Textbook Notes (367,758)
Canada (161,374)
BIOB34H3 (77)
Ted Petit (12)
Chapter 5

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Biological Sciences
Ted Petit

Chapter 5 Integumentary System • Epidermis - Keratinized stratified squamous epithelium 1. keratinocytes (90% of cells) a. produce fibrous protein keratin (as intermediate filaments of cytoskeleton) b. help provide protective properties of skin 2. melanocytes (8%) a. produce pigment melanin that protects from UV light b. have projections that extend between keratinocytes, keratinocytes phagocytize projections to take in melanin 3. Langerhans cells a. produced in red bone marrow b. important in immune response c. projections form a network in some layers 4. Merkel cells a. associated with nerve endings (Merkel discs) b. important in sense of touch - Thickness ranges from .1 mm – 2 mm - Layers of epidermis (strata, from deep → superficial) 1. Stratum basale a. one row of mainly cuboidal or columnar keratinocytes b. melanocytes and Merkel cells scattered among keratinocytes c. divide often, older cells push upward and become parts of other layers (accumulate more keratin) d. also known as stratum germinativum 2. Stratum spinosum a. 8 - 10 cells thick, more superficial keratinocytes are flatter b. some keratinocytes can still divide c. Langerhans cells and projections of melanocytes 3. Stratum granulosum a. 3 - 5 cells thick, flattened keratinocytes b. nuclei and organelles degenerate, lots of keratin (many cells dead) c. cells contain keratohyaline granules (bundles together keratin filaments) d. also lamellar granules (lots of lipids, forms waterproof barrier between this and superficial layers) 4. Stratum lucidum a. only in thicker skin (palms and soles) b. 3 - 5 cells thick, very flat, dead keratinocytes c. lots of keratin and keratohyaline 5. Stratum corneum a. 25 - 30 cells thick, very flat, dead keratinocytes b. lots of keratin, keratohyaline and lipids from lamellar granules c. waterproof barrier that protects from light, heat, chemicals and invaders d. constantly shed • Dermis - Connective tissue with other embedded structures 1. cells include fibroblasts, macrophages 2. contains blood vessels and nerves 3. glands and hair follicles are embedded - Regions of dermis 1. papillary region a. areolar CT with elastic fibers b. projects into epidermis as dermal papillae c. loops of capillaries d. touch receptors e. cause ridges in epidermis (fingerprints) 2. reti
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