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Histology > Skin > Flashcards

Skin Flashcards

1
Q

what is the largest organ in the body?

A

the skin, ~15-20% of body mass

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2
Q

4 main functions of skin

A

protection
sensation
thermoregulation
metabolic function

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3
Q

protection

A

from UV, mechanical, chemical, & thermal insult

Prevents dehydration; provides physical barrier to microorganisms

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4
Q

sensation

A

largest sense organ of body; contains receptors for touch, pressure, pain, & temperature

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5
Q

thermoregulation

A

nsulation via hair & SQ fat; heat loss facilitated by sweat glands & dermal capillary network

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6
Q

metabolic functions

A

energy stored in SQ fat(1’ as triglycerides); Vit D synthesized in skin via hv
Maintains homeostasis; excretory function (sweating); immune defense

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7
Q

3 lays of the skin

A

epidermis
dermis
hypodermis (=subcutis)

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8
Q

what does epidermis consist of

A

keratinized, stratified squamous epithelium

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9
Q

cells of the epidermis are called

A

keratinocytes

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10
Q

thickness of the epidermis

A

from <1 mm to >5 mm; dubbed “thin skin” or “thick skin,” respectively

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11
Q

“Thick skin” has thick, highly — layer

A

keratinized

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12
Q

thick skin is restricted to (2)

A

volar (soles) & palmar (palms) surfaces

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13
Q

thick skin lacks

A

hair (glabrous)

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14
Q

Most of body covered in —, with thin keratinized epidermis

A

“thin skin”

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15
Q

Epidermis lacks blood vessels—do not penetrate

A

basement membrane

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16
Q

Epidermis supplied & nourished by blood vessels in

A

underlying (subjacent) dermis

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17
Q

dermis is composed of

A

dense, irregular, collagenous connective tissue (Type I collagen), interspersed with elastic fibers

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18
Q

Progressive damage to elastic fibers results in

A

“aging”, loss of skin tone

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19
Q

dermis is highly vascular, contains many

A

sensory receptors

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20
Q

what are the two layers of the dermis?

A

papillary layer

deep reticular layer

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21
Q

Papillary layer relatively thin and interdigitates with

A

epidermis

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22
Q

Corrugations increases surface area for —, prevent (2)

A

attachment, prevent shear & mechanical abrasion

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23
Q

Epidermal ridges (rete ridges)

A

epidermal projections into dermis

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24
Q

Dermal ridges(dermal papillae)

A

dermal projections into epidermis

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25
Q

Large dermal ridges in thick skin called

A

fingerprints (= dermatoglyphs); unique to individual

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26
Q

dermal ridges form basis of study of

A

dermatoglyphics

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27
Q

reticular layer compared to papillary layer

A

Deep reticular layerof dermis thicker & less cell than papillary layer

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28
Q

dermis contains (3)

A

hair follicles, sweat & sebaceous glands

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29
Q

dermis interdigitates with underlying

A

hypodermis(= subcutis)

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30
Q

Thick collagen bundles & elastin fibers in reticular layer form lines of tension,

A

Langer’s lines

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31
Q

Skin incisions — to Langer’s lines heal with less scarring

A

parallel

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32
Q

hypodermis is located

A

below dermis

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33
Q

hypodermis

A

layer of loose, irregular connective tissue & adipose tissue (= subcutis= superficial fascia= panniculus adiposus)

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34
Q

vascular plexus consist of (3)

A

Superficial subpapillary plexus, deep cutaneous plexus, & deeper subcutaneous plexus

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35
Q

Subpapillary plexus located at junction of

A

papillary & reticular layers

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36
Q

Cutaneous plexus located at junction of

A

reticular layer & hypodermis

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37
Q

Subcutaneous plexus located deep within

A

hypodermis

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38
Q

largest of the three layers of the vascular plexi

A

subcutaneous plexus

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39
Q

vascular plexi is used in — in (2)

A

Used in thermoregulation—in fingertips & ears

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40
Q

vascular plexus is associated with

A

AV shunts containing glomus bodies

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41
Q

glomus bodies

A

Thickened regions of smooth Mm in wall of arterioles, surrounded by connective tissue capsule

42
Q

vascular plexi bypasses capillary bed, to re-route blood from

A

arterial to venous circulation

43
Q

Skin is continuously (2)

A

grown & replaced

44
Q

skin takes ~25-50 days for cells to travel from deep germinal layer, mature, & be sloughed from

A

superficial epidermis

45
Q

psoriasis

A

absence of a granular layer and abnormal keratohyaline & tonofibrils

46
Q

In psoriasis, keratinocyte maturation only takes ~

A

1 wk

47
Q

Stratum basale=

A

stratum germinativum

48
Q

stratum basale is the — layer

A

basal

49
Q

Mitotic layer of cuboidal germinal cells bound to basement membrane by

A

hemidesmosomes

50
Q

Attach to underlying dermis via (2)

