HTHSCI 1H06 Lecture Notes - Lecture 3: Connective Tissue, Loose Connective Tissue, Integument
9 Nov 2018
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Document Summary
Blood reservoir: dermis carries 8-10% of total blood volume, blood travels from skin to where it is needed. Chemical: oily secretions (sebum) secreted by sebaceous glands contain defensins and low ph sweat help retard the growth of microbes, melanin protects stem cells from damaging uv rays. Physical: continuity (no breaks, designated to withstand abrasion (thickness and keratin), several layers of epidermal cells. Biological: intraepidermal macrophages provide immune surveillance and help activate other immune cells. Cutaneous secretions: conveys external sensations to the spinal cord, pain, temperature, touch, pressure. Excretion and absorption: waste products such as ammonia and urea are excreted with sweat, a source of insensible h2o loss (breathing, sweating, absorbs lipids, gases, and organic solvents, only oils can penetrate keratin layer. Properties of epidermis: lacks blood vessels, receives nutrients via di usion, balance between cell production and cell loss (apoptosis; sloughing, entire process takes 4-6 weeks (7-10 days in psoriasis)
