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

Epithelial Membranes Skin (Integument) Wet Exterior Openings Interior Linings

A. Cutaneous/Integument/Skin Waterproof-Stretchable-Washable Self-Repairs: Cuts, Rips, and Burns Electrical Insulation Includes: Sweat and Oil Glands, Hairs, and Nails                         

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

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                                                                

3 Layers-Actual Picture

Epidermis-5 Strata (Layers) *****OUTSIDE THE BODY***** EPIDERMI S Corneum Lucidum Granulosum Spinosum Basale *****DERMIS*****

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

Then why do you bleed when you shave? Because you cut too deeply and get into the DERMIS

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

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

Papillary and Reticular The Dermis Divided into 2 Layers- Papillary and Reticular

Papillary Layer Upper projections called papillae containing pain and touch receptors (known as Meissner’s corpuscles)

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