1. The Integumentary System

2. Overview Largest organ (15% of body weight) 3 layers: Epidermis Dermis
keratinized stratified squamous epithelium
Dermis
connective tissue layer
Hypodermis
Adipose & blood vessels

3. Structure of the Skin

4. Functions of the Skin
Resistance to trauma and infection (slightly acidic)
Barrier to UV light
Vitamin D synthesis
Sensory receptors
Thermoreceptors
Nonverbal communication

5. Cells of the Epidermis Stem cells = undifferentiated cells
Keratinocytes = waterproofing
Melanocytes = make pigment that shields UV
Tactile (Merkel) cells = sense of touch
Dendritic (Langerhans) cells = fights pathogens

6. Cell and Layers of the Epidermis

7. Figure 6.2a

8. Stratum Basale Single layer on basement membrane
Cell types in this layer
keratinocytes – divide to replace epidermis
melanocytes
Merkel cells

9. Stratum Spinosum Cell types: keratinocytes
dendritic (Langerhans) cells

10. Stratum Granulosum 3 to 5 layers Flat keratinocytes
Produces lipid-filled vesicles that waterproof the skin
forms a barrier between surface cells and deeper layers
cuts off surface strata from nutrient supply, so top layers are dead

11. Stratum Lucidum Thin translucent zone seen only in thick skin
Keratinocytes
Cells have no nucleus or organelles

12. Stratum Corneum Up to 30 layers of dead, scaly, keratinized cells
surface cells flake off (exfoliate) – forms dust

13. Life History of Keratinocytes
Produced by stem cells in stratum basale
New cells push others toward surface
Cells filled with keratin
Cells die and exfoliate

14. Dermis Thickness = 0.6mm to 3mm Composition
collagen, elastic and reticular fibers, fibroblasts
Dermal papillae - extensions of the dermis into the epidermis
forming the ridges of the fingerprints
2 Layers
papillary layer - top
reticular layer - bottom

15. Hypodermis Subcutaneous Mostly adipose Functions energy reservoir
thermal insulation
Hypodermic injections (subQ)
highly vascular

16. Skin Colors (Pigmentation)
Hemoglobin = red pigment of red blood cells
Carotene = yellow pigment
concentrates in stratum corneum and fat
Melanin = yellow, brown, and black hues
pigment synthesis stimulated by UV radiation

17. Abnormal Skin Colors 1
Cyanosis = blueness from deficiency of oxygen in the blood (cold weather)
Erythema = redness due to dilated cutaneous vessels (anger, sunburn, embarrassment)
Jaundice = yellowing of skin and sclera due to excess of bilirubin in blood (liver disease)

18. Cyanosis

19. Erythema

20. Jaundice

21. Abnormal Skin Colors 2
Bronzing = golden-brown color of Addison disease
Pallor = pale color from lack of blood flow
Albinism = a genetic lack of melanin
Hematoma = a bruise (visible clotted blood)

22. Addison’s Disease

23. Albinism

24. Albinism in animals

25. Hematoma

26. Skin Markings Hemangiomas (birthmarks)
discolored skin caused by benign tumors of dermal blood capillaries (strawberry birthmarks disappear in childhood -- port wine birthmarks last for life)
Freckles and moles = group of melanocytes
freckles are flat; moles are elevated
Friction ridges leave oily fingerprints on touched surfaces
unique pattern formed during fetal development
Flexion creases form after birth by repeated closing of the hand
Flexion lines form in wrist and elbow areas

27. Characteristics of Human Hair
Hair (composed of hard keratin)
Hair found almost everywhere
differences between sexes or individuals is difference in texture and color of hair
3 different body hair types
lanugo -- fine, unpigmented fetal hair
vellus -- fine, unpigmented hair of children and women
terminal hair -- coarse, long, pigmented hair of scalp

28. Structure of Hair and Follicle
Hair is filament of keratinized cells
shaft = above skin; root = within follicle
Follicle is oblique tube within the skin
bulb is where hair originates
vascular tissue (papilla) in bulb provides nutrients
Texture and shape of hair
straight hair = round; wavy = oval
Hair color = pigment in cells of cortex

29. Hair Color and Texture, Brunette
Eumelanin pigment colors brown and black hair.

30. Hair Color and Texture, Blonde
Blond hair contain pheomelanin pigment, but little eumelanin.

31. Hair Color and Texture, Red
Red hair contains little eumelanin but lots of pheomelanin.

32. Hair Color and Texture, Gray and White
White hair = air in medulla and lack of pigment in cortex. Gray hair is a mixture of white and pigmented hairs.

