The Integumentary System

The Integumentary System

The Integumentary System I. Functions: A. Protection B. Temperature regulation C. Excretion D. Vitamin D synthesis (calcitriol) E. Sensation II. Anatomy of the skin

A. Three regions 1. Epidermis (surface coat) stratified epithelium 2. Dermis (bulk of the skin) dense irregular connective 3. Hypodermis (subcutaneous layer) loose conn tissue, adipose B. Layers of Epidermis

1. Stratum Corneum- superficial keratin (hard, H2O insoluble protein) keratinocytes originate deep (can become dandruff, callus) 2. Stratum Lucidum only in thick skin 3. Stratum granulosum- keratinocytes

die 4. Stratum spinosum - Langerhans cells 5. Stratum basale - deep layer near dermis - keratinocyte division, melanocytes C. Cells of the Epidermis 1. Keratinocytes (90% of epidermal cells)

2. Melanocytes- (2-3% of cells) - brown skin pigment aids in UV light absorption - can increase /decrease production 3. Langerhans cells - <1% cells, immune 4. Merkel cell - touch sensation D. Dermis layer of the skin

1. Composition: Gel matrix (hydrated)fibers:collagen, elastin Cells: Fibroblasts Macrophages Leukocytes, mast cells (heparin) 2. Layers of the Dermis: a. Papillary layer(boundary) - areolar tissue

- free nerve endings, papilla (fingerprints) - exchange of materials, attachment b. Reticular layer- tough dense irregular tissue - striae & flexure lines E. Subcutaneous Layer 1. Composition - Loose connective tissue

soft gel (water + collagen), elastin, fewer fibers than dermis - Fat (adipose) variable amount cushions, skin contours, insulator, energy depot F. Skin derivatives 1. Sweat glands (sudoriferous) eccrine- thermoregulation

apocrine- associated with hair follicle 2.Sebaceous gland (oil) ubiquitous empties into hair follicle,skin 3. Hair Column of keratinized cells epidermal cells of follicle extends into the dermis

growth /rest activity is cyclical - vellus vs. terminal Hair loss, Alopecia arrector pili- smooth muscle 4. Nails (fingers, toes) Analogous to hair - keratin in stratum corneum but not melanocytes Protective Function

Skin Color (pigments): 1. Melanin (yellow-brown-black) 2. Carotene (yellow- orange) - accumulates in corneum 3. Hemoglobin (red) erythema vs. cyanosis Influenced by blood flow, liver (jaundice)

Aging changes to Integument I. Aging vs. Abnormal changes A. Effects of Sunlight on epidermis - DNA damage - keratinocytes irregular - melanocytes less evenly distributed - decreased Langerhans cell number

Warren (1991) no difference until after age 45, more wrinkles, less elasticity with > 12 hr /wk for previous yr B. Sunlight effects on Dermis: - increase number but irregular elastin fibers (shape/ arrangement) elastosis - blood vessels decrease

CLASS ACTIVITY Many tanning salons claim to use the longersafe wavelengths of UV light (UVA). Based on the slide I will show discuss the validity of this claim: 1.List the potential side of effects of UVA vs,UVB light. 2. Groups vote as to which is

more dangerous. UVA ( tanning salon) (UVA weaker) vs. UVB (sunburn) more intense burn more penetrating (more reaches earth)

dermis- collagen epidermis blood vessels melanin immune cataracts,retina

C. Neoplastic skin conditions 1. Uncontrolled cell production - benign or malignant 2. Skin cancers: basal cell squamous cell, malignant melanoma Asymmetry Border

Color Diameter 2. Due to several factors: - decreased inflammatory response, melanin, Langerhans, removal of harmful substances, increased cell irregularity - all of these also related to sunlight

exposure D. Other Preventable Aging effects 1. Effects of prolonged pressure (i.e. bedridden) - Bedsores (decubitus ulcers) decreased blood flow + thinning of subcutaneous fat II. Aging changes

A. Epidermis 1. More permeable corneum 2. Keratinocytes more variable - Strength of attachment, spacing of keratinocytes Rate of production

3. Melanocytes - uneven distribution (age spots) - reduced production of melanin - higher risk for sunburn and skin cancer due to sun exposure 4. Langerhans cells - numbers , allergic response

5. Hair - follicles - number of follicles inactive stage,thinner, made slower

(related to hormone changes) - air pockets, melanin( graying not chronological age) - decreased sebum 6. Nails - in growth (50%)

- reduced blood flow to extremities (toes) - more susceptible to injury, fungal infections, longer to repair B. Aging on Dermis 1. Collagen fibers

- decrease in amount - cross-linkages (stiffer, less resisting to pulling forces) in time cross links decrease, then increased skin tears 2. Elastin fibers - less well documented - thicker,clumped, stiffer - reduced ability to recoil

- some calcification - looser covering that hangs (1,2 due to fibroblast deficiency) 3. Immunity decline - WBC, mast cells, macrophages decline - reduced heparin (less vessel formation) 4. Mucopolysaccharides

- reduced water binding (shape, reduced movement of molecules) 5. Blood vessels - decrease number - increased thickness of basement membrane of endothelial cells slower delivery of nutrients, removal of wastes, decline of other skin structures

skin pallor, thermoregulation 6. Sweat glands - decreased # eccrine (except in scalp) - reduced threshold for sweating - decrease in apocrine secretion ( one positive!) 7. Sebaceous glands - no change #, increase in size but

decrease sebum production 8. Sensory neurons - no change in pain or touch receptors in hair follicles - other touch/pressure receptors - decreased sensory input from fingers, hands, areas with little hair Increase Risk of Vit D deficiency ( Ca2+):

Vit D (inactive form) synthesis in epidermis blood flow to bring cholesterol precursors ability to convert (> light for same result) ability to activate to calcitriol (kidney) ability to digest milk products C. Aging of Subcutaneous Layer

- ? Loose connective tissue - subcutaneous fat, not total body fat (sagging, loose skin appearance translucent skin appearance) Wrinkles, liver spot treatment

tretinoin (Retin-A) increased thickness epidermis increased turnover stratum corneum decreased #,size melanocytes increase in collagen, elastin dermal vessel dilation regression precancerous lesions RETIN-A: TOO GOOD TO BE TRUE? - redness, peeling, blistering,

swelling - increased sun sensitivity - 92% of cases skin inflammation - no long term studies- hairless, albino mice accelerated tumorigenic potential of UV radiation - interaction with abrasives

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