BIO 167 Lecture Notes - Lecture 5: Lymph Node, Glycolipid, Lysosome
26 Apr 2021
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Document Summary
Skin: largest organ of the body, composed of 2 distinct regions, epidermis superficial layer, epithelial tissue, dermis lies under epidermis, vascularized, nutrients diffuse through to reach epidermis. Layers of epidermis: thick skin: found in areas subject to abrasion, palm, fingertips, soles of feet, five layers, thin skin. Stratum basale (basal layer: also known as stratum germinativum, deepest epidermal layer, single layer of cuboid shaped stem cells. Actively mitotic: produces two daughter cells, one cell migrates from basal layer to surface, takes 25-45 days, dies as it moves toward surface, one cell remains as a stem cell, melanocytes compose 10-25% of this layer. Stratum spinosum (prickly layer: prickle cells , 8-10 layers thick, keratinocytes appear to have spines. Contain tension-resisting bundles of pre-keratin filaments: due to cell shrinkage but junctional complexes (desmosomes) hold tight. Melanin granules and dendritic cells are most abundant in this layer.
