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Histology > Skin > Flashcards

Skin Flashcards

1
Q

what are the functions of the skin

A

-protection
- sensation
- thermoregulation
- metabolic functions

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2
Q

how does the skin function in protection

A

from UV, mechanical, chemical, and thermal insult. prevents dehydration; provides physical barrier to microorganisms

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3
Q

how does the skin function in sensation

A

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

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4
Q

how does the skin function in thermoregulation

A

insulation via hair and subcutaneous fat; heat loss facilitated by sweat glands and dermal capillary network

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5
Q

how does the skin function in metabolic functions

A

energy stores in subcutaneous fat
- vitamin D synthesized in the skin via sunlight
-maintains homeostasis; sweating and immune defense

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6
Q

what are the 3 main layers of the skin

A

-epidermis
- dermis
- hypodermis (subcutis)

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7
Q

what does the epidermis consist of

A

keratinized stratified squamous epithelium

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8
Q

what are the cells of the epidermis called

A

keratinocytes

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9
Q

what are the two types of epidermis

A

thick skin and thin skin

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10
Q

what is the character of thick skin

A

highly keratinized, no hair

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11
Q

where is thick skin located

A

soles of feet and palms of hands

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12
Q

what does glabrous mean

A

lacking hair

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13
Q

does the epidermis have blood vessels

A

no

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14
Q

what is the epidermis supplied by

A

blood vessels in underlying dermis

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15
Q

what is the dermis composed of

A

dense, irregular collagenous connective tissue (type 1 collagen, with elastic fibers

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16
Q

how does aging of skin occur

A

progressive damage to elastic fibers from sunlight

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17
Q

describe what supplies the dermis

A

highly vascular and contains many sensory receptors

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18
Q

what are the 2 layers of the dermis

A

superficial papillary layer and the deep reticular layer

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19
Q

describe the papillary layer

A

relatively thin- interdigitates with epidermis

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20
Q

what do corrugations do

A

increase surface area for attachment, prevent shear and mechanical abrasion

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21
Q

what are epidermal ridges

A

epidermal projections into the dermis

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22
Q

what is another term for epidermal ridges

A

rete ridges

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23
Q

what are dermal ridges

A

dermal projections into epidermis

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24
Q

what is another term for dermal ridges

A

dermal papillae

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25
Q

what are fingerprints

A

large dermal ridges in thick skin

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26
Q

what is another word for fingerprints

A

dermatoglyphs

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27
Q

describe the deep reticular layer of the dermis

A

thicker and less cell than papillary layer
- contains hair follicles, sweat and sebaceous glands
- interdigitates with hypodermic (subcutis)

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28
Q

what are langer’s lines

A

thick collagen bundles and elastin fibers in reticular layer form these lines in the deep reticular layer

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29
Q

how do skin incisions heal with less scarring

A

parallel to langer’s lines

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30
Q

describe the hypodermis

A

layer of loose, irregular connective tissue and adipose tissue below the dermis

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31
Q

what are some other terms for hypodermis

A

subcutis, superficial fascia, panniculus adiposus

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32
Q

what are the vascular plexi

A

superficial subpapillary plexus, deep cutaneous plexus and deeper subcutaneous plexus

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33
Q

where is the subpapillary plexus located

A

at the junction of papillary and reticular layers

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34
Q

where is the cutaneous plexus located

A

the junction of reticular layer and hypodermis

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35
Q

where is the subcutaneous plexus located

A

deep within hypodermis, largest of the three

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36
Q

what is the purpose of the vascular plexi

A

thermoregulation in fingertips and ears, associated with AV shunts containing glomus bodies

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37
Q

what are glomus bodies and what is their function

A

-thickened regions of smooth muscle in the wall or arterioles surrounded by connective tissue capsule
-bypass capillary bed and reroute blood from arterial to venous circulation

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38
Q

how is skin grown and replaced

A

cells travel from deep germinal layer, mature and be sloughed from superficial epidermis

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39
Q

what happens in psoriasis

A

keratinocyte maturation only takes 1 week, absence of a granular layer and abnormal keratohyaline and tonofibrils

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40
Q

what are the layers of the epidermis from deep to superficial

A

stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

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41
Q

describe the stratum basale

A

mitotic layer of cuboidal germinal cells bound to BM by hemidesmosomes

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42
Q

how is the stratum basale attached to the underlying dermis

A

anchoring filaments and microfibrils

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43
Q

describe the stratum spinosum

A

prickle cell layer, cells look spiny; thickest layer of epidermis in thin skin

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44
Q

describes the cells of the stratum spinosum

A

polyhedral cells with prominent intercellular birdges, numerous cytoplasmic processes and lateral folding of cell membrane

