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Classification of Membranes
• Epithelial– Cutaneous
• Skin• Stratified squamous
– Mucous (mucosa)• Lines cavities• Simple columnar
• Serous– One layer– Simple squamous– Serous fluid
• Parietal & Visceral– Lines body cavities– Around organs– Pleura & Pericardium– Simple squamous
Functions of the Skin
• Protection– Against disease– Insulates & cushions– UV protection– Chemical protection
• Defense– 1st line of defense
• Prevention of Dehydration– Keratin– Keeps H2O in & out
Functions of the Skin
• Maintenance of Body Temp.– Heat loss – sweat– Heat retention – blood flow
• Excretion of Wastes– Salts– Urea– H2O
• Reception of Stimuli– Touch, pressure, pain, cold, heat
• Vitamin D Synthesis– Cholesterol molecules Vitamin D (sunlight)
Layers of the Skin - integumentary
• Epidermis– Strata
• Stratum basale– Closest to dermis– Undergoes mitosis– Nutrients from diffusion
• Stratum spinosum– Flattened cells w/ spines
• Stratum granulosum– Granules w/ keratin
• Stratum corneum– “horny”– 20-30 cell layers– Soles. Palms, fingertips-stratum lucidum
Cell Types
• Keratinocytes–Make keratin
• Melanocytes–Make melanin– Secretes melanin – basale layer
• Langerhans cell–Macrophages-eat foreign substances
Skin Color – amount and kind
• Pigments– Melanin
• Reddish brown, or black– Carotenes
• yellow– Hemoglobin
• rosy
• Emotional– Redness (sympathetic)
• Embarrassment • Anger• Fear• Allergies
Dermis – “hide” leather
• Thick connective tissue layer beneath stratum basale.– Collagen– Elastin
• Papillary layer– Upper, uneven– Receptors (pain, touch)– Dermal papillae
• Fingers-fingerprints• Soles-footprints
Dermis cont…
• Reticular layer– Deepest– Blood vessels– Sweat and oil glands– Blood supply when restricted• Degeneration• Ulceration – bed sore
Appendages of the Skin• Glands– Sebaceous glands
• Oil• Sebum: lubricant, bacteria killing• Whiteheads (blocked oil gland) blackhead acne• Seborrhea – excess oil
– Sweat glands – 500 ml a day (25 million)• Eccrine
– Sweat– Clear– 99% water– Salts, urea, lactic acid,– pH 4-6
• Apocrine– Axillary & genital areas– Fatty acids, proteins, sweat (yellowish)– Empty into hair follicles
Appendages of the Skin cont..
• Nails– Modified epidermal cells– Keratin
• Hair– 100,000 hairs scalp– Follicle
• Keratinized cells• Arrector Pili (goose bumps)– smooth muscles -Hairs
erect-increase blood flow to skin
– Cuticle• Keep hairs separate
Infections and Allergies1000 different conditions
• Fungi– Athletes foot fungus– Ringworm
• Bacterial– Boils and carbuncles
• Staphylococcus into hair follicles• Oil glands
– Impetigo• Viruses– Herpes “cold sores”– Warts
Skin in Stress• Wound Repair– Wound– Inflammatory reaction
• Blood flow– Edema
• swelling– Clots
• Stop bleeding– WBC’s
• Fight bacteria– Pus
• Dead blood cells• Dead bacteria
– Scabs
Skin in Stress cont…• Burns– Thermal
• Heat• Chemical – electrical - UV
– First degree• Epidermis “red”• Heal 2-3 days
– Second degree• Epidermis & dermis• Blisters
– Third degree• Skin blackens• Skin grafts
– Risk of death• Fluid loss , imbalance of electrolytes• Kidney failure• Replace proteins , infection
Skin Cancer• Basal Cell Carcinoma
– Most common– Alters stratum basale cells
• Uncontrolled mitosis can’t form keratin
• Squamous Cell Carcinoma– Stratum spinosum– Scaly reddish papulae– Spreads to lymph nodes
• Malignant Melanoma – (5%)– Brown black patches– Lymph & blood vessels– ABCD rule moles– Asymmetrical, border, color, diameter 76mm