A

anchoring filaments & microfibrils

51
Q

Stratum spinosum

A

“prickle cell layer”

cells look spiny

52
Q

thickest layer of epidermis in thin skin

A

Stratum spinosum

53
Q

Polyhedral cells with

A

prominent intercellular bridges (desmosomes), numerous cytoplasmic processes & lateral folding of cell membrane

54
Q

Predominant cell product, cytokeratin, forms tonofilaments, aggregate into

A

larger tonofibrils, anchor onto desmosomes

55
Q

Stratum granulosum—— cell layer

A

granular

56
Q

Characterized by cells containing basophilic

A

keratohyaline granules

57
Q

keratohyaline granules

A

non-membrane bound, electron dense granules

58
Q

Keratinization of cells represents interaction between

A

keratohyaline granules & tonofibrils

59
Q

Keratinization initiated by release of lysosomal enzymes results in

A

rupture of keratohyaline granules & polymerization of their contents

60
Q

Forms a matrix for tonofibrils of cytokeratin results in

A

amorphous mass of mature keratin

61
Q

Release of lysosomes also results in

A

death of the cell

62
Q

As keratinocytes mature, they

A

die & lose nuclei

63
Q

Cells of granular layer contain membrane-bound, lamellar structures called

A

keratinosomes

64
Q

keratinosomes contain —, provide waterproofing coat for skin cells

A

glycolipids

65
Q

Cells of granular layer mature to form waterproof layer of keratinized cells, with — coating on surface of epidermis

A

glycolipid

66
Q

Stratum lucidum is present only in

A

thick skin

67
Q

Stratum lucidum

A

Homogenous, compact layer of enucleate cells between stratum granulosum & stratum corneum

68
Q

Stratum corneum—(cornified layer)

A

most superficial layer; thickest layer of epidermis in thick skin

69
Q

stratum corner contains

A

flattened, enucleate, dead cell remnants, called squames

70
Q

Composed 1’ of soft keratin—acts as hydrophobic barrier, prevents

A

desiccation

71
Q

desquamation

A

Continuously exfoliated

72
Q

In females, exfoliated cervical epithelial cells routinely examined in — —, to detect cervical cancer

A

Pap smear

73
Q

common skin tumors (3)

A
  • Squamous cell carcinoma
  • Basal cell carcinoma
  • Melanoma
74
Q

squamous cell carcinoma and basal cell carcinoma are derived from

A

epithelial cells

75
Q

melanoma is derived from

A

maloncytes

76
Q

squamous cell carcinoma, basal cell carcinoma, and melanoma are all aggressive cancers with tendency to

A

metastasize

77
Q

First intention healing—from a

A

clean (surgical), approximated incision

78
Q

Incision immediately fills with

A

blood & clots

79
Q

Within 3—24 hrs,

A

neutrophils infiltrate clot (acute phase)

80
Q

Epithelial cells of stratum basale begin mitosis results in

A

epithelial closure (reapproximation) within 24—48 hrs

81
Q

Day 3-7—neutrophils begin to be replaced by

A

macrophages (transition from acute to subacute phase)

82
Q

3 processes: neovascularization, fibroplasia (fibroblasts elaborate collagen), & re-epithelialization (epithelial proliferation) results in

A

production of granulation tissue

83
Q

~ Day 5—incision filled with

A

granulation tissue

84
Q

Week 2—continued fibroplasia & collagen accumulation results in

A

mature granulation tissue

85
Q

progressive decrease in

A

inflammation

86
Q

Presence of inflammatory cells & inflammatory cell products results in

A

itching while healing

87
Q

Month 2—connective tissue scar, without inflammation, covered by

A

intact epithelium

88
Q

With Vit C deficiency, collagen breaks down; old scars can

A

re-open & bleed

89
Q

Keloid

A

excess fibroplasia

90
Q

Keloid results in

A

raised, thickened connective tissue scar

91
Q

Second intention healing—occurs with more extensive loss of tissue, where wound edges do not

A

approximate (e.g., infarct, ulcer, abscess)

92
Q

Following initial clot formation, epithelial cells of — — migrate from edges of wound at ~ 0.5 mm/day

A

stratum basale

93
Q

Takes ~3 weeks to fill a 1 cm wide

A

cut

94
Q

In haired skin, migration of cells from external root sheath of hair follicles augments

A

re-epithelialization

95
Q

Simultaneous proliferation/ maturation of keratinocytes behind migrating front slowly restores multilayered,

A

stratified epidermis

96
Q

Takes ~ 25 days for cells to mature from stratum basale to stratum corneum, results in

A

keratinization

97
Q

Keratinazation of new cells results in

A

desquamation & lifting of scab from periphery after ~ 3 wks

98
Q

wound repair is followed by wound contraction due to

A

myofibroblasts

99
Q

In full thickness abrasion, or third degree burns, re-epithelialization limited by

A

size of wound; grafting generally necessary

100
Q

1st degree—involves

A

only epidermis

101
Q

2nd degree—involves

A

both epidermis & dermis

102
Q

3rd degree— involves

A

all three layers, epidermis, dermis & hypodermis

Histology (32 decks)

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