1. Skin; The integumentary system

2. Skin
Organ composed of many tissues
Thin, yet still one of the largest organs of the
body

3. Dermatology
Medical specialty in diagnosis and treatment of
skin disorders

4. Physiology of the integument
Regulation of temp
Protection
Sensory reception
Excretion (and absorption)
Synthesize Vit. D
Immunity (langerhans’ cells)

5. Cutaneous sensation

6. Anatomy of the Integument

8. 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

10. Learning check
Which stratum of the epidermis is immediately
superficial to the stratum basale
Stratum spinosum

11. 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

12. Skin colors
Two pigments
– Melanin in epidermis
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Produced by melanocytes, brown pigment
Lack of melanin = albinism
Patches of melanin = freckels
Patches without melanin = vitiligo
– Carotene in corneum and dermis
• Yellowish hue

13. Keratinization
• As cells move from deep layers to superficial
layers, keratin accumulates
• Cells die as they move superficially

14. Accessory Structures of Skin
Skin glands
– Sebaceous/sudoriferous/ceruminous/mammary
Hair
Nails

15. 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)

16. 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

17. Acne

18. 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

19. 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

21. Nail anatomy
Plates of packed, hard, keratinized cells
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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

22. Nail function
Grasp and manipulate
Protect
Scratch!

24. 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

25. 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)

26. 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

28. 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)

29. 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

30. 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

33. 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

36. 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

37. Eczema

38. Psoriasis