September 25 Lecture

September 25 Lecture - September 25, 2008 Integumentary...

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Unformatted text preview: September 25, 2008 Integumentary System Skin- Outermost layer: stratum corneum o Flattened (usually dead) cells o Contain a large amount of soft keratin; they have become karotinized o This layer is constantly being shed- Bottom of epidermis: stratum germinativium- Processes of cell shedding can be sped up via being exposed to intense light (i.e. sunburn)- Ells are replaced via stratum germinativium- Thickest skin found in the palms of the hand and soles of the feet o Thick skin is distinct; contains 5 layers (bottom up) 1. Status basal (germinativium) Single cell layer (stem cell, most active in mitosis) 2. Stratum spinosum 8-10 cell layers. Appear spiny or prickly (due to cytoskeleton with irregular spiny characteristic). Has some mitotic activity 3. Stratum granulosum Cells begin to die: lose nucleus and protein begins to be converted to keratin and keratohyalin leadings to keratinization. Cells have stopped dividing. 4. Statum lucidum Thin layer, translucent dead keratinized cells. Serves to protect underlying cells from effects of sunlight as well as UV (and sunburn) 5. Stratum corneum 20-30 cell layers, saturated with soft keratin. Undergoing constant shedding and replacement. Protects against physical, solar, and chemical activities, also protects against dehydration- Thin skin contains 4 layers and covers most of the body o Missing the layer of stratum lucidum o Stratum corneum is somewhat thinner than in thick skin o Some texts combine stratum spinosum and stratum basal referring to them as stratum germinativium (Both in mitotic division, not many differences)- In epidermis, melanocytes (in addition keratinized cells) can be found...
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September 25 Lecture - September 25, 2008 Integumentary...

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