33. Structure of Hair Follicle
Epithelial root sheath
Connective tissue root sheath
Hair receptors entwine each follicle
Piloerector muscle
goose bumps

34. Hair Growth and Loss Hair cycle = 3 repeating cycles
anagen is growth stage (90% of scalp follicles)
lasts 6-8 years in young adult
catagen is shrinking follicle (lasts 2-3 weeks)
telogen is resting stage (lasts 1-3 months)
Thinning or baldness = alopecia
Pattern baldness = genetic and hormonal
sex-influenced trait(dominant in males, recessive in females); expressed only with high testosterone levels
Hirsutism = excessive hair growth
hormone imbalance (ovary or adrenal cortex problem)

35. Functions of Hair Body hair (too thin to provide warmth) Scalp hair
alert us to parasites crawling on skin
Scalp hair
heat retention and sunburn cover
Beard, pubic and axillary hair indicate sexual maturity and help distribute sexual scents
Guard hairs and eyelashes
prevent foreign objects from getting into nostrils, ear canals or eyes
Expression of emotions with eyebrows

36. Fingernail Structure

37. Nails Derivative of stratum corneum
densely packed cells filled with hard keratin
Flat nails allow for fleshy, sensitive fingertips
Growth rate is 1 mm per week
new cells added by mitosis
nail plate is visible part of nail
medical diagnosis of iron deficiency = concave nails

38. Sweat (Sudoriferous) Glands
Purpose = cool us down
500 ml of insensible perspiration/day
sweating with visible wetness = diaphoresis
2 types of sweat glands:
Eccrine – all over body
Apocrine glands – mainly axillary regions
produce sweat containing fatty acids
found only near hair follicles and respond to stress and sex
bromhidrosis is body odor produced by bacterial action on fatty acids

39. Oil (Sebaceous) Glands
Sebaceous- oily secretion called sebum that contains broken-down cells
lanolin in skin creams is sheep sebum
opens into hair follicle

40. Ceruminous Glands Found only in external ear canal
Their secretion combines with sebum to produce earwax
waterproof keeps eardrum flexible
bitterness repel mites and other pests

41. Mammary Glands
Develops in female breasts at puberty (male glands do not develop)
Function: produce milk after pregnancy
Additional nipples (polythelia)

42. Skin Cancer Induced by UV rays of the sun
basal cell carcinoma (least dangerous)
arises from stratum basale and invades dermis
With surgery 99% survival rate
squamous cell carcinoma
arises from keratinocytes in stratum spinosum
metastasis to the lymph nodes can be lethal
malignant melanoma (most deadly)
arises from melanocytes of a preexisting mole

43. Figure 6.11a

44. Figure 6.11b

45. Figure 6.11c

46. ABCD Rule by American Cancer Society
A: A symmetry-the 2 sides of the pigmented spot or mole do not match
B: Border irregularity-borders of the lesion are not smooth, but exhibit indentations
C: Color- the pigmented spot contains several colors
D: Diameter-spot larger than 6 mm
(E: Elevation)

47. Burns
Hot water, sunlight, radiation, electric shock or acids and bases
Death from fluid loss and infection
Degrees of burns
1st-degree = only the epidermis (red, painful and edema)
2nd-degree = epidermis and part of dermis (blistered)
epidermis regenerates from hair follicles and sweat glands
3rd-degree = epidermis, dermis and more is destroyed
often requires grafts or fibrosis and disfigurement may occur
Treatment – IV nutrition and fluid replacement, remove dead tissue, and infection control

48. Figure 6.12

49. Figure 6.12ab

50. Figure 6.12bb

51. Figure 6.12cb

52. UVA, UVB and Sunscreens
UVA and UVB are improperly called “tanning rays” and “burning rays”
Both thought to initiate skin cancer
As sale of sunscreens has risen so has skin cancer
those who use have higher incidence of basal cell
chemical in sunscreen damage DNA and generate harmful free radicals
PABA, zinc oxide and titanium dioxide
“ Dear 16 year old Me”

53. Skin Grafts and Artificial Skin
Third-degree burns require skin grafts
Graft options
autograft -- tissue from patient
isograft -- tissue from identical twin
cultured keratinocyte patches
Temporary grafts (immune system)
homograft (allograft) -- from unrelated person
heterograft (xenograft) -- from another species
amnion from afterbirth
artificial skin from silicone and collagen