1. Chapter 5 Integumentary System
Shaft of a hair protruding through the skin
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2. Integumentary System skin, hair, glands, nails Functions Protection
Against abrasion and UV light
Prevents entry of microorganisms
Prevents dehydration
Sensation
Sensory receptors detect heat, cold, touch, pressure, pain
Temperature regulation by controlling
Blood flow through skin
Sweat gland activity
Vitamin D production
Excretion of small amounts of waste products

3. Skin SA – 1.2-2.2 m2 and weighs 4-5 kg (9-11 lbs)!! 3 major regions
Epidermis: outermost region (superficial)
Resists abrasion
Reduces water loss
Dermis: middle region (bulk of skin)
Responsible for most structural strength of skin
Leather produced from dermis of animals…ewww.
Subcutaneous tissue (hypodermis): deepest region
Not really part of skin
Connects skin to underlying muscle or bone

4. Fig. 5.1

5. Tab. 5.1

6. Epidermis keratinized stratified squamous epithelium
4 distinct cell types
4-5 layers
Outer portion exposed to external environment
protection

7. 4 Cell Types of Epidermis
Keratinocytes
Most abundant
Produce fibrous protein keratin
Gives skin its protective properties
Melanocytes
Produce brown pigment melanin
Found in deepest layers of epidermis
Langerhans’ cells
Epidermal macrophages
Help activate immune system
Merkel cells
Touch receptors in association with sensory nerve endings

8. Layers of Epidermis Stratum Basale (Basal Layer)
Deepest, firmly attached to dermis
Structural strength provided by desmosomes and hemidesmosomes
single row of youngest keratinocytes
Cells undergo mitotic divisions ~every 19 days
10-25% are melanocytes

9. Layers of the Epidermis
Stratum Spinosum
Melanin granules and Langerhans’ cells abundant
Melanin taken up by keratinocytes, accumulates on “sunny side” to protect nucleus from UV damage
Stratum Granulosum
Drastic changes in keratinocyte appearance
Keratohyaline and lamellated bodies (waterproofing) accumulate in cells
Above this layer epithelial cells die because too far from dermis

10. Layers of the Epidermis
Stratum Lucidum
Thin, transparent band superficial to S. Granulosum
few rows of flat, dead keratinocytes
only in thick skin (soles, palms)
Stratum Corneum
Outermost layer of keratinized cells
¾ of epidermal thickness
20-30 cell layers thick, all dead
Millions rub off everyday. Totally new every days.
Functions:
Waterproofing
Protection from abrasion and penetration
Rendering body relatively insensitive to biological, chemical, and physical assaults

11. Fig. 5.2b

12. Fig. 5.3

13. Thick and Thin Skin Only 4 strata all 5 epithelial strata
fewer cell layers per stratum
lucidum usually absent
Hair found only in thin skin
all 5 epithelial strata
Stratum lucidum
No hair

14. Skin Color
Melanocytes produce melanin inside melanosomes (vesicles, from golgi), then transfer melanin to keratinocytes
size and distribution of melanosomes determine skin color
genetic but influenced by UV (tanning) and hormones
Increased blood flow produces red skin color (Erythema)
decreased flow causes pale skin
Decreased oxygen content in blood  bluish color (cyanosis)
Carotene, ingested plant pigment, can cause skin to appear yellowish

15. Fig. 5.4

16. Dermis 2nd major skin region strong, flexible conn tissue
Cell types: fibroblasts, a few adipose cells, macrophages
2 layers:
papillary
reticular

17. Papillary layer of Dermis
Areolar conn tissue w/collagen & elastic fibers
superior surface- peg-like projections “dermal papillae”
Genetic
fingerprints & footprints
Contains blood vessels that supply overlying epidermis
With nutrients
Remove waste products
Aid in regulating body temperature

18. Reticular layer of Dermis
Dense irregular conn tissue
~80% of thickness of skin
Collagen fibers add strength and resiliency to skin
Elastin fibers provide stretch-recoil properties
Striae (stretch marks) caused when skin overstretched, dermis ruptures and leaves visible lines

19. Reticular layer
Elastin and collagen fibers oriented more in one direction than in others
produce cleavage, or tension, lines
Fig. 5.5

20. Subcutaneous Tissue Deep to the skin
Adipose (primarily) and areolar connective tissue
Not really part of skin
Stores fat, connects skin to underlying structures (mainly muscles)
Shock absorber, insulator
Increases as you gain weight

