ZOO 3713C Lecture Notes - Lecture 10: Epidermal Growth Factor, Stratum Basale, Neural Crest
Document Summary
Histogenesis various cell types develop in concert to form a tissue. Cytodifferentiation individual cells become increasingly specialized, finally reaching a terminal differentiated state. Ectoderm single layer simple cuboidal epithelium. Layers 4 weeks of gestation periderm: flattened cells involved in exchange between the basal layer and the amniotic fluid. Peridermal cells (slough off: apoptosis, gone by 21st week. Basal layer (stratum germinativum, stratum basale) stem cells of epidermis. Intermediate layer keratinocytes keratin = intermediate filaments. Stratum basale stem cells: growth stimulators e. g. epidermal growth factor (egf), fibroblast growth. Factor (fgf), insulin-like growth factor (igf), transforming growth factor a (tgfa) Stratum spinosum keratin produced in cytoplasm keratinocytes. Stratum granulosum post-mitotic cells keratohylin granules protein (histidine-rich and sulfur-rich) keratin aggregates. Melanocytes melanoblasts are migratory neural crest cells that invade the epidermis. Number of melanocytes is constant variation in the amount of melanin synthesized (from tyrosine via tyrosinase.
