1. Chapter 5: The Integumentary System

2. Size of the Integument
The integument is the largest system of the body:
16% of body weight
1.5 to 2 m2 in area

3. Parts of the Integument
The integument is made up of
2 parts:
cutaneous membrane (skin)
accessory structures

4. Parts of the Integumentary System
Figure 5–1

5. Parts of the Cutaneous Membrane
Outer epidermis:
superficial epithelium (epithelial tissues)
Inner dermis:
connective tissues

6. Accessory Structures Originate in the dermis
Extend through the epidermis to skin surface:
hair
nails
multicellular exocrine glands

7. Functions of Skin Protects underlying tissues and organs
Excretes salts, water, and organic wastes (glands)
Maintains body temperature (insulation and evaporation)

8. Functions of Skin Synthesizes vitamin D3 Stores lipids
Detects touch, pressure, pain, and temperature

9. What are the main structures and functions of the epidermis?

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

11. Organization of the Epidermis
Figure 5–2

12. Layers of the Epidermis
From basal lamina to free surface:
stratum germinativum
stratum spinosum
stratum granulosum
stratum lucidum
stratum corneum

13. Stratum Germinativum The “germinative layer”:
has many germinative (stem) cells or basal cells
is attached to basal lamina by hemidesmosomes
forms a strong bond between epidermis and dermis

14. Structures of Stratum Germinativum
Epidermal ridges (e.g., fingerprints)
Dermal papillae (tiny mounds):
increase the area of basal lamina
strengthen attachment between epidermis and dermis

15. Ridges and Ducts
Figure 5–4

16. Cells of Stratum Germinativum
Merkel cells:
found in hairless skin
respond to touch (trigger nervous system)
Melanocytes:
contain the pigment melanin
scattered throughout stratum germinativum

17. Stratum Spinosum The “spiny layer”:
produced by division of stratum germinosum
8–10 layers of keratinocytes bound by desmosomes
cells shrink until cytoskeletons stick out (spiny)

18. Cells of Stratum Spinosum
Continue to divide, increasing thickness of epithelium
Contain Langerhans cells, active in immune response

19. Stratum Granulosum The “grainy layer”
Stops dividing, starts producing:
keratin:
a tough, fibrous protein
makes up hair and nails
keratohyalin
dense granules
cross-link keratin fibers

20. Cells of Stratum Granulosum
Produce protein fibers
Dehydrate and die
Create tightly interlocked layer of keratin surrounded by keratohyalin

21. Stratum Lucidum The “clear layer”: found only in thick skin
covers stratum granulosum

22. Cells of Stratum Lucida
Flat
Dense
Filled with keratin

23. Stratum Corneum The “horn layer”: exposed surface of skin
15 to 30 layers of keratinized cells
water resistant
shed and replaced every 2 weeks

24. Keratinization
The formation of a layer of dead, protective cells filled with keratin
Occurs on all exposed skin surfaces except eyes

25. Skin Life Cycle
It takes 15–30 days for a cell to move from stratum germinosum to stratum corneum

26. What causes different skin colors?

27. Skin Color Skin color depends on: the pigments carotene and melanin
blood circulation (red cells)

28. Carotene Orange-yellow pigment Found in orange vegetables
Accumulates in epidermal cells and fatty tissues of the dermis
Can be converted to vitamin A

29. Melanin Yellow-brown or black pigment
Produced by melanocytes in stratum germinativum
Stored in transport vesicles (melanosomes)
Transferred to keratinocytes

30. Function of Melanocytes
Melanin protects skin from sun damage
Ultraviolet (UV) radiation:
causes DNA mutations and burns which lead to cancer and wrinkles
Skin color depends on melanin production and not the number of melanocytes

31. Melanocytes
Figure 5–5

32. Capillaries and Skin Color
Oxygenated red blood contributes to skin color:
blood vessels dilate from heat, skin reddens
blood flow decreases, skin pales

