1. Chapter 5 Integumentary System
Shaft of a hair protruding through the skin
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2. Functions of the Integumentary System
Consists of the skin, hair, glands, and nails
Functions
Protection
Against abrasion and UV light
Prevents entry of microorganisms
Prevents dehydration
Sensation
Sensory receptors that can detect heat, cold, touch, pressure, and pain
Temperature regulation by controlling
Blood flow through the 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)!!
Consists of three major regions
Epidermis: outermost region (superficial)
Resists abrasion
Reduces water loss
Dermis: middle region (bulk of skin)
Responsible for most of the structural strength of the skin
Leather is produced from the dermis of animals…ewww.
Subcutaneous tissue (hypodermis): deepest region
Not really part of the skin
Connects the skin to underlying muscle or bone

4. Fig. 5.1

5. Tab. 5.1

6. Epidermis
Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers
Cell types include keratinocytes, melanocytes, Merkel cells, and Langerhans’ cells
Outer portion of the skin is exposed to the external environment and functions in protection

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

8. Layers of the Epidermis
Stratum Basale (Basal Layer)
Deepest epidermal layer firmly attached to the dermis
Structural strength is provided by desmosomes and hemidesmosomes
Consists of a single row of the 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 are abundant in this layer
Melanin is taken up by the keratinocytes and accumulates on the “sunny side” to protect the nucleus from UV damage
Stratum Granulosum
Drastic changes in keratinocyte appearance occurs
Keratohyaline and lamellated bodies (waterproofing) accumulate in the cells of this layer
Above this layer the epithelial cells die because they are too far from the dermis

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

11. Fig. 5.2b

12. Fig. 5.3

13. Thick and Thin Skin Only four epithelial strata
contains fewer cell layers per stratum
Stratum lucidum is usually absent
Hair is found only in thin skin
has all five epithelial strata
Stratum lucidum
No hair

14. Skin Color
Melanocytes produce melanin inside melanosomes (vesicles, from golgi), then transfer the melanin to keratinocytes
The size and distribution of melanosomes determine skin color
Melanin production is determined genetically but can be influenced by UV light (tanning) and hormones
Increased blood flow produces a red skin color (Erythema), whereas a decreased flow causes pale skin
Decreased oxygen content in the blood results in a bluish color called cyanosis
Carotene, an ingested plant pigment, can cause the skin to appear yellowish

15. Fig. 5.4

16. Dermis
Second major skin region containing strong, flexible connective tissue
Cell types include fibroblasts, a few adipose cells and macrophages
Composed of two layers:
papillary and reticular

17. Layers of the Dermis Papillary layer
Areolar connective tissue with collagen and elastic fibers
Its superior surface contains peg-like projections called dermal papillae
Genetically determined
Responsible for fingerprints and footprints (films of sweat)
Contains blood vessels that supply the overlying epidermis
With nutrients
Remove waste products
Aid in regulating body temperature

18. Layers of the Dermis Reticular layer Dense irregular connective tissue
Accounts for approximately 80% of the thickness of the skin
Collagen fibers in this layer add strength and resiliency to the skin
Elastin fibers provide stretch-recoil properties
Striae (stretch marks) are caused when skin is overstretched, the dermis ruptures and leaves visible lines

19. Layers of the Dermis Reticular layer
Elastin and collagen fibers are oriented more in one direction than in others and 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 the skin
Stores fat and connects the skin to the underlying structures (mainly muscles)
Shock absorber and insulator
Increases greatly as you gain weight

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

22. Fig. 5.6

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

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

25. Fig. 5.7

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

27. Fig. 5.8

28. Integumentary System Functions
Protection
Skin
Protects against abrasion and UV light
Prevents the entry of microorganisms
Helps regulate body temperature
Prevents water loss
Hair
Acts as a heat insulator
Nails protect the ends of the digits
Sensation
Skin contains sensory receptors for
heat
cold
touch
pressure
pain

29. Integumentary System Functions
Temperature Regulation
Skin
Controls heat loss from the body by dilation and constriction of blood vessels
Sweat glands
Produce sweat, which evaporates and lowers body temperature
Vitamin D Production
UV light stimulates the production of a precursor molecule in the skin that is modified by the liver and kidneys into vitamin D
Vitamin D increases calcium uptake in the intestines
Excretion
Skin glands remove small amounts of waste products but are not important in excretion

30. Blood Vessel Dilation, Fig. 5.9

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

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

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

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

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

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37. Rule of Nines Estimates the severity of burns
Divides body into areas that are ~ 9%, or multiples of 9%, of the total body area
Younger patients are different
Burns considered critical if:
Over 25% of the body has second-degree burns
Over 10% of the body has third-degree burns
There are third-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, and the number of melanocytes decreases

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