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1

Integumentary System

components

consists of the skin and its accessory organs
–hair, nails, and cutaneous glands

2

dermatology

scientific study and medical treatment of the integumentary system

3

consists of two layers:

–epidermis–stratified squamous epithelium
–dermis–connective tissue layer

4

hypodermis

another connective tissue layer below the dermis

5

thick skin

on palms and sole, and corresponding surfaces on fingers and toes

6

thin skin

covers rest of the body

7

Functions of the Skin

7

resistance to trauma and infection
other barrier functions
vitamin D synthesis
sensation
thermoregulation
nonverbal communication
transdermal absorption

8

epidermis

keratinized stratified squamous epithelium
–lacks blood vessels
–depends on the diffusion of nutrients from underlying connective tissue
–sparse nerve endings for touch and pain

9

five types of cells of the epidermis

stem cells
keratinocytes
melanocytes
tactile (merkel) cells
dendritic (langerhans) cells

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stem cells

•undifferentiated cells that give rise to keratinocytes
•in deepest layer of epidermis (stratum basale)

11

melanocytes

•occur only in stratum basale

12

tactile (merkel) cells

•in basal layer of epidermis
•touch receptor cells associated with dermal nerve fibers

13

dendritic (langerhans) cells

•macrophages originating in bone marrow that guard against pathogens
•found in stratum spinosum and granulosum

14

Stratum Basale

a single layer of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane
–melanocytes and tactile cells are scattered among the stem cells and keratinocytes
•stem cells of stratum basale divide

15

Stratum Spinosum

•consists of several layers of keratinocytes
•thickest stratum in most skin
•deepest cells remain capable of mitosis
–cease dividing as they are pushed upward
–higher up in this stratum, the flatter the cells appear
•dendritic cells found throughout this stratum

16

Stratum Granulosum

•consists of 3 to 5 layers flat keratinocytes
•contain coarse dark-staining keratohyalin granules
membrane-coating vesicles release lipid mixture that spreads out over cell surface and waterproofs it

17

Stratum Lucidum

•seen only in thick skin
•thin translucent zone superficial to stratum granulosum

18

Stratum Corneum

•up to 30 layers of dead, scaly, keratinized cells
•form durable surface layer
–surface cells flake off (exfoliate)
•resistant to abrasion, penetration, and water loss

19

Epidermal Water Barrier

forms between stratum granulosum and stratum spinosum
•consists of:
–lipids secreted by keratinocytes
–tight junctions between keratinocytes
–thick layer of insoluble protein on the inner surfaces of the keratinocyte plasma membranes

20

Dermis

connective tissue layer beneath the epidermis
•composed mainly of collagen with elastic fibers, reticular fibers, and fibroblasts
•well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings

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piloerector muscles)

associated with hair follicles
–contract in response to stimuli, such as cold, fear, and touch –goose bumps

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Dermis

2 layers

reticular layer

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reticular layer

deeper and much thicker layer of dermis
–consists of dense, irregular connective tissue

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papillary layer

superficial zone of dermis
–thin zone of areolar tissue in and near the dermal papilla
–allows for mobility of leukocytes and other defense cells should epidermis become broken
–rich in small blood vessels

25

dermal papillae

upward fingerlike extensions of the dermis
–friction ridges on fingertips that leave fingerprints

26

stretch marks (striae)

tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity

27

Hypodermis

•subcutaneous tissue
•more areolar and adipose than dermis
•pads body
•binds skin to underlying tissues
•drugs introduced by injection
–highly vascular& absorbs them quickly
•subcutaneous fat

28

melanin

most significant factor in skin color
–produced by melanocytes
–accumulate in the keratinocytes of stratum basale and stratum spinosum
•people of different skin colors have the same number of melanocytes

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eumelanin

brownish black

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pheomelanin

a reddish yellow sulfur-containing pigment

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amount of melanin also varies with exposure to

exposure to ultraviolet (UV) rays of sunlight

32

Other Factors in Skin Color

•hemoglobin -red pigment of red blood cells
–adds reddish to pinkish hue to skin
•carotene -yellow pigment acquired from egg yolks and yellow/orange vegetables
–concentrates in stratum corneum and subcutaneous fat

