2. The Integumentary System (Introduction)
Two major parts of the integumentary system Cutaneous membrane, or skin
2. Accessory structures
Hair
Exocrine glands
Nails

3. Cutaneous Membrane (Introduction)
Consists of two layers
Superficial epithelium, or epidermis
Underlying connective tissues of the dermis
Hypodermis, or subcutaneous layer
Loose connective tissue beneath the dermis
Separates integument from deeper tissues
Not part of the integumentary system, yet interwoven with connective tissue of the dermis

4. Figure 5-1 The General Structure of the Integumentary System.

5. Five General Functions of the Integument (Introduction)
Protection
Skin covers and protects underlying tissues
Prevents fluid loss
Temperature maintenance
Skin regulates heat exchange with the environment
Synthesis and storage of nutrients
Epidermis synthesizes vitamin D3
Dermis stores lipids in adipose tissue

6. Five General Functions of the Integument cont. (Introduction)
Sensory reception
Receptors detect touch, pressure, pain, and temperature and relay information to nervous system
Excretion and secretion
Glands excrete salts, water, and organic wastes
Specialized integumentary (mammary) glands secrete milk

7. The Epidermis (5-1) Composed of layered epithelial tissue
Avascular (contains no blood vessels)
Relies on diffusion from underlying connective tissue for nutrients and oxygen
Deepest cells (closest to the dermis) are most active
Cells in outer, superficial layers are dead
Majority of the cells are keratinocytes
Contain the protein keratin

8. Thick and Thin Skin (5-1)
Terms “thick” and “thin” refer to thickness of epidermis (not whole integument)
Thick skin – five layers of cells
Found on palms of hands and soles of feet
Very thick stratum corneum (outermost layer)
Total thickness about 0.5 mm (standard paper towel)
Thin skin – four layers of cells
Covers the rest of the body
Total thickness about 0.08 mm (plastic sandwich bag)

9. Figure 5-2a-b The Epidermis

10. Strata of the Epidermis (5-1)
Five cell layers (strata) of thick skin from deep to superficial
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum
Deep
Superficial

11. Figure 5-2b The Epidermis

12. Stratum Basale (5-1) Deepest layer of the epidermis
Attached to basement membrane by hemidesmosomes
Cells in the stratum basale
Basal cells
Stem cells that continually divide to replace cells lost at the surface
Merkel cells (sensitive to touch)
Melanocytes (synthesize pigment melanin)

13. Epidermal Ridges (5-1)
Formed by cells of the stratum basale extending down into dermis
Dermal projections (dermal papillae) extend up into epidermis between ridges
Ridges and papillae interlock
Increasing surface area for diffusion
Strengthening bond between layers
Contours of skin surface follow ridge patterns
Basis for fingerprints
Figure 5-2a-e The Epidermis

14. Intermediate Strata (5-1)
New daughter cells formed in stratum basale migrate upward toward skin surface
Cells progress through three intermediate layers
Stratum spinosum
Stratum granulosum
Stratum lucidum

15. Stratum Spinosum (5-1) Stratum spinosum (spiny layer)
Cells may continue to divide
Consists of keratinocytes held together by desmosomes
Contains branched dendritic cells (involved in the immune response)

16. Stratum Granulosum and Stratum Lucidum (5-1)
Stratum granulosum (grainy layer)
Cells have stopped dividing
Cells have started making keratin
Durable, water-resistant protein
Coats surface of skin and forms hair and nails
Stratum lucidum (clear layer)
Composed of flattened, densely packed cells filled with keratin

17. Stratum Corneum (5-1)
Contains 15–30 layers of flattened, dead cells packed with keratin
Called keratinized cells
Cells tightly connected by desmosomes
Because of connections, are generally shed in large groups or sheets

18. Cell Progression in the Epidermis (5-1)
Generally takes 7–10 days for cell to move from stratum basale to stratum corneum
In the process, cells fill with keratin and die
Dead cells stay in the stratum corneum for two more weeks before being shed or washed away

19. Skin Color – Pigmentation (5-2)
Carotene and melanin are the two pigments that influence skin color
Carotene
Orange-yellow pigment
Accumulates in epidermal cells
Found in orange-colored foods (carrots, squashes)

20. Skin Color – Pigmentation cont. (5-2)
Two types of melanin, red-yellow and brown-black
Made by melanocytes
Store melanin in vesicles called melanosomes
Activity increases in response to UV
Melanin absorbs UV radiation, protecting deeper layers of epidermis and dermis

21. Figure 5-3 Melanocytes.

22. Dermal Circulation and Skin Color (5-2)
Oxygenated blood is bright red
Increase in body temperature dilates superficial blood vessels in dermis
Result is a flushed, red skin color
Temporary constriction of the same vessels results in pale skin
Cyanosis, a bluish coloration, occurs when blood oxygen supplies are diminished

23. Beneficial Effects of Sunlight on Skin (5-3)
Vitamin D3
Formed by epidermal cells
Converted from a cholesterol steroid when epidermal cells exposed to sunlight
Liver and kidneys convert vitamin D3 into calcitriol
Essential for absorption of calcium and phosphorus
Inadequate vitamin D3 can lead to weak and flexible bones

24. Detrimental Effects of Sunlight on Skin (5-3)
Skin cancers
Any cancer of epithelial tissue is a carcinoma
Basal cell carcinoma is most common skin cancer
Originates in stratum basale
Squamous cell carcinoma found in more superficial layers
Malignant melanoma is most dangerous
Usually begins from a mole
Can metastasize through the lymphatic system
Figure 5-4 Skin Cancers.

