Skin and Body Membranes Anatomy and Physiology Chapter 4

Function of Skin and Membranes Line or cover body surfaces Protect body surfaces Lubricate body surfaces

Classification of Body Membranes Epithelial Cutaneous Membranes Mucous Membranes Serous Membranes Connective Tissue Synovial Membranes

Cutaneous Membrane = SKIN What is it’s job? Outermost protective boundary Where is it found? Superficial epidermis A dry membrane (exposed to air) What is it made of? Keratinized stratified squamous epithelium Underlying dermis is mostly dense connective tissue

Mucous Membranes What is it’s job? Lines all body cavities that open to the exterior body surface Often adapted for absorption or secretion Where is it found? Surface epithelium What is it made of? Type depends on site Underlying loose connective tissue (lamina propria)

Specific serous membranes What is it’s job? Lines open body cavities that are closed to the exterior of the body Where is it found?&What is it made of? Surface simple squamous epithelium Underlying areolar connective tissue Serous layers separated by serous fluid Specific serous membranes Peritoneum: abdominal cavity Pleura: around the lungs Pericardium: around the heart

Connective Tissue Membrane What is it’s job? Provide a smooth surface and secrete a lubricating fluid Where is it found? Lines fibrous capsules surrounding joints Line bursae and tendon sheaths What is it made of? Synovial membranes Soft areolar CT No epithelial cells

Integumentary System Skin (cutaneous membrane) Skin derivatives Sweat glands Oil glands Hairs Nails

Protects deeper tissues from: Skin Functions to: Aid in heat regulation Aid in excretion of urea and uric acid Synthesize vitamin D Protects deeper tissues from: Mechanical damage Chemical damage Bacterial damage Thermal damage Ultraviolet radiation Desiccation

Skin Structure Epidermis Dermis Hypodermis Stratified squamous epithelium Often keratinized (hardened by keratin) Dermis Dense connective tissue Hypodermis Not part of the skin Anchors skin to underlying organs Composed mostly of adipose tissue

Layers of Epidermis Stratum Corneum Stratum Lucidum Stratum Granulosum Stratum Basale (Stratum Germinativum) Cells undergoing mitosis Lies next to dermis Stratum Spinosum Stratum Granulosum Stratum Lucidum Occurs only in thick skin (like the palm) Flatter, full of keratin Stratum Corneum Shingle-like dead cells ¾ epidermal thickness 20-30 cell layers thick

Melanin Pigment produced by melanocytes Color is yellow to brown to black Melanocytes are mostly in the stratum basale Amount of melanin produced depends upon genetics and exposure to sunlight NPR Story: http://www.npr.org/templates/story/story.php?storyId=100057939

Dermis: 2 Layers… Animal “hide” Projections called dermal papillae Pain receptors Capillary loops Papillary layer Blood vessels Glands Nerve receptors Deepest skin layer Reticular layer

Skin Structure

Normal Skin Color Determinants Melanin Yellow, brown or black pigments Carotene Orange-yellow pigment from some vegetables Hemoglobin Red coloring from blood cells in dermis capillaries Oxygen content determines the extent of red coloring

Appendages of the Skin Sebaceous Glands Sweat Produce oil Lubricant for skin Kills bacteria Most with ducts that empty into hair follicles Glands are activated at puberty Sweat Widely distributed in skin Two types Eccrine - Open via duct to pore on skin surface Apocrine - Ducts empty into hair follicles