33

cyanosis

blueness of the skin from deficiency of oxygen in the circulating blood

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erythema

abnormal redness of the skin due to dilated cutaneous vessels

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pallor

pale or ashen color when there is so little blood flow through the skin that the white color of dermal collagen shows through

36

albinism

genetic lack of melanin that results in white hair, pale skin, and pink eyes

37

jaundice

yellowing of skin and sclera due to excess of bilirubin in blood

38

hematoma

–(bruise) mass of clotted blood showing through skin

39

friction ridges

the markings on the fingertips that leave oily fingerprints on surfaces we touch

40

flexion lines

(flexion creases) –lines on the flexor surfaces of the digits, palms, wrists, elbows

41

freckles

freckles are flat, melanized patches

42

moles

are elevated melanized patches often with hair

43

hemangiomas

(birthmarks) –patches of discolored skin caused by benign tumors of dermal blood capillaries

–capillary , cavernous , port-wine stain

44

accessory organs

hair, nails, and cutaneous glands are accessory organs of the skin

45

soft keratin

makes up stratum corneum of skin

46

hard keratin

makes up hair and nails

47

pilus

another name for hair

48

hair

a slender filament of keratinized cells that grows from an oblique tube in the skin called a hair follicle

49

Types of Human Hair

lanugo
vellus–
terminal

50

lanugo

fine, downy, unpigmented hair that appears on the fetus in the last three months of development

51

vellus–

fine, pale hair that replaces lanugo by time of birth
•two-thirds of the hair of women
•one-tenth of the hair of men
•all of hair of children except eyebrows, eyelashes, and hair of the scalp

52

terminal

longer, coarser, and usually more heavily pigmented
•forms eyebrows, eyelashes, and the hair of the scalp
•after puberty, forms the axillary and pubic hair
•male facial hair and some of the hair on the trunk and limbs

53

Hair is divisible into three zones along its length

bulb
root

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bulb

a swelling at the base where hair originates in dermis or hypodermis
•only living hair cells are in or near bulb

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root

the remainder of the hair in the follicle

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shaft

the portion above the skin surface

57

dermal papilla

bud of vascular connective tissue encased by bulb
–provides

58

hair matrix

region of mitotically active cells immediately above papilla
–hair’s growth center

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three layers of the hair in cross-section from inside out

medulla
cortex

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medulla

•core of loosely arranged cells and air spaces

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cortex

•constitutes the bulk of the hair
•consists of several layers of elongated keratinized cells

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cuticle

composed of multiple layers of very thin, scaly cells that overlap each other
•free edges directed upward Hair

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follicle

diagonal tube that dips deeply into dermis and may extend into hypodermis

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epithelial root sheath

•extension of the epidermis
•lies immediately adjacent to hair root

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connective tissue root sheath

•derived from dermis
•surrounds epithelial root sheath

66

hair receptors

–nerve fibers that entwine each follicle
–respond to hair movement

67

piloerector muscle

–bundles of smooth muscle cells
–extends from dermal collagen to connective tissue root sheath
–goose bumps

68

hair cycle –
consists of three developmental stages

anagen

69

anagen

growth stage -90% of scalp follicles at any given time

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catagen

degenerative stage -mitosis in the hair matrix ceases and sheath cells below the bulge die

71

telogen

resting stage -when papilla reaches the bulge

72

club hair

may fall out during catagen or telogen
–or pushed out by new hair in the next anagen phase

73

hair growth

scalp hairs grow at a rate of 1 mm per 3 days

74

alopecia

thinning of the hair or baldness

75

pattern baldness

the condition in which hair loss from specific regions of the scalp rather than thinning uniformly

76

hirsutism

excessive or undesirable hairiness in areas that are not usually hairy

77

Functions of Hair

most hair on trunk and limbs is vestigial
•hair receptors alert us of parasites crawling on skin
•scalp helps retain heat
•scalp protects against sunburn

78

guard hairs

(vibrissae) -guard nostrils and ear canals
•eyelashes and eyebrows

79

fingernails and toenails

clear, hard derivatives of the stratum corneum
•composed of very thin, dead cells packed with hard keratin

80

nail plate

hard part of the nail
–free edge –overhangs the finger tip
–nail body –visible attached part of nail
–nail root –extends proximally under overlying skin

