1. Chapter 5: The Integumentary System

2. The structures and functions of the integumentary system.

3. Structure of the Integument
16% of body mass
Composed of:
Cutaneous Membrane:
Epidermis– Superficial epithelium
Dermis – underlying CT with blood supply
Accessory Structures: originate in dermis
Hair
Nails
Exocrine Glands

4. Parts of the Integumentary System
Figure 5–1

5. Functions of the Integument
Protects underlying tissues from infection, exposure and dehydration
Excretes salts, water, and organic waste
Maintains normal body temp: conserve and radiate heat
Synthesizes Vitamin D3 for calcium metabolism
Stores Nutrients and Fat
Sensory detection:
- touch, pressure, pain, and temp.

6. Connections Circulatory system: Nervous system:
blood vessels in the dermis
Nervous system:
sensory receptors for pain, touch, and temperature

7. The main structures and functions of the epidermis.

8. Epidermis Avascular stratified squamous epithelium
Nutrients and oxygen diffuse from capillaries in the dermis

9. Cells of the Epidermis Keratinocytes: Thin Skin: Hairy
contain large amounts of keratin
the most abundant cells in the epidermis
Thin Skin: Hairy
Covers most of the body
Has 4 layers of keratinocytes
Thick Skin: No Hair
Covers the palms of the hands and soles of the feet
Has 5 layers of keratinocytes

10. Structures of the Epidermis
The 5 strata of keratinocytes in thick skin
Figure 5–3

11. Layers of the Epidermis
From basal lamina to free surface:
stratum germinativum
stratum spinosum
stratum granulosum
stratum lucidum
stratum corneum
Transit from stratum basale to stratum corneum:
15-30 days
Duration at stratum corneum:
7-14 days
Complete turnover ever days

12. 1. Stratum Germinativum/Basale
The “germinative layer”: Single Layer
has many germinative (stem) cells or basal cells
is attached to basal lamina by hemidesmosomes
forms a strong bond between epidermis and dermis
Cells:
basal/germinative cells (stem cells), melanocytes (melanin), some Merkel cells in hairless skin (touch receptors)
Structure:
Epidermal ridges (e.g., fingerprints)
Dermal papillae (tiny mounds):
increase the area of basal lamina
strengthen attachment between epidermis and dermis

13. Layers of the Epidermis
2. Stratum Spinosum:
8-10 layers keratinocytes attached by desmosomes
some cells can divide
some Langerhans cells present (immune response)
3. Stratum Granulosum:
3-5 layers keratinocytes producing keratin fibers, keratohyaline granules, and lamellated granules
Keratin = basic structural component of hair and nails
Keratohyaline = Promotes dehydration of the cells and cross-linking of keratin fibers
No cell division, nuclei and organelles being to disintegrate

14. Layers of the Epidermis
4. Stratum Lucidum:
- thick skin only, flat packed keratin filled keratinocytes
5. Stratum Corneum:
15-30 layers dead keratinocytes that have been keratinized (cornified)
Soft keratin fibers glued in paralled arrays by keratohyaline
Extracellular space filled with glycolipids from lamellated granules
Cornified = water and chemical resistant
not water proof since interstitial fluid can evaporate

15. Ridges and Ducts The corrugated border between dermis and
epidermis helps bond the epidermis and
dermis
- increased surface area for attachment
In thick skin epidermal ridges show on the
surface as fingerprints:
Function – enhance gripping
Figure 5–4

16. stratum germinativum stratum spinosum stratum corneum
Dandruff is caused by excessive shedding of cells from the outer layer of skin in the scalp. Thus dandruff is composed of cells from which epidermal layer?
stratum germinativum
stratum spinosum
stratum corneum
stratum granulosum

17. A splinter that penetrates to the third layer of the epidermis of the palm is lodged in which layer?
1. stratum lucidum
2. stratum germinativum
3. stratum spinosum
4. stratum granulosum

18. 1. Yes, because the dermal papillae die if exposed.
Some criminals sand the tips of their fingers so as not to leave recognizable fingerprints. Would this practice permanently remove fingerprints? Why or why not?
1. Yes, because the dermal papillae die if exposed.
2. No, because the ridge patterns regenerate.
3. Yes, because the stratum germinativum thickens hiding ridge patterns.
4. No, because different ridge patterns will appear with re-growth.