21. Hair
Lanugo (fetal hair) replaced near time of birth by terminal hairs (scalp, eyelids, eyebrows) and vellus hairs
At puberty, vellus hairs replaced with terminal hairs
Hairs are columns of dead, keratinized epithelial cells
Each hair consists of
shaft above skin
root below skin
hair bulb - site of hair formation
growth stage and resting stage
Contraction of arrector pili, smooth muscles, causes hair to “stand on end”  “goose bumps”

22. Fig. 5.6

23. Sebaceous Glands Simple or compound alveolar glands
found all over body except palms & soles
Soften skin when stimulated by hormones
Secrete oily secretion called sebum
Acne: active inflammation of sebaceous glands

24. Sweat Glands Different types prevent overheating of body
Secrete cerumen and milk
Up to 3 million/person
Merocrine sweat glands produce sweat, cools body: most numerous in palms and soles
Apocrine sweat glands: axillary and genital areas. Ducts empty into hair follicles. Produce organic secretion, broken down by bacteria to cause body odor
Ceruminous glands: modified merocrine glands in external ear canal, secrete cerumen (ear wax)
Mammary glands: specialized sweat glands, secrete milk

25. Fig. 5.7

26. Nails nail is Stratum Corneum containing hard keratin
nail root covered by skin
nail body = visible part of nail
Nearly all nail formed by nail matrix, but nail bed contributes
lunula = part of nail matrix visible through nail body (white “crescent”)

27. Fig. 5.8

28. 5 Integumentary System Functions
1. Protection
Skin
Protects against abrasion, UV
Prevents entry of microorganisms
Helps regulate body temperature
Prevents water loss
Hair
heat insulator
Nails protect ends of digits
2. Sensation
sensory receptors for
heat
cold
touch
pressure
pain

29. Integumentary System Functions
3.Temp Regulation
Skin
Controls heat loss from body (dilation and constriction of blood vessels)
Sweat glands
Produce sweat, evaporates, lowers body temperature
4. Vitamin D Production
UV stimulates production of a precursor molecule in skin that’s modified by liver and kidneys into vit D
Vit D increases calcium uptake in intestines
5. Excretion
Skin glands remove small amounts of waste products but not important in excretion

30. Blood Vessel Dilation, Fig. 5.9

31. Cancer: Basal Cell Carcinoma
Least malignant and most common skin cancer
Stratum Basale cells proliferate and invade dermis and hypodermis
Slow growing, do not often metastasize
99% Can be cured by surgical excision

32. Squamous Cell Carcinoma
Arises from keratinocytes of Stratum Spinosum
Arise most often on scalp, ears, lower lip
Grows rapidly, metastasizes if not removed
Prognosis is good if treated by radiation therapy or removed surgically

33. Melanoma Cancer of most dangerous type of skin cancer because it is:
Likely to metastasize
Resistant to chemotherapy

34. Melanomas
ABCD rule
A: Asymmetry; the 2 sides of pigmented area do not match
B: Border irregular w/indentations
C: Color (pigmented area) is black, brown, tan, sometimes red or blue
D: Diameter larger than 6 mm (size of a pencil eraser)
Treated by wide surgical excision accompanied by immunotherapy
Chance of survival is poor if lesion is over 4 mm thick

35. Burns First-degree: only epidermis is damaged
localized redness, swelling, pain
Second-degree: epidermis and upper regions of dermis damaged
Symptoms mimic first degree burns
blisters also appear
Third-degree: entire thickness of skin is damaged
Burned area appears gray-white, cherry red, or black;
no initial edema or pain
nerve endings are destroyed

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37. Rule of Nines Estimates severity of burns Divides body into areas
~ 9%, or multiples of 9%, of total body area
Younger patients are different
Burns considered critical if:
Over 25% of body has 2nd degree burns
Over 10% of body has 3rd degree burns
3rd degree burns on face, hands, or feet

38. Effects of Aging on the Integumentary System
Epidermal replacement of cells slows and skin becomes thinner
Decreased elasticity and loss of subcutaneous tissue leads to wrinkles
Subcutaneous fat layer diminishes, leading to intolerance of cold
Skin becomes dry and itchy
Sweat and sebaceous glands are less active
number of melanocytes decreases

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