25. The Dermis (5-4) Lies between the epidermis and hypodermis
Contains two major layers
Superficial papillary layer
Deeper reticular layer

26. The Dermal Papillary Layer (5-4)
Named after the dermal papillae
Consists of areolar tissue
Supports and nourishes epidermis
Contains capillaries, lymphatic vessels, and sensory neurons supplying skin surface

27. The Dermal Reticular Layer (5-4)
Interwoven meshwork of dense irregular connective tissue
Elastic fibers provide flexibility
Collagen fibers limit flexibility and so prevent damage to tissue
Dominant cell type is fibroblast
Accessory organs derived from epidermis (hair follicles, sweat glands) extend into this layer
Also contains: blood vessels, lymphatic vessels, nerve fibers, and sensory receptors

28. Figure 5-1 The General Structure of the Integumentary System.

29. The Hypodermis (5-5) Also called the subcutaneous layer
Deep to the dermis
Fibers intermixed with dermis, so no clear delineation
Not actually part of the integument
But stabilizes position of the skin relative to underlying tissues
Consists of areolar tissue with many fat cells
No vital organs in area make it an ideal site for subcutaneous injections

30. Hair and Hair Follicles (5-6)
Accessory structures of the integumentary system
Hairs
Nonliving, keratinized structures
Produced by hair follicles
Project above the skin surface everywhere except:
The sides and soles of the feet, palms of the hands, sides of the fingers and toes, the lips, and portions of the external genitalia

31. Hair Follicle Structure (5-6)
Project into dermis and usually into hypodermis
Walls contain all cell layers found in epidermis
Epithelium at the base of follicle forms cap over the hair papilla
Connective tissue that contains capillaries and nerves
Hair matrix surrounds hair papilla
Contains epithelial stem cells
Cells divide and push daughter cells toward surface

32. Figure 5-5b Hair Follicles and Hairs.

33. Hair Structure (5-6)
As hair cells move toward surface, they become keratinized and die
Point of keratinization is about halfway to skin surface and marks boundary between hair root and shaft
Hair root – portion that anchors hair into skin
Hair shaft – hair part we see on the surface

34. Hair Shaft Structure (5-6)
Three layers of dead, keratinized cells
Cuticle (surface layer)
Made of an overlapping shingle-like layer of cells
Contains hard keratin, giving hair stiffness
Cortex – also contains hard keratin
Medulla
Makes up the core
Contains flexible soft keratin

35. Figure 5-5c Hair Follicles and Hairs.
Connective tissue sheath
Wall of hair follicle
Cuticle of hair
Cortex of hair
Medulla of hair C
This cross section through a hair
follicle was taken at the boundary
between the hair shaft and hair root.
Figure 5-5c Hair Follicles and Hairs.

36. Hair Growth (5-6) Hair growth cycle Grows for two to five years
Follicle becomes inactive for same time frame
When new growth cycle begins, follicle produces new hair
Old hair gets pushed to surface and shed

37. Functions of Hair (5-6) Protects the scalp from UV light
Provides insulation for the skull
Prevents entry of foreign particles into nose, eyes, and ears
Provides early-warning system to prevent injury due to sensory fibers at base of hair follicles
Expresses emotional state by hair “standing up” due to contraction of arrector pili muscle
Produces “goose bumps”

38. Hair Color (5-6)
Differences due to type and amount of melanin from melanocytes
Hair color varies from black to blond
Genetically determined and influenced by hormones and environmental factors
Pigment production declines with age causing gray or white hair

39. Exocrine Glands of the Skin (5-7)
Two types of exocrine glands in the integument
Sebaceous glands
Sweat glands
Figure 5-6 Sebaceous Glands and Their Relationship to Hair Follicles.

