anatomy - integumentary system.docx

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Health Sciences
Health Sciences 2300A/B
Jeff St.Pierre

HS 2300: Systemic and Functional Anatomy The Integumentary System (Skin) NOTE: largest system in the human body Skin – 3 Layers 1. Epidermis 2. Dermis 3. Hypodermis Epidermis • “At surface” • Houses epithelial cells • Protects from outside systems (e.g. toxins) • Avascular – no vessels – no blood supply (if you scratch the surface, it will not bleed) • Ability to regulate itself (hot and cold) • When skin is torn, it is quickly rejuvenated – can repair itself • Composed of keratinized stratified squamous epithelium • 4 types of cells a. Keratinocytes (tough, carry melanin granules)  Dominating cell – composes 90% of cells in epidermis  Need melanin b. Melanocytes (colour granules, UV protection)  Inside keratinocytes  Melanin is produced in melanocytes (bottom layer of epidermis)  Dark appearance  Melanin is released and taken up by keratinocytes  Umbrella on top of nucleus  Provides UV protection (to DNA within nucleus) c. Merkel cells (sensory)  Neurons in the basal layer  Sense touching d. Langerhans cell (macrophages)  Tidy up broken down material  Housekeeping cell • 5 layers (stratum) a. Basale (deep)  Basement – houses melanocytes  High replication  Farthest for risk b. Spinosum (spider)  Spider-like c. Granulosum (water proofing, last area of oxygenation)  Cells need oxygen and carbon dioxide removal – this is hard because there is no blood supply  Start to die and shape changes, becoming a water-proofing barrier d. Lucidum (thick skin, dead)  Unique to areas with thick skin (e.g. heels and palms) HS 2300: Systemic and Functional Anatomy The Integumentary System (Skin) e. Corneum (dead but horny – cornified – cells)  Not alive but act as a barrier – makes it difficult for toxins to get to live cells  These cells are lost over time and replaced by “new” cells • NOTE: cells grow through replication from the bottom up – push existing cells to surface (oldest cells are at the surface) – continuous cycle that takes 4-6 months Dermis • Below epidermis • Very strong • Composed of connective tissue* cells and fat • Nerve fibers • Blood vessels • Microvilli; increases surface area (so oxygen can move in) and movement of substances • 2 layers: 1. Papillary (20%)  Houses vessels and nerves 2. Reticular (80%)  Reticular fibres have integrity – make up the shape and form of organs  Lots of connective tissue (very dense)  Irregular (fibers in different regions)  Solid – makes up strength  Ink in tattoos is here (reticular layers hold the ink in position) – eventually these will stretch and not replace Hypodermis • “Subcutaneous layer” • Dominating tissue in this layer is fat – also includes connective tissue, muscular tissue, and vessels (nerves and smooth muscle) • Hypo = low or below (below the dermis) • Insulating layer – storage depot (store fat and utilize for energy) – must have it (basal resting levels) • Formed by areolar and adipose tissue • Adipose predominates • Allows movement of muscle tissue below • The site of subcutaneous fat (different between s
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