19. Characteristics of Skin
Skin is water resistant but not water proof:
Insensible perspiration:
Water from interstitial fluids evaporate
Water loss can not be seen or felt
water loss through skin: ~500ml (1 pint)/day
More if damaged (e.g. burn)
Sensible perspiration:
Aware of water loss
Produced by active sweat glands

20. Characteristics of Skin
Callus:
Thickening of skin, due to friction
Blister:
Separation of epidermal layers or epidermis form dermis
space fills with interstitial fluid

21. Skin Color
Pigment based: epidermal pigments and blood pigments contribute to the color
Epidermal Pigmentation
Dermal Circulation

22. Skin Color Epidermal Pigmentation
A. Carotene: yellow-orange, from diet
- converted into Vitamin A
- localized to epithelium
- functions in normal maintenance of epithelia and photoreceptors
- excess accumulates in stratum
corneum
B. Melanin: Brown, from melanocytes
- for UV protection

23. 1. Epidermal Pigmentation
Melanocytes: in stratum basale
Synthesize melanin from tyrosine (amino acid)
Packaged in melanosomes
Melanosomes are transferred to cytoplasm of keratinocytes
Cluster around top side of nucleus
Eventually digested by lysosomes
Everyone has ~1000 melanocytes/mm2
Pale People: small melansomes, present on in stratum basale and spinosum
Dark People: larger, greater number of melansomes, retained up through stratum granulosum

24. 1. Epidermal Pigmentation
Freckles:
Overproduction of melanin form single melanocytes
UV exposure:
Some needed for Vitamin D3 production
Excess = damage (DNA mutation)
Harm Fibroblasts  impaired maintenance of the dermis resulting in altered CT structures
Wrinkles
Chromosomal damage of Epidermal cells or melanocytes  cancer
Squamous cell carcinoma
Melanoma

25. Skin 2. Dermal Circulation: hemoglobin pigment - Oxygenated blood:
- red color, hemoglobin in RBCs, through skin=pink
- Vasodilation  skin looks more red
- Vasoconstriction  skin looks more pale
- Cyanosis:
- low oxygen, blood deep purple, skin appears
blue/purple
- results form low temp., heart failure, asthma

26. Abnormal Skin Color Jaundice: Addison’s Disease: Albinism: Vitiligo:
Liver fails to excrete bile
Bile accumulates in skin = yellow
Addison’s Disease:
Pituitary secretes excess adrenocorticotropic hormone, stimulates melanoctyes, excess melanin, bronzing
Albinism:
Genetic mutation in melanin biosynthesis pathway
Lack pigmentation in skin, hair and eyes
Vitiligo:
Autoimmune disease  destruction of melanocytes

27. Vitamin D3 Production Cells of stratum spinosum and basale:
UV energy + cholesterol = Vitamin D3
Vitamin D3:
used by kidney to synthesize the hormone calcitriol
Calcitriol:
necessary to signal small intestine to absorb calcium
No VitD  no calcitriol  no calcium
absorption  weak bones

28. KEY CONCEPT The epidermis:
is a multilayered, flexible, self-repairing barrier
prevents fluid loss
protects from UV radiation
produces vitamin D3
resists abrasion, chemicals, and pathogens

29. Why does exposure to sunlight or sunlamps darken skin?
1. UV stimulates melanocytes.
2. Melanin darkens in sunlight.
3. Stratum corneum cells appear brown.
4. Keratin appears brown when heated.

30. Why does the skin of a fair-skinned person appear red during exercise in hot weather?
1. Sunlight stimulates erythrocyte production in skin.
2. Blood is diverted to the superficial dermis to eliminate heat.
3. Sunlight bleaches fair skin, allowing blood to be seen.
4. Heat stimulates cutaneous blood vessels, causing leaks.

31. 1. UV light prevents calcium deposition in bones.
In some cultures, women must be covered completely, except for their eyes, when they go outside. Explain why these women exhibit a high incidence of problems with their bones.
1. UV light prevents calcium deposition in bones.
2. Melanin production is necessary for bone growth.
3. Cloth prevents oxygen from diffusing into skin and bones.
4. UV light is necessary to produce the hormone cholecalciferol (vitamin D3).

