The Integumentary SystemI. Functions: A. Protection B. Temperature regulation C. Excretion D. Vitamin D synthesis (calcitriol) E. Sensation

II. Anatomy of the skinA. 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 Epidermis1. 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 die4. Stratum spinosum - Langerhans cells5. Stratum basale - deep layer near dermis- keratinocyte division, melanocytes

C. Cells of the Epidermis1. 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 -

D. Dermis layer of the skin1. Composition:Gel matrix (hydrated)- fibers:collagen, elastinCells: 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 follicle2. Sebaceous gland (oil) ubiquitous empties into hair follicle,skin

3. HairColumn of keratinized cellsepidermal 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 melanocytesProtective Function

Skin Color (pigments):1. Melanin (yellow-brown-black)2. Carotene (yellow- orange)- accumulates in corneum3. Hemoglobin (red)erythema vs. cyanosisInfluenced by blood flow, liver (jaundice)

Aging changes to IntegumentI. Aging vs. Abnormal changesA. 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 ACTIVITYMany 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) vs. UVB (sunburn)(UVA weaker) more intense burnmore penetrating(more reaches earth)dermis- collagen epidermisblood vessels melanin immune cataracts,retina

C. Neoplastic skin conditions1. Uncontrolled cell production - benign or malignant2. 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 effects1. Effects of prolonged pressure (i.e. bedridden)- Bedsores (decubitus ulcers) decreased blood flow + thinning of subcutaneous fat

II. Aging changesA. Epidermis1. More permeable corneum2. 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 exposure4. 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 Dermis1. 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, macrophagesdecline- 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 cellsslower delivery of nutrients, removal of wastes, decline of other skin structuresskin 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 outdoor activity

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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