40. Sebaceous Glands (5-7) Also called oil glands
Discharge oily lipid secretion (sebum) into hair follicles through holocrine secretion (cell dies and detaches)
Sebum inhibits growth of bacteria, lubricates the hair, and conditions surrounding skin
Sebaceous follicles discharge sebum directly onto skin of face, back, chest, nipples, and external genitalia

41. Sebaceous Glands and Acne (5-7)
Sebaceous glands are sensitive to changes in concentrations of sex hormones
Secretions accelerate at puberty
Acne
Blocked sebaceous ducts causes inflammation and raised “pimple”

42. Sweat Glands (5-7) Also called sudoriferous glands Include two types
Apocrine
Merocrine
Figure 5-7 Sweat Glands.

43. Apocrine Sweat Glands (5-7)
Become active at puberty
Secrete into hair follicles in armpits, around nipples, and in pubic region
Secretion is sticky, cloudy, and potentially odorous
Portions of cell with secretions pinch off
Sweat is food source for bacteria on skin, increasing odor

44. Merocrine Sweat Glands (5-7)
Coiled tubular structure secretes watery perspiration directly onto surface of skin
Very numerous with high numbers on soles and palms
Sweat is 99 percent water with electrolytes, urea, and organic nutrients
Sodium chloride gives it the salty taste
Function is to cool body through evaporation

45. Modified Sweat Glands (5-7)
Mammary glands
Structurally related to apocrine sweat glands
Secrete milk
Ceruminous glands
Located in passageway of external ear
Secretions combine with sebaceous gland secretions to form cerumen, or earwax

46. Nails (5-8) Protect surfaces of tips of fingers and toes
Visible nail body
Made of dense, keratinized cells
Recessed beneath surrounding epithelium
Bordered by lateral nail folds
Nail bed
Deeper level of epidermis covered by nail body

47. Nail Structure (5-8) Nail root Lunula
Epithelial fold not visible from the surface
Site of nail production
Covered by the cuticle
Portion of the stratum corneum
Lunula
Pale crescent near nail root

48. Figure 5-8 The Structure of a Nail.

49. Repair of the Integument (5-9)
Skin regeneration occurs because:
Stem cells of epithelium and connective tissue undergo cell division
Replacing lost or damaged tissue
Four phases of skin regeneration
Inflammatory phase
Migratory phase
Proliferation phase
Scarring phase

50. Inflammatory Phase (5-9)
Mast cells released at bleeding injury site trigger inflammatory response
Result is increased blood flow to region and increased numbers of phagocytes
Figure 5-9 Repair of Injury to the Skin.

51. Migratory Phase (5-9) Blood clot or scab forms at surface
Stratum basale cells migrate along wound edges to replace missing cells
More phagocytes clear debris and pathogens
If wound covers extensive area or involves a region of thin skin:
Granulation tissue forms in deeper tissue
Combination of blood clot, fibroblasts, and extensive capillary network

52. Figure 5-9 Repair of Injury to the Skin.2
Migratory Phase
After several hours, a scab
has formed and cells of the
stratum basale are
migrating along the edges
of the wound. Phagocytic
cells are removing debris,
and more of these cells are
arriving with the enhanced
circulation in the area.
Clotting around the edges
of the affected area
partially isolates the region.
Migrating
epithelial
cells
Macrophages
and fibroblasts
Granulation
tissue
Figure 5-9 Repair of Injury to the Skin.

53. Proliferation Phase (5-9)
Deeper parts of the clot dissolve
Number of capillaries declines
Fibroblasts have formed extensive meshwork of collagen fibers
Figure 5-9 Repair of Injury to the Skin.

54. Scarring Phase (5-9) Scab is shed and epidermis is complete
Shallow depression marks injury site
Fibroblasts create fibrous, noncellular scar tissue to elevate epidermis
Degree of scar formation dependent on severity and location of injury and age of patient
Keloids are thickened areas of scar tissue covered by shiny, smooth epidermal surface

55. Figure 5-9 Repair of Injury to the Skin.
Figure 5-10 A Keloid.

56. Effects of Burns (5-9)
Burns result from exposure of skin to heat, radiation, electrical shock, or strong chemicals
Severity depends on depth into the tissues and the total area affected
Skin functions affected by burns
Fluid and electrolyte balance
Thermoregulation
Protection from infection

57. Classification by Depth of Burn (5-9)
Partial-thickness burns
First-degree burn
Only the epidermis is affected
Causes erythema or redness from inflammation
Example: sunburn
Second-degree burn
Entire epidermis and part of the dermis damaged
Causes blistering, pain, and swelling
Some scar tissue may form

58. Unnumbered Figure, Page 136-1 & 2
Partial-thickness Burns
Erythema
Erythema

59. Unnumbered Figure, Page 136-3
Full-thickness Burns

60. Effects of Aging on the Integument (5-10)
Skin injuries and infections are more common
Likely due to a thinning of the epidermis as stem cells become less active
Sensitivity of immune system is reduced
Mainly due to a decrease of macrophages residing in the skin
Muscles become weaker and bone strength decreases
Due to a decline in vitamin D3

61. Effects of Aging on the Integument (5-10)
Sensitivity to sun exposure increases
Due to lower amount of melanin production
Skin becomes dryer and often scaly
Due to reduction in glandular secretions
Hair thins and changes color
Due to low-functioning follicles and decreased melanocyte activity

62. Effects of Aging on the Integument (5-10)
Sagging and wrinkling of the skin occurs
Due to decrease in elastic network, more noticeable when skin has been exposed to a lot of sunlight
Ability to lose heat is reduced
Due to reduced dermal blood supply and less active sweat glands
Skin repairs take place more slowly
Due to slower stem cell division, increasing the threat of infection in cuts