32. The structures and functions of the dermis.

33. The Dermis Is located between epidermis and subcutaneous layer
Anchors epidermal accessory structures
hair follicles, sweat glands
Contains:
All cells of CT proper, accessory organs of integument, blood vessels, lymphatic vessels, nerves, and sensory receptors
Has 2 components:
outer papillary layer
deep reticular layer

34. Dermis Papillary layer: Reticular Layer: Thin (20%) Consists:
Areolar CT
Comprise dermal papillae
Capillaries, lymphatics, and
sensory neurons
Function: feed epidermis
Reticular Layer:
Thick (80%)
Dense irregular CT
Elastic and Collagen fibers
Function: provide strength and flexibility

35. Dermis Collagen fibers from reticular layer
blend into papillary and subcutaneous layers to attach integument to body
Wrinkles = Dermis stretched beyond its elastic capacity
collagen fibers damaged
Stretch marks = collagen and elastic fibers torn
Thickened tissue resulting from pregnancy, weight gain, muscle gain
Collagen and Elastin fibers arranged in parallel bundles:
aligned to resist the expected direction of force = lines of cleavage
Cuts parallel to lines of cleavage will heal faster and with less scar than those perpendicular

36. Lines of Cleavage
Figure 5–7

37. Dermis Dermis highly vascularized: Contusion:
must “feed” itself and epidermis above
Contusion:
bruise, trauma that ruptures blood vessels but does not break skin, blood pools in dermis and must be removed by phagocytes (slow process)

38. Dermatitis An inflammation of the papillary layer Caused by
infection, radiation, mechanical irritation, or chemicals (e.g., poison ivy)
Characterized by
itch or pain
Characteristics
Strong, due to collagen fibers
Elastic, due to elastic fibers
Flexible

39. Skin Damage
Sagging and wrinkles (reduced skin elasticity) are caused by:
dehydration
age
hormonal changes
UV exposure

40. Sensory Perception in Integument
Skin highly innervated for sensory perception, mostly in dermis
Merkel Cells
Free Nerve Endings
Meissner’s Corpuscles
Pacinian/Lamellated Corpuscles

41. Sensory Perception in Integument
Merkel cells: deep layers of epidermis
- superficial touch
Free Nerve Endings: superficial dermis
- pain and temperature
Meissner’s Corpuscles: superficial dermis
- light tough
Pacinian/Lamellated Corpuscles: deep dermis
- pressure and vibrations

42. Thin Skin
Thick Skin

43. Where are the capillaries and sensory neurons that supply the epidermis located?
1. reticular layer of the dermis
2. epidermis
3. papillary layer of the dermis
4. hypodermic layer

44. What accounts for the ability of the dermis to undergo repeated stretching?
1. elastic fibers and skin turgor resilience
2. reticular fibers and fluids
3. adipocytes and elastic fibers
4. sebaceous gland secretions

45. The structures and functions of the subcutaneous layer.

46. The Hypodermis The subcutaneous layer or hypodermis:
lies below the integument
Not part of cutaneous membrane
Stabilizes position of skin while permitting independent movement of skin and muscles

47. Subcutaneous Layer (aka Hypodermis)
Areolar and adipose CT
Tightly interwoven with reticular layer of dermis
Children: even layer of adipose
Puberty: Adipose shifts
Male: neck, arms, abdomen, lower back
Female: breast, buttocks, hips, thighs
No vital organs: safe for “SubQ” injection, vascular for quick absorption

48. KEY CONCEPT The dermis:
provides mechanical strength, flexibility and protection
is highly vascularized
contains many types of sensory receptors

49. Integumentary Accessory Structures
Hair and hair follicles
Sebaceous glands
Sweat glands
Nails
Accessory Structures:
are derived from embryonic epidermis
are located in dermis
project through the skin surface

50. Hair Human body: Everywhere except:
~2.5 million hairs, 75% on body
Everywhere except:
palms, soles, lips, and certain genitalia
Hair itself is dead, but is derived from live epidermal tissue
Hair and Hair Follicle Structure

51. Hair growth, texture, and color.

52. Functions of Hair Function: Structure of Hair Follicle:
Protects and insulates
Guards openings against particles and insects
Is sensitive to very light touch
Structure of Hair Follicle:
Hair Follicle
Glassy membrane
Hair bulb
Hair papilla
Hair Matrix
Structure of Hair:
Hair root
Hair shaft