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45
Q

what do polyhedral cells produce

A

cytokeratin

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46
Q

what does cytokeratin do

A

forms tonofilaments that aggregate into tonofibrils and anchor to desmosomes

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47
Q

describe the stratum granulosum

A

granular cell layer
- characterized by cells containing basophilic keratohyaline granules

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48
Q

what are keratohylaine granules

A

non-membrane bound electron dense granules

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49
Q

what is the keratinization of cells

A

represents interaction between keratohyaline granules and tonofibrils

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50
Q

what is keratinization initiated by

A

release of lysosomal enzymes ruptures keratohyaline granules and polymerization of their contents forms a matrix for tonofibrils of cytokeratin which results in mature keratin

51
Q

what happens as keratinocytes mature

A

die and lose nuclei

52
Q

what do cells of the granular layer contain

A

membrane-bound, lamellar structures called keratinosomes

53
Q

what do keratinosomes contain

A

glycolipids, provide waterproofing coat for skin cells

54
Q

where is the stratum lucidum present

A

in thick skin

55
Q

describe the stratum lucidum

A

homogenous, compact layer of enucleate cells between stratum granulosum and stratum corneum

56
Q

what is the stratum corneum

A

most superficial layer; thickest layer of epidermis in thick skin

57
Q

describe the cells of the stratum corneum

A

flattened, enucleate, dead cell remnants called squames

58
Q

what are squames and what is their function

A

primarily soft keratin that acts as hydrophobic barrier to prevent dessication

59
Q

what is desquamination

A

exfoliation

60
Q

what are the types of common skin tumors

A

squamous cell carcinoma, basal cell carcinoma, melanoma

61
Q

what skin tumors are derived from epithelial cells

A

squamous cell carcinoma and basal cell carcinoma

62
Q

what skin tumors are derived from melanocytes

A

melanoma

63
Q

what happens in first intention healing

A

from a clean incision
-incision immediately fills with blood and clots
- within 3-24 hours neutrophils infilatrate clot (acute phase)
-epithelial cells of stratum basale begin mitosis -> epithelial closure within 24-48 hours (reapproximation)
- day 3-7 neutrophils begin to be replaced by macrophagees (transition from acute to subacute phase)
- day 5 incision filled with granulation tissue
- week 2- continued fibroplasia and collagen accumulation ->mature granulation tissue. progressive decrease in inflammation. itching from inflammatory cell products
- month 2- CT scar

64
Q

what are the 3 processes in the transition from acute to subacute phase (days 3-7)

A

neovascularization, fibroplasia (fibroblasts elaborate collagen), re-epithelialization (epithelial proliferation) -> production of granulation tissue

65
Q

what happens with vitamin C deficiency

A

collagen breaks down, old scars can re-open and bleed

66
Q

what happens in second intention healing

A
  • clot formation, epithelial cells of stratum basale migrate from edges of wound
  • takes 3 weeks to fill a 1 cm wide cut
  • in haired skin, migration of cells from external root sheath of hair follicles augments re-epithelialization
  • simultaneous proliferation of keratinocytes slowly restores multilayered stratified epidermis
  • takes 25 days for cells to mature from stratum basale to stratum corneum -> keratinization
  • keratinization of new cells and lifting of scab after 3 weeks
  • followed by wound contraction due to myofibroblasts
    -in full thickness abrasion or third degree burns, re-epithelialization limited by size of wound
67
Q

when does second intention healing occur

A

with more extensive loss of tissue where wound edges do not approximate

68
Q

what is a keloid

A

raised thickened connective tissue scare

69
Q

what is a keloid caused from

A

excess fibroplasia

70
Q

what does a 1st degree involve

A

only epidermis

71
Q

what does a second degree burn involve

A

epidermis and dermis

72
Q

what does a third degree burn involve

A

all three layers, epidermis, dermis, hypodermis

73
Q

what are melanocytes derived fromm

A

neuroectodermal dendritic cells in epidermis

74
Q

where are melanocytes found

A

usually restriced to basal layer

75
Q

where might the cytoplasmic extensions of melanocytes extend into

A

stratum spinosum

76
Q

what do melanocytes do

A

produce melanin

77
Q

what is melanin released from and taken up by

A

released from melanosomes in melanocytes.
-taken up by epidermal cells

78
Q

how do you idenitify melanocytes

A

dark staining nuclei, clear cytoplasm

79
Q

what are the 2 types of melanin

A

eumelanin and pheomelanin

80
Q

where is eumelanin found and what do their melanocytes look like

A

darked haired individuals, elongated melanocytes

81
Q

where is pheomelanin found and what do their melanocytes look like

A

individuals with red or blonde hair, oval melanocytes

82
Q

describe how melanocytes operate and are distrubuted across peoepl

A

equal number of melanocytes across people but variable rates of melanin production and degradation by lysosomal enzymes