33. Cyanosis Bluish skin tint
Caused by severe reduction in blood flow or oxygenation

34. Illness and Skin Color Jaundice: Addison’s disease:
buildup of bile produced by liver
yellow color
Addison’s disease:
and other diseases of pituitary gland
skin darkening

35. Illness and Skin Color
Vitiglio:
loss of melanocytes
loss of color

36. Vitamin D Epidermal cells produce cholecalciferol (vitamin D3):
in the presence of UV radiation
Liver and kidneys convert vitamin D into calcitriol:
to aid absorption of calcium and phosphorus

37. Epidermal Growth Factor (EGF)
Is a powerful peptide growth factor
Is produced by glands (salivary and duodenum)
Is used in laboratories to grow skin grafts

38. Functions of EGF Promotes division of germinative cells
Accelerates keratin production
Stimulates epidermal repair
Stimulates glandular secretion

39. What are the structures and functions of the dermis?

40. The Dermis Is located between epidermis and subcutaneous layer
Anchors epidermal accessory structures (hair follicles, sweat glands)
Has 2 components:
outer papillary layer
deep reticular layer

41. The Papillary Layer Consists of areolar tissue
Contains smaller capillaries, lymphatics, and sensory neurons
Has dermal papillae projecting between epidermal ridges

42. The Reticular Layer Consists of dense irregular connective tissue
Contains larger blood vessels, lymph vessels, and nerve fibers
Contains collagen and elastic fibers
Contains connective tissue proper

43. Characteristics of Dermis
Strong, due to collagen fibers
Elastic, due to elastic fibers
Flexible (skin turgor)

44. Dermal Circulation
Figure 5–8

45. Arteries Cutaneous plexus: Papillary plexus:
a network of arteries along the reticular layer
Papillary plexus:
capillary network from small arteries in papillary layer

46. Veins Venous plexus: Contusion:
capillary return deep to the papillary plexus
Contusion:
damage to blood vessels resulting in “black and blue” bruising

47. Nerves Nerve fibers in skin control:
blood flow
gland secretions
sensory receptors
Tactile disks monitor Merkel cells

48. What are the structures and functions of the subcutaneous layer?

49. The Hypodermis The subcutaneous layer or hypodermis:
lies below the integument
stabilizes the skin
allows separate movement

50. Structure of the Hypodermis
The subcutaneous layer is:
made of elastic areolar and adipose tissues
connected to the reticular layer of integument by connective tissue fibers

51. Clinical Importance Subcutaneous layer:
has few capillaries and no vital organs
is the site of subcutaneous injections using hypodermic needles

52. Adipose Tissue Deposits of subcutaneous fat:
have distribution pattern determined by hormones
are reduced by cosmetic liposuction

53. Integumentary Accessory Structures
Hair, hair follicles, sebaceous glands, sweat glands, and nails:
are derived from embryonic epidermis
are located in dermis
project through the skin surface

54. What determines hair growth, texture, and color?

55. Location of Hair The human body is covered with hair, except: palms
soles
lips
portions of external genitalia

56. Functions of Hair Protects and insulates
Guards openings against particles and insects
Is sensitive to very light touch

57. The Hair Follicle Is located deep in dermis Produces nonliving hairs
Is wrapped in a dense connective-tissue sheath
Base is surrounded by sensory nerves (root hair plexus)

58. Structures of Hair and Follicles
Figure 5–9a

59. Accessory Structures of Hair
Arrector pili:
involuntary smooth muscle
causes hairs to stand up
produces “goose bumps”
Sebaceous glands:
lubricate the hair
control bacteria

60. Regions of the Hair Hair root: Hair shaft: lower part of the hair
attached to the integument
Hair shaft:
upper part of the hair
not attached to the integument

61. Inside the Follicle
Figure 5–9b

62. How Hair Grows Hair begins deep in the dermis:
the hair papilla contains capillaries and nerves
the hair bulb produces hair matrix