53. The Hair Follicle Hair is produced in organs called hair follicles
Tube of stratified squamous epithelium anchored in dermis
Surrounds, supports, and produces hair
Two layers:
Internal Root Sheath:
contacts hair
External Root Sheath:
contacts glassy membrane

54. Hair Follicle Structure
Glassy membrane
Thick basal lamina between epithelial follicle and connective tissue dermis
Hair bulb consist of epithelial cells
Expanded base of follicle that surrounds papilla and matrix
Responsible for producing hair by forming the hair matrix layer
Hair Matrix
Dividing epithelial/basal cells and melanocytes above papilla that form new hair
Cells gradually push toward the surface
Hair papilla
CT at base of bulb, contains capillaries and nerves
Supports matrix

55. Hair Structure Hair Root: Hair Shaft: Embedded in dermis
Not yet fully formed
Contains live cells
Hair Shaft:
Pokes through epidermis
Fully organized dead hair
Three layers
Cuticle: outermost, overlapping dead keratinized cells form shiny surface
Cortex: middle layer, dead cells contain hard keratin to provide stiffness
Medulla: core, dead cells contain soft keratin and air to provide flexible

56. Hair Structure Shape of the Shaft determines feel:
Flattened shaft = kinky hair
Oval shaft = silky and wavy hair
Round shaft = straight and often stiff hair
Two types of Hair produced:
Vellus Hairs = “peach fuzz”
Lacks medulla
Covers body, at puberty hormones can trigger switch to terminal hairs
Vellus hairs present at the armpits, pubic area, and limbs switch to terminal hairs in response to circulating sex hormones
Terminal Hairs = head, eyebrows and eyelashes
- Thick, coarse, pigmented

57. Hair Color red: iron added
Range yellow to black due to melanin from melanocytes in hair matrix
Melanin stored in cortex and medulla
With age, melanin declines, air pockets in medulla increase = gray or white hair

58. Hair Growth Hair in the Scalp: During hair growth:
Grows for 2-5 yrs, at a rate of 0.33 mm per day
During hair growth:
Cells of the hair root absorb nutrients and incorporate them into the hair structure  History of Exposure
Result  clipping or collecting hair for analysis is helpful in diagnosing several disorders (ex. Heavy Metals, nucleus = DNA)
The root is firmly attached to the matrix of the follicle
At the end of growth:
The follicle becomes inactive  termed club hair
Follicle gets smaller
Connections between the hair matrix and the club hair root breaks down.
Another cycle begins:
Follicle produces a new hair
The old club hair is pushed to the surface and shed

59. Hair Growth ~0.33mm/day, not continuous: cycle of growth and rest
Active phase:
- new hair added to hair root by dividing cells of hair matrix (weeks – years)
Regressive phase:
- cells of hair matrix stop dividing
- hair root and hair papilla separate loose hair = club hair
Resting phase:
- cells of hair matrix and hair follicle remain inactive (1-3 months)
New Active Phase Begins
Hair length differences = difference in time spent in active phase:
eyebrows = few months
head – many years

60. Shedding of the hair occurs only after the next growth cycle begins and a new hair shaft begins to emerge.
On average hairs are shed every day.
The percentage of follicles in the resting phase will vary at any time depending on the body area.
Factors that can affect the hair growth cycle and cause temporary or permanent hair loss (alopecia) including:
medication, radiation, chemotherapy, exposure to chemicals, hormonal and nutritional factors, thyroid disease, generalized or local skin disease, stress, and high fevers.

61. Hair Growth Alopecia: Male Pattern Baldness: Hair Removal:
Shift from terminal hair to vellus hair, thinning/balding, some degree expected with age
Male Pattern Baldness:
Genetic alopecia, early age onset
Caused by a shift from terminal to vellus hair production due to a change in the level of sex hormones circulating in the blood
Treatment:
Aimed at converting vellus hairs to terminal hairs
Hair Removal:
Difficult to achieve permanent result
Any remaining matrix cells can regenerate all hair follicle structures

62. Hair Function Head: Nostrils, Ear canals, Eyelashes: Body Hair:
UV protection
Cushion from trauma
Insulation
Nostrils, Ear canals, Eyelashes:
Prevent entry of foreign material
Body Hair:
sensory detection

63. Hair Function: Sensory Detection
Root hair plexus:
Sensory nerves at base of hair follicle that detect slight movement of hair
Arrector pili muscle:
Attached to every hair follicle
Contract to stand hair perpendicular to skin surface
Goose bumps
Smooth muscle: involuntary

64. What happens when the arrector pili muscle contracts?
1. Sebum is released.
2. Goose bumps are evident.
3. Sweat is produced.
4. Blood flow is increased.

