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Skin and Body Membranes Chapter 4
2 Types of Body Membranes A. Epithelial and B. Connective Epithelial Membrane=Skin, Mucous Membrane, Serous Membrane Connective Membranes=Synovial (areolar connective tissue) that has no Epithelial cells
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Epithelial Membranes Skin (Integument) Wet Exterior Openings
Interior Linings
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A. Cutaneous/Integument/Skin
Waterproof-Stretchable-Washable Self-Repairs: Cuts, Rips, and Burns Electrical Insulation Includes: Sweat and Oil Glands, Hairs, and Nails
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Functions of the Skin Mechanical Damage Physical Barrier
Chemical Damage Acids and Bases Bacterial Damage Unbroken Surface, “Acid Mantle” Ultraviolet Radiation Melanin protects from Sun Thermal Damage Heat/Cold/Pain Receptors Desiccation Waterproofing Surfaces Heat Loss/Retention Skin Capillary Access Urea and Uric Acid Excretion Perspiration Vitamin D Sunlight
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Skin Structure Epidermis Hypodermis Dermis Stratified Squamous
Keratinizing (hardening) Dermis Dense Connective Contains Blood, Sweat, and Oil Glands Hypodermis A.K.A Subcuaneous tissue Adipose Tissue Anchor Skin (E&D) to underlying organs
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3 Layers-Actual Picture
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Epidermis-5 Strata (Layers)
*****OUTSIDE THE BODY***** EPIDERMI S Corneum Lucidum Granulosum Spinosum Basale *****DERMIS*****
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Why can we shave (face/legs) and not bleed?
The epidermis is AVASCULAR, meaning it has no blood supply of its own. Most cells produce keratin (tough, fibrous protein) Basale (alive with spino- and granulo-) absorbs nutrients, the top 2 (lucid- and corne-) are non-living
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Then why do you bleed when you shave?
Because you cut too deeply and get into the DERMIS
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The 5 Strata Layers Corneum:20-30 cells thick
Lucidum: dead, clear cells found only on hands/feet Granulosum: still living cells Spinosum:living cells Basale: absorb nutrients from the dermis to keep them alive, and “float” up to form the above 4 layers
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New EPIdermis every 25-45 days
Suntans/burns occur in the Basale Melanin (colored pigment) Basale cells phagocytize (eat) the melanin Melanin shields DNA from UV rays
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Papillary and Reticular
The Dermis Divided into 2 Layers- Papillary and Reticular
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Papillary Layer Upper projections called papillae containing pain and touch receptors (known as Meissner’s corpuscles)
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Reticular Layer Contains blood vessels, sweat and oil glands and deep pressure receptors (Pacinian corpusles) Many phagocytes to attack bacteria that has passed through Epi- Collagen fibers and blood vessels
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