PNB 2264 Lecture Notes - Lecture 4: Proteoglycan, Stratum Lucidum, Desquamation
16 Aug 2018
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Major role is protection so what is the tissue type: the type that provides the greatest protection. Thermoregulation: lose or gain heat, sweat. Production of 7-dehydrocholesterol (uv light: precursor to calcitriol (vitamin d) Epidermis (outer dermis: variable width, 0. 1mm to 1mm, largest human organ, each square inch contails ~650 sweat glands, ~20 blood vessels, ~1000 nerve endings, and ~60,000 melanocytes, five distinct layers. Avascular: no blood vessels, will not bleed with damage. Keratinocytes: 95% of all cells, contains keratin sensory cells. Basale (basal layer) stem cells spinosum (spiny layer) spiny shaped cells. Granulosum (granulated layer) granules lucidum (clear layer) clear, only found in palms and souls of feet corneum (hard layer) hard, tough, presence of desmosomes between cells. Deepest layer: between one and three cells thick (in hairless skin its thicker, stem cells, melanocytes, basal keratinocytes, site of cell division, 6-8 weeks to reach corneum. Stratum spinosum squamous epithelium lamellar bodies, lipid filled last site of mitosis keratinization begins here.
