Skin - The Integumentary System Skin Accessory Organs...

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The Integumentary System: Skin & Accessory Organs Largest organ system largest surface area Skin – 2 layers o Epidermis (not very thick) – stratified squamous epithelium o Dermis (thicker) – deeper connective tissue layer – 2 layers - 1. Loose connective tissue (most superficial) 2. Dense irregular connective tissue (deeper layer) Hypodermis (not part of the skin) – below the dermis Cutaneous Glands o Sudoriferous (sweat) glands o Sebaceous (oil) glands Hair & Hair Follicles Nails Characteristics of Epithelia Tissue (Review from Chapter 5) Cellularity close packed cells o Primarily the keratinocytes are bound together by protein filaments that hold them into tight junctions and have desmosomes that anchor them together Polarity way to retard water intake and also prevent water loss o Because we have an apical and basal side Not innervated By themselves are not nervous tissue o Have to have nervous tissue from the dermis o Have tactile cells (Merkel cells) o Free nerve endings are in the dermis Avascular rely on diffusion to get nutrients o Wont see any vasculature within the epidermis o When you scrape yourself and bleed you scraped off the epidermis and now down to the dermal layer Epidermis is not that thick compared to the dermis o Dermal capillaries -> all nutrients have to diffuse from these to the deepest layers of the dermis o Only get diffusion in the first couple layers Regenerative
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The Integumentary System: Physiological Functions 1. Protection/Barrier – 3 types- Chemical, mechanical/physical, biological Barrier to water o Prevents the body from absorbing or losing excess water Barrier to UV rays o Blocks cancer causing radiation from reaching deeper tissue o The chemical melanin moves into a keratinocyte Migrates specifically on the sunny side of the nucleus Creates a chemical barrier from UV rays mutating the nucleus which would then change (possibly) the generation of that cell o One way of getting skin cancer Barrier to many potential harmful chemicals o However, permeable to several drugs and poisons Resists and recovers from trauma better than other organs do Epidermis cells packed with the tough protein keratin 2. Regulation of Body Temperature Cutaneous nerve endings called thermoreceptors o Monitor the body surface temperature 3. Cutaneous Sensation – what makes up the structures of the epidermis and structures made up in the dermis all here The skin is our most extensive organ Variety of nerve endings that react to: o Heat, cold, touch, texture, pressure, vibration and tissue injury 4. Metabolic Functions Vitamin D Synthesis o The skin carries out the first step in the synthesis of vitamin D 5. Blood Reservoir 6. Excretion In addition to secreting sweat to cool the body o Sudoriferous (sweat) glands of the skin also excrete waste products out of the body.
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