The Integumentary System PDF

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ANPS 020, Ellen Black...

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2/21 The Integumentary, Immune and Lymphatic System Describe the basic structure and functions of the skin - Structure: - Epidermis: keratinized stratified squamous epithelium resting on basement membrane, protective shield - Dermis: loose and dense irregular connective tissue, bulk of the skin - Hypodermis: loose CT and adipose tissue, anchors skin to muscle - Protection: mechanical trauma, invasion of pathogens, environmental hazards (UV radiation) - Sensation: sensory receptors - Functions: - Thermoregulation: maintenance of internal body temperature through negative feedback loops - Excretion: waste products (lactic acid, urea, metals) lost through sweat - Vitamin D synthesis: UV light reaction with modified cholesterol to produce cholecalciferol Describe in detail the layers of the epidermis and dermis - Cells of the epidermis: - Keratinocytes: production of keratin, desmosomes - Melanocytes: synthesize melanin - Dendritic (Langerhans) cell: phagocytose foreign substances; activate immune system - Merkel (tactile) cell: sensory receptor for touch, associated with nerve ending - Layers of the epidermis: - Stratum basale (basal layer)/ Stratum Germinativum - Deepest layer attached to dermis, closest to blood supply, youngest keratinocytes, single row of stem cells continually dividing, 10-25% of cells are melanocytes - Stratum spinosum (Prickly layer) - Several layers thick, system of intermediate filaments (pre-keratin) spanning cytosol and connecting to desmosomes, appear spiky under microscope, contains dendritic cells - Stratum granulosum (granular layer) - 1-5 cells thick, initiate keratinization - flatten, nuclei & organelles disintegrate (apoptosis), prominent cytoplasmic granules, keratohyalin granules - help to form keratin, lamellar granules - contain water-resistant glycolipid (lipid), epidermal water barrier, cut off from nutrients - Stratum lucidum (clear layer) - Thin translucent band, transition region between s. Granulosum and s. corneum, indistinct boundaries between dead keratinocytes, tonofilaments - product of keratohyalin granules clings to intracellular keratin filaments generating parallel arrays, cut off from nutrients - Stratum corneum (horny layer) - 20-30 cell layers thick, anucleate keratinocytes, outermost layer - protect against abrasion and penetration, glycolipid from lamellar granules creates near

waterproof layer, terminal cells are cornified (horny) - dandruff and dander, shed 50,000 cells per minute - 40 lb in a lifetime, callus formation - repeated pressure - Thickness of epidermis varies according to location - Skin layers are held together by desmosomes and hemidesmosomes - The dermis is a connective tissue layer binding the body together - Papillary layer (20% of thickness) - Loose areolar CT, dermal papillae (meissner corpuscle, free nerve endings, capillaries), blisters - Reticular layer (80% of thickness) - Dense irregular CT (collagen and elastic fibers - striae/stretch marks), blood vessels and accessory structures (sweat and sebaceous glands, pacinian corpuscle) Explain the importance of epidermal ridges and cleavage lines - Epidermal ridges (friction ridges) form fingerprints - In thick skin dermal papillae are arranged into dermal ridges, dermal ridges indent epidermis, enhanced grip strength, genetically determined - individual specific, sweat pores help generate fingerprints - Cleavage lines and flexure lines are generated by the dermis - Cleavage lines are gaps in the bundles of collagen fibers that make up the dermis - Flexure lines are dermal folds that occur at or near a joint Explain where melanin is synthesized and why it is so important to skin health - Melanin ranges from orange-red to black- providing pigment to keratinocytes - Synthesized from tyrosine - increased by UV radiation - Melanin absorbs UV radiation to protect keratinocyte DNA (shielding like an umbrella) - All humans contain the same number of melanocytes, but vary in kind and amount of melanin produced - Carotene: accumulates in stratum corneum of thick skin giving a yellow-orange pigment - Hemoglobin: crimson color of oxygenated blood Describe the accessory structures of skin and their physiological functions - Nails, hair, glands (sweat and oil), all derived from the epithelium - Nails are scale-like modifications of the epidermis - Hard keratin- cells do not flake off, nail matrix - nail growth - Clinical indicator: yellow tinge - respiratory or thyroid disorder, thickened yellow fungal infection, concavity (spoon nail) - iron deficiency, horizontal lines (beau’s lines) malnutrition - Hair (pili) consists of dead, keratinized cells - Hard keratin - cells do not flake off, hair shaft and hair root, 3 concentric layers medulla, cortex, cuticle; hair follicle, hair bulb - hair follicle receptor (touch), arrector pili smooth muscle - Sweat glands have ducts that release sweat onto skin - Eccrine sweat glands

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More abundant, duct extends to a pore at skin surface, merocrine secretion of sweat, sweat is 99% water (salts, waste, antibodies, dermcidin), sympathetic regulation - forehead to toes, “cold sweat” - emotional - Apocrine sweat glands - Axillary and anogenital, duct empty into hair follicle, merocrine secretion of sweat with fatty substances and proteins, bacteria on skin produce odor, sympathetic regulation - stress, human sexual scent glands - Hair, sweat, and blood vessels in the skin all contribute to regulating body heat - Sebaceous glands (oil glands) secrete sebum - Everywhere except palms and soles, holocrine secretion of sebum, sebum is an oily lipid lubricant (lubrication, slow water loss, bactericidal), outgrowth of hair follicle, arrector pili contractions force sebum out - Skin is a critical barrier between body and environment (first line of defense) - Chemical barrier - Acid mantle - low pH of skin secretions - Sweat (dermcidin), sebum (bactericide) - Defensins - Melanin - chemical sunscreen - Physical barrier - Bricks and mortar - dead keratinocytes and glycolipids - Water-resistance - preventing loss and entry - Organic solvents & heavy metals can cross - Biological barrier - Dendritic cells - Dermal macrophages - DNA converts UV radiation to heat Explain how skin and accessory structures can be used diagnostically - Erythema (redness) - fever, hypertension, inflammation, allergy, embarrassment - Pallor (blanching/pale skin) - anemia, low BP, anger, fear, stress - Jaundice (yellow) - liver disorder (bile accumulation in blood) - Bronzing (metallic appearance) - Addison’s disease (pituitary gland tumor) - Cyanosis (blue) - low amounts of hemoglobin and/or RBCs - Burns denature cell proteins and kill cells of the skin - 1st degree burn involves epidermis only - 2nd degree burn involves epidermis and part of all of the dermis - 3rd degree burn involves epidermis, dermis, hypodermis, and possibly deeper - Skin cancer most often results from overexposure to UV radiation - ABCD rule - Asymmetry: two sides of pigmented spot/mole do not match - Border irregularity: borders of lesion exhibit indentations - Color: pigmented spot contains several colors - Diameter: spot is larger than 6 mm in diameter - Evolution: changes with time

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Basal cell carcinoma: stratum basale proliferation, common- 80% of all skin cancers Squamous cell carcinoma: stratum spinosum proliferation Melanoma: melanocyte proliferation, highly metastatic, chemotherapy resistant...