin, transparent 
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This note was uploaded on 10/13/2010 for the course BIOL 2404 taught by Professor Royster during the Spring '10 term at Lone Star College System.

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Skin_S - Skin(Integument) Consistsofthreemajorregions 1.

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