63. Hair Matrix A layer of dividing basal cells Produce hair structure
Push hair up and out of skin

64. Layers in a Hair Medulla: Cortex: Cuticle the central core
the middle layer
Cuticle
the surface layer

65. Structure of a Hair
Figure 5–9d

66. Keratin As hair is produced, it is keratinized:
medulla contains flexible soft keratin
cortex and cuticle contain stiff hard keratin

67. Layers in the Follicle Internal root sheath: External root sheath:
the inner layer
contacts the cuticle in lower hair root
External root sheath:
extends from skin surface to hair matrix
Glassy membrane:
a dense connective-tissue sheath
contacts connective tissues of dermis

68. Structures of a Follicle
Figure 5–9c

69. Hair Growth Cycle Growing hair: Club hair:
is firmly attached to matrix
Club hair:
is not growing
is attached to an inactive follicle

70. Hair Growth Cycle New hair growth cycle: follicle becomes active
produces new hair
club hair is shed

71. Types of Hairs Vellus hairs: Terminal hairs: soft, fine
cover body surface
Terminal hairs:
heavy, pigmented
head and eyebrows
other parts of body after puberty

72. Hair Color Produced by melanocytes at the hair papilla
Determined by genes

73. What are the skin glands and secretions?

74. Exocrine Glands Sebaceous glands (oil glands): Sweat glands:
holocrine glands
secrete sebum
Sweat glands:
merocrine glands
watery secretions

75. Types of Sebaceous Glands
Simple branched alveolar glands:
associated with hair follicles
Sebaceous follicles:
discharge directly onto skin surface

76. Sebaceous Glands
Figure 5–10

77. Sebum Contains lipids and other ingredients
Lubricates and protects the epidermis
Inhibits bacteria

78. What are the functions of sweat glands?

79. Types of Sweat Glands Apocrine: Merocrine:
found in armpits, around nipples, and groin
Merocrine:
widely distributed on body surface
especially on palms and soles

80. Apocrine Sweat Gland
Figure 5–11a

81. Apocrine Sweat Glands Merocrine secretions, not apocrine
Associated with hair follicles
Produce sticky, cloudy secretions
Break down and cause odors

82. Myoepithelial Cells
Squeeze apocrine gland secretions onto skin surface
In response to hormonal or nervous signals

83. Merocrine Sweat Glands
Also called eccrine glands:
coiled, tubular glands
discharge directly onto skin surface
sensible perspiration
water, salts, and organic compounds

84. Merocrine Sweat Gland
Figure 5–11b

85. Functions of Merocrine Sweat
Cools skin
Excretes water and electrolytes
Flushes microorganisms and harmful chemicals from skin

86. Other Integumentary Glands
Mammary glands:
produce milk
Ceruminous glands:
protect the eardrum
produce cerumen (earwax)

87. Control of Glands Autonomic nervous system: Merocrine sweat glands:
controls sebaceous and apocrine sweat glands
works simultaneously over entire body
Merocrine sweat glands:
are controlled independently
sweating occurs locally

88. Homeostasis Thermoregulation:
is the main function of sensible perspiration
works with cardiovascular system
regulates body temperature

89. Nail Functions Nails protect fingers and toes:
made of dead cells packed with keratin
metabolic disorders can change nail structure

90. Nail Production
Occurs in a deep epidermal fold near the bone called the nail root

91. Structure of a Nail
Figure 5–12

92. Structures of Nails Nail body: Lunula: the visible portion of the nail
covers the nail bed
Lunula:
the pale crescent at the base of the nail

93. Structures of Nails Sides of nails:
lie in lateral nail grooves
surrounded by lateral nail folds
Skin beneath the free edge of the nail:
is the hyponychium

94. Structures of Nails Visible nail emerges:
from the eponychium (cuticle)
at the tip of the proximal nail fold

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

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

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

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

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