BIOL 243 Lecture 8: Integumentary System
26 Sep 2016
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Document Summary
Consists of 2 distinct regions: epidermis= superficial region. Hypodermis (superficial fascia: subcutaneous layer deep to skin, not part of skin but shares some functions, mostly adipose tissue that absorbs shock and insulates, anchors skin to underlying structures- mostly muscles. Four or five distinct layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin, stratum corneum. Four cell types: keratinocytes, melanocytes, langerhans cells (dendritic cells, merkel cells (tactile cells) Keratinocytes: produce fibrous protein keratin, most cells of epidermis, tightly connected by desmosome. Melanocytes: 10-25% of cells in deepest epidermis, produce pigment melanin. Protect apical surface of keratinocyte nucleus from uv damage. Dendritic (langerhans) cells: macrophages- key activators of immune system. Tactile (merkel) cells: sensory touch response. Single row of stem cells: actively mitotic, produces two daughter cells. One cell journeys from basal layer to surface. One cell remains in stratum basal as stem cell. Cells contain web like system of intermediate prekeratin filaments attached to desmosomes.