65. 3. Only in areas where the deep dermis was destroyed.
Once a burn on the forearm that destroys the epidermis, and extensive areas of the deep dermis heals, will hair grow again in the affected area?
1. Yes.
2. No.
3. Only in areas where the deep dermis was destroyed.
4. Only in areas where the epidermis and deep dermis were not destroyed.

66. The skin glands and secretions.

67. Exocrine Glands Sebaceous glands (oil glands):
holocrine glands (which destroys gland cells)
secrete sebum
Sudoriferous Glands/Sweat Glands
A. Merocrine/Eccrine sudoriferous glands
B. Apocrine sudoriferous/sweat gland
Sweat glands:
merocrine glands
watery secretions

68. Integumentary Glands All are exocrine glands Sebaceous glands
Secrete product onto skin surface via a duct
Sebaceous glands
Holocrine secretion
Secrete sebum into hair follicle
Sebum = lipids + cholesterol + proteins + electrolytes
Function:
Lubricate and protect keratin
Prevent evaporation
Inhibit bacterial growth
Sebaceous glands active in fetus, then off until puberty, and then back on for the whole adult life
Acne = Inflammation of a sebaceous gland,
* Usually due to bacterial infection

69. Integumentary Glands 2. Sudoriferous Glands/Sweat Glands
A. Merocrine/Eccrine sudoriferous glands
- 2 to 5 million all over body
- produce sensible perspiration:
- 99% water
- electrolytes + organic nutrients
+ antibodies + antimicrobial agents
+ organic waters
- merocrine secretion
- secretion via exocytosis of vesicles
- small coiled tubular glands
- located in superficial dermis
- open directly on surface of skin
- secrete in response to high temp. or stress

70. Functions of Sensible Perspiration
Evaporation cooling of surface of skin to reduce body temp.
Excrete waste electrolytes and drugs
Protection:
Prevent adherence of microbes: antibodies
Physically wash off microbes
Antimicrobial agents of kill microbes
Dermiciden (antibiotic)

71. Integumentary Glands B. Apocrine sudoriferous/sweat gland
2. Sudoriferous Glands/Sweat Glands
B. Apocrine sudoriferous/sweat gland
- merocrine secretion
- armpits, nipples, groin
- secrete into hair follicle
- secretion is stick and cloudy:
- sensible perspiration + protein + lipids
- microbes eat it  wastes = body odor
- glands deep in dermis
- Surrounded by myoepithelial cells: myo = muscle
- contraction of cells in response to sympathetic nervous system
stimulation causes discharge of secretion
- Active only after puberty
Special Apocrine Sweat Glands:
1. Mammary Glands:
- Located in female breast & Secrete milk during lactation
2. Ceruminous Glands:
- Located in external ear canal & Secrete cerumen (earwax)

72. Integumentary Gland Control
Merocrine sudoriferous glands:
can be turned on and off in localized regions in response to temperature or emotions
Sebaceous and apocrine sudoriferous glands:
Autonomic nervous system controls the activation and deactivation of these glands therefore they affect all the glands
are either all on (body wide) or all off
no local control

73. What are the functions of sebaceous secretions?
1. inhibits the growth of bacteria
2. lubricates and conditions the surrounding skin
3. lubricates and protects the keratin of the hair shaft
4. all of the above

74. Deodorants are used to mask the effects of secretions from which type of skin gland?
1. ceruminous glands
2. apocrine sweat glands
3. merocrine sweat glands
4. mammary glands

75. Which type of skin glands are most affected by the hormonal changes that occur during puberty?
1. ceruminous glands
2. sebaceous glands
3. apocrine sweat glands
4. merocrine sweat glands