83
Q

how do light skin people produce and process pigment compared to dark skinned

A

light skineed produce less pigment or digest pigment faster

84
Q

what is vitiligo

A

autoimmune disease, destruction of melanocytes -> depigmentation

85
Q

what controls melanin synthesis

A

melanocyte stimulating hormone (MSH) in pituitary

86
Q

how is melanin synthesized (mechanism)

A

-tyrosine precursor oxidized to DOPA by tyrosinase located in premalosomes
- DOPA -> melanin in melanosomes

87
Q

what happens with albinos

A

lack tyrosinase so DOPA and melanin not formed
-premelanosomes form but dont mature

88
Q

what can tyrosinase be used for

A

as a marker to differentiate melanocytes from keratinocytes containing phagocytosed melanin
- Tumor ID

89
Q

what does melanin do

A

shield nucleus from UV rays , inhibits mutagenesis

90
Q

what does UV stimulate

A

melanin synthesis

91
Q

what is melanin necessary for

A

normal neural development

92
Q

what are langerhans cells

A

fixed tissue macrophages- phagocytic antigen presenting cells

93
Q

what do langerhans cells contain

A

birbeck granules

94
Q

where are langerhans cells located

A

stratum spinosum

95
Q

what are langerhans cells involved in

A

contact allergic dermatitis

96
Q

what are skin appendages and examples

A

embyrological outgrowths of epidermis
ex: hair, nails, sebaceous sweat glands

97
Q

what is terminal hair

A

coarse hair on scalp, axillae and pubis

98
Q

what does the hair shaft consist of

A

outer cortex and inner medulla

99
Q

what is the hair shaft covered by and what is its function

A

cuticle of overlapping keratin plates to prevent the matting of hair

100
Q

what is the hair shaft produced by

A

hair follicles that are downgrowths of epithelium surrounded by collagen sheaths

101
Q

where does hair growth occur

A

in the deep terminal expansion of follicle called the hair bulb

102
Q

what is the hair bulb lined with

A

actively dividing epithelial cells homologous of stratum basale

103
Q

what is the dermal papilla and where is it located

A

it is a finger-like invagination of dermis containing blood vessles and is located at the base of the bulb

104
Q

what happens as epithelial cells lining hair bulb mature

A

fill with hard keratin filaments arranged in parallel bundles

105
Q

how does hair get color

A

melanocytes adjacent to hair follicle produce melanin and becomes incorporated into cortex

106
Q

what do the internal and external root sheath do

A

surround and protect developing hair and line hair follicle

107
Q

what is the glassy membrane

A

a modified BM separates hair bulb from surrounding epidermis

108
Q

what is the function of hair

A

thermoregulation and protection

109
Q

what is the internal root sheath made up of

A

CT

110
Q

what is the external root sheath made of

A

cellular

111
Q

where is hair absent

A

on thick skin of palms and soles

112
Q

what are arrector pili muscles

A

bundles of smooth muscle cells that attach to hair follicle sheath and insert on epidermal ridges

113
Q

what happens when arrector pili muscles contracct

A

raises hair -> goosebumps

114
Q

what is arrector pili muscle contraction caused by

A

sympathetic stimulation due to cold, fear, aggression

115
Q

how are arrector pili muscles spatially oriented to the hair shaft

A

30 degree angle

116
Q

what are the phases of hair growth and what happens in each

A

-anagen- growth phase
- catagen- involuting phase (loss of blood supply)
- telogen- resting phase
-exogen- shedding of old hair shaft

117
Q

what is vellus hair

A

fine body hair in children

118
Q

what is androgenic alopecia

A

most common form of hair loss, genetic and androgen dependent
- high levels of 5alpha reductase, the enzyme that converts testosterone to dihydrozytestosterone results in follicular atrophy

119
Q

where is the nail plate

A

rests of stratified squamous epithelium of nail bed

120
Q

where is the nail root located

A

extends into dermis and attaches to periosteum of distal phalanx

121
Q

where does nail growth occur

A

by proliferation and differentiation of epithelium at nail root in germinative zone of nail matric

122
Q

what is the lunula and what covers it

A

the white crescent base of nail, covered by superficial cuticle

123
Q

what happens as epthithelial cells mature on the nail

A

fill with keratin and die forming nail plate

124
Q

what is the nail plate made of

A

densely packed, hard keratin filaments embedded in amorphous matrix

Histology (27 decks)

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