81

nail fold –

surrounding skin rising a bit above the nail

82

nail groove

separates nail fold from nail plate

83

nail bed

skin underlying the nail plate

84

hyponychium

epidermis of the nail bed

85

nail matrix

growth zone of thickened stratum basale at the proximal end of nail
–mitosis here accounts for nail growth

86

lunule

an opaque white crescent at proximal end of nail

87

eponychium

(cuticle) –narrow zone of dead skin

88

the skin has five types of glands-

-merocrine sweat glands
-apocrine sweat glands
-sebaceous glands-
ceruminous glands
-mammary glands

89

merocrine

(eccrine) sweat glands
•most numerous skin glands -3 to 4 million in adult skin
•are simple tubular glands
•watery perspiration that helps cool the body

90

apocrine sweat glands

•occur in groin, anal region, axilla, areola, bearded area in mature males
•ducts lead to nearby hair follicles
•produce sweat that is thicker, milky, and contains fatty acids
•scent glands that respond to stress and sexual stimulation
•develop at puberty

91

pheromones

chemicals that influence the physiology of behavior of other members of the species

92

bromhidrosis

disagreeable body odor produced by bacterial action on fatty acids

93

sweat

begins as a protein-free filtrate of blood plasma produced by deep secretory portion of gland
on average, 99% water, with pH range of 4 to 6

94

acid mantle

inhibits bacterial growth

95

insensible perspiration

500 ml per day
•does not produce visible wetness of skin

96

diaphoresis

sweating with wetness of the skin
•exercise –may lose one liter of sweat per hour

97

Sebaceous Glands

•sebum–oily secretion produced by sebaceous glands
•flask-shaped glands with short ducts opening into hair follicle
•keeps skin and hair from becoming dry, brittle, and cracked

98

holocrine gland

secretion consists of broken-down cells
–replaced by mitosis at base of gland

99

lanolin

sheep sebum

100

Ceruminous Glands

found only in external ear canal
•their secretion combines with sebum and dead epithelial cells to form earwax (cerumen)
•simple, coiled tubular glands with ducts that lead to skin surface

101

Mammary Glands

milk-producing glands that develop only during pregnancy and lactation
–modified apocrine sweat gland
–richer secretion released by ducts opening into the nipple

102

mammary ridges or milk lines

–two rows of mammary glands in most mammals
–primates kept only anterior most glands

103

polythelia

additional nipples

104

skin cancer

induced by the ultraviolet rays of the sun
–most often on the head and neck
–most common in fair-skinned people and the elderly
–one of the most common cancers
–one of the easiest to treat
–has one of the highest survival rates if detected and treated early

105

three types of skin cancer

–basal cell carcinoma, squamous cell carcinoma, and malignant melanoma

106

basal cell carcinoma,

-most common type-least dangerous because it seldom metastasizes-forms from cells in stratum basale

107

squamous cell carcinoma,

arise from keratinocytes from stratum spinosum-lesions usually appear on scalp, ears, lower lip, or back of the hand

108

malignant melanoma

-skin cancer that arises from melanocytes
-often in a preexisting mole
-less than 5% of skin cancers, but most deadly form

109

burns

leading cause of accidental death

110

eschar

burned, dead tissue

111

debridement

removal of eschar

112

first-degree burns

partial thickness burn -involve only the epidermis
•marked by redness, slight edema, and pain
•heal in a few days
•most sunburns are first degree burns

113

second-degree burns

partial thickness burn -involve the epidermis and part of the dermis
•leaves part of the dermis intact

114

third-degree burn

full thickness burn –the epidermis and all of the dermis, and often some deeper tissues (muscles or bones) are destroyed
•often require skin grafts

115

Rules of Nines (Adult)

Estimate Extent of Burn Injury:
–Head: 9%
–Anterior trunk: 18%
–Posterior trunk: 18%
–Arms (9% each): 18%
–Legs (18% each): 36%
–Perineum: 1%

116

skin grafts

third-degree burns require skin grafts

117

autograft

tissue taken from another location on the same person’s body

118

isograft

skin from identical twin

119

homograft (allograft)

from unrelated person

120

heterograft (xenograft)

from another species