Skin

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Skin

  1. 1. Skin; The integumentary system
  2. 2. Skin Organ composed of many tissues Thin, yet still one of the largest organs of the body
  3. 3. Dermatology Medical specialty in diagnosis and treatment of skin disorders
  4. 4. Physiology of the integument Regulation of temp Protection Sensory reception Excretion (and absorption) Synthesize Vit. D Immunity (langerhans’ cells)
  5. 5. Cutaneous sensation
  6. 6. Anatomy of the Integument
  7. 7. Structural layers Epidermis (listed superficial to deep) – Stratum corneum (dead) – Stratum lucidum (only in palms, soles, digit tips) – Stratum granulosum (make lipid rich secretions) – Stratum spinosum (appear to have spines) – Stratum basale (proliferative stem cells) • AKA stratum germinativum
  8. 8. Learning check Which stratum of the epidermis is immediately superficial to the stratum basale Stratum spinosum
  9. 9. Structural layers Dermis – Papillary region • Areolar tissue, finger like projections; produce fingerprints • Some have Meissner corpuscles and free nerve endings – Reticular • Dense irregular tissue • Tears in this region cause stretch marks • Contain, hair follicles, adipose, nerves, oil glands and sweat gland ducts
  10. 10. Skin colors Two pigments – Melanin in epidermis • • • • Produced by melanocytes, brown pigment Lack of melanin = albinism Patches of melanin = freckels Patches without melanin = vitiligo – Carotene in corneum and dermis • Yellowish hue
  11. 11. Keratinization • As cells move from deep layers to superficial layers, keratin accumulates • Cells die as they move superficially
  12. 12. Accessory Structures of Skin Skin glands – Sebaceous/sudoriferous/ceruminous/mammary Hair Nails
  13. 13. Glands Sudoriferous – Eccrine • Almost everywhere • Dense ~ 3000 per in2 in your palms – Apocrine • Originally thought to be apocrine, actually exocytotic • Develop at puberty • Arm pits, groin, areola, bearded region in guys Ceruminous – In your ears; produce ear wax (cerumen)
  14. 14. Glands Sebaceous – secrete oil (sebum) – Usually connected to hair follicles – Absent in palms and soles – Small in trunk / limbs – Large in face, neck, chest Mammary – secrete milk
  15. 15. Acne
  16. 16. Hair Function – protection, sensation Structure - Shaft and Root – Shaft; superficial, projects from surface – Root; deep to the shaft • Medulla / Cortex / Cuticle – Hair follicle; surrounds root • Internal and external sheath layers
  17. 17. Hair Bulb – onion shaped base of follicle – Papilla; indentation filled with blood vessels – Matrix; germinal (proliferative) cells, produce the hair – Lose 70-100 hairs from scalp per day
  18. 18. Nail anatomy Plates of packed, hard, keratinized cells – – – – – – Nail body - seen Free edge – projection past finger tip Nail root – deep to cuticle Lunula – can’t see deep vessels Eponychium (cuticle) Matrix – cells divide to produce nail, cells pushed distally over stratum basale
  19. 19. Nail function Grasp and manipulate Protect Scratch!
  20. 20. Epidermal (superficial) wound healing Abrasions and minor burns, may extend to dermis Only epidermal cells involved (no connective) Cells adjacent to wound break away from basement membrane Cells migrate in to wound area Migration discontinues as cells collide (contact inhibition) Hormone (EGF) stimulates cell division Relocated cells divide and build new strata
  21. 21. Deep wound healing Injury extends in to dermis and subcutaneous More complex as more tissue types involved Bleeding and clotting  scab formation Scar may form Healed tissue may lose some function(s)
  22. 22. Deep wound healing Four phases of healing: – Inflammatory – more blood flow, bleeding, white blood cells attack bacteria – Migratory – clot becomes scab, epithelial cells move under scab – Proliferative – epithelial cells divide – Maturation – scab falls off when epidermis restored
  23. 23. Scars and scar formation Fibrosis – scar formation Scar tissue typically has fewer blood vessels, fewer hairs, fewer glands, fewer sensory structures but more dense collagen – Hypertrophic scar may extend above (higher than) epidermis, but will not be wider than original wound – Keloid scar extends beyond original wound in to undamaged (normal tissues)
  24. 24. Aging skin Decreased collagen (skin isn’t as tough) Elastin loses elasticity (skin tears instead of stretches Fibroblasts, white blood cells less efficient and decrease in number Blood vessels increasingly permeable (more easily bruise) Oil production decreases Thinner skin Slower healing
  25. 25. Skin disorders / disease Skin cancer – Basal cell carcinoma (arise from cells in stratum basale) ~78% of all skin cancers, rarely metastasize – Squamous cell ~20% of all skin cancers, sometimes metastasize – Melanoma (arise from melanocytes) – usually and rapidly metastasize
  26. 26. Skin disorders / disease Burns – caused by excessive heat, electricity, radioactivity, or corrosive chemical exposure – 1st degree • Erythema (redness) and pain, no blisters – 2nd degree • Destroys epidermis and part of dermis, • Erythema, blister formation, edema, pain. Blister is separation of epidermis from dermis from fluid accumulation – 3rd degree (aka full thickness burn) • Destroys epidermis and dermis • May be marble white to mahogany (charred black) • Locally numb due to destruction of sensory nerve endings, adjacent area very painful
  27. 27. Skin disorders / disease • Eczema – Chronic inflammation, edema, itching, dryness, cracking flaking skin • Psoriasis – Reddish raised plaques of tissue on skin – Not contagious – Auto-immune mediated disease. Own immune system attacks skin cells, results in over production of skin
  28. 28. Eczema
  29. 29. Psoriasis

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