BIO 211 Lecture Notes - Lecture 4: Stratum Spinosum, Toxicodendron Radicans, Calcifediol

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16 Jan 2019
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Unit d: integument: integument in general, general information, body"s largest organ, composed of all 4 tissue types. Nervous tissue for sensation of touch, pressure, temperature, and pain: protects internal body structures, ~8% of body weight, thickness depends on body location. Palms and bottom of feet are thickest: function, protection. Injury and trauma: harmful chemicals, toxins, microbes, temperature extremes, protects deeper tissue from sunburn (solar radiation) Protection: immune: epidermal dendritic cells in stratum spinosum, attack cancer cells. Protection: prevention of water loss/gain: epidermis is water resistant, prevents absorption, water lost by sweat and transpiration, fluids penetrate through epidermis and evaporate in air, dehydration a danger with severe burns, water escapes without skin barrier, metabolic regulation. Vitamin d3 (cholecalciferol) metabolism: synthesized from steroid by keratinocytes, occurs upon uv exposure (10-15 mins) D3 released into blood liver: converted to intermediate (calcidiol) Transported to kidney and converted to calcitriol: active form of vitamin d, regulating blood calcium and phosphate.