76. The structure of nails.

77. Nails Scale like projections on dorsal surface of distal digits
Function:
protect tips from mechanical stress, assist in gripping
Consists of dead cells containing hard keratin
New nail formed at nail root
Cuticle = stratum corneum
Nail growth is continuous

78. How injured skin responds and repair itself.

79. Injury and Repair
Integument can function independent of nervous and endocrine systems to maintain own homeostasis
Mesenchymal cells of dermis can regenerate connective tissue
Germinative cells (basal cells) of epidermis can regenerate tissue

80. Repair of Localized Injuries to the Skin: Step 1
Bleeding occurs
Mast cells trigger inflammatory response
Figure 5–13 (Step 1)

81. Repair of Localized Injuries to the Skin: Step 2
A scab stabilizes and protects the area
Figure 5–13 (Step 2)

82. The Inflammatory Response
Germinative cells migrate around the wound
Macrophages clean the area
Fibroblasts and endothelial cells move in, producing granulation tissue

83. Repair of Localized Injuries to the Skin: Step 3
Fibroblasts produce scar tissue
Inflammation decreases, clot disintegrates
Figure 5–13 (Step 3)

84. Repair of Localized Injuries to the Skin: Step 4
Fibroblasts strengthen scar tissue
A raised keloid forms
Figure 5–13 (Step 4)

85. Injury and Repair Repair may end up like original tissue or keloid
Keloid = thick area of scar tissue covered by smooth epidermis
Burns:
First degree burn: heals on own
Damage to surface of epidermis
Second degree burn: heals on own
Damage to epidermis and superficial dermis
Third degree burn: Requires skin grafts or
“living bandages”
Damage to whole cutaneous layer (epidermis, dermis, accessory structures), granulation tissue cannot form thus no healing

86. Burns If burn > 20% of body can kill It affects:
Fluid and electrolyte
balance
Thermoregulation
Protection from
pathogens

87. What do you call the combination of fibrin clots, fibroblasts, and the extensive network of capillaries in healing tissue?
1. granulation tissue
2. scar
3. scab
4. callus

88. Why can skin regenerate effectively, even after considerable damage?
1. Stratum germinativum persists deep within the body.
2. Stem cells persist in all components of the skin.
3. Hypodermis will transform into epidermis and dermis.
4. Surrounding skin spreads and fills in damaged area.

89. The effects of aging on the skin.

90. Age Related Changes Stem cell activity declines:
Skin thin, repair is difficult
Langerhans cells decrease:
- Reduced immune response
Vitamin D3 production declines:
Calcium absorption declines  brittle bones
Glandular activity declines:
- skin dry, body can overheat
Bloody supply to dermis declines:
- tend to feel cold
Hair follicles die or produce thinner hair:
- terminal  vellus
Dermis thins and becomes less elastic  wrinkles
Sex characteristics fade:
- Fat deposits spread out, hair patterns change

91. 1. Blood supply to the dermis is reduced.
Older individuals do not tolerate the summer heat as well as they did when they were young, and they are more prone to heat-related illness. What accounts for these changes?
1. Blood supply to the dermis is reduced.
2. Glandular activity declines.
3. Melanocyte activity declines.
4. All of the above.

92. The integumentary system work with other systems.

93. Importance of the Integumentary System
Protects and interacts with all organ systems
Changes in skin appearance are used to diagnose disorders in other systems

94. Interactions with the Integumentary System
Figure 5–15

95. SUMMARY Division of: Layers of the epidermis:
integument into epidermis and dermis
epidermis into thin skin and thick skin
Layers of the epidermis:
stratum germinosum
stratum spinosum
stratum lucidum
stratum corneum
Roles of epidermal ridges and dermal papillae
Functions of specialized cells:
Langerhans cells & Merkel cells

96. SUMMARY Skin pigments: Metabolic functions of epidermis:
Carotene & Melanin
Metabolic functions of epidermis:
vitamin D3 &epidermal growth factor
Divisions of the dermis:
papillary layer
reticular layer
Mobility of the dermis:
stretch marks & lines of cleavage
Blood supply of the dermis:
cutaneous plexus
papillary plexus

97. SUMMARY Role of the subcutaneous layer
Structure of hair and hair follicles
Glands of the skin:
sebaceous
sweat
Ceruminous
Structure of nails
Processes of inflammation and regeneration
Effects of aging on the integument