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BIOSCI 107 Part One > Special Topics: Human Skin > Flashcards

Special Topics: Human Skin Flashcards

1
Q

What is skin engineering?

A

Growing large sheets of skin in the lab to treat burn patients

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2
Q

What is Epidermolysis Bullosa?

A

This is a condition where mutations occur in the proteins that hold layers of skin together. This causes blistering of the skin and mucous membranes. They are trying to use CRISPR gene editing to resolve this condition

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3
Q

What are keloid scars?

A

Scars that grow beyond the wound boundary that are itchy and painful

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4
Q

What is the total body surface area?

A

2m^2

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5
Q

What is the eercentage of total body weight that is skin

A

7-16%

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6
Q

How thick is the skin in the eyelids?

A

0.5mm

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7
Q

How thick is the skin of the palm and sole of feet?

A

4mm or thicker

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8
Q

What are the functions of skin?

A

Protection/barrier, blood reservoir, vitamin D synthesis, thermoregulation, sensation

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9
Q

What is the most important function of the skin?

A

Protection/barrier

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10
Q

What does the skin protect the body from?

A 
Environment 
Chemicals Pathogens 
Heat 
UV
Water loss
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11
Q

How much blood can the skin hold?

A

8-10% of the total blood volume

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12
Q

What is the Vitamin D function of the skin?

A

The skin is the vitamin D precursor. It requires modification by UV before active form can be made in the liver

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13
Q

How do sweat glands contribute to the skins thermoregulation function?

A

The evaporation of sweat cools the body

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14
Q

What does the constriction of blood vessels do?

A

Vessel constriction in the dermis reduces blood flow = reduced heat loss

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15
Q

What does vasodilation of blood vessels do?

A

Vasodilation in the dermis increases blood flow = increased heat loss

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16
Q

What sensations can the skin detect?

A

Touch/pressure, pain, temperature

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17
Q

What is the top layer of the skin?

A

The epidermis

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18
Q

What is the function of the epidermis?

A

To provide a barrier and continued renewal

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19
Q

What does the skin mainly consist of?

A

Layers of keratinocytes

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20
Q

Why does the skin have no structural strength?

A

it is mainly made of dead or dying keratinocytes, so there is no connective tissue in the epidermis to provide strength

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21
Q

What are keratinocytes?

A

are the cells that make up the epidermis and produce keratin filaments which is important for the barrier function of the epidermis (they look like cobblestones under a microscope)

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22
Q

What and where is thin skin?

A

the majority of skin is thin skin and it is when the epidermis has 4 layers of keratinocytes

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23
Q

What and where is thick skin?

A

it is in the fingertips, palms, soles and has 5 layers. The fifth layer is Stratum Lucidum

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24
Q

Does the skin have vasculature?

A

No it doesn’t, all nutrient supply and waste removal through the dermis

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25
Q

What does stratification refer to?

A

the different layers in the epidermis

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26
Q

What is the function of stratification?

A

Crucial for barrier function and continued renewal of the epidermis

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27
Q

What do cells at the bottom of the epidermis do?

A

Keratinocytes proliferate at the bottom of the epidermis (Stratum Basale) which pushes cells up and away from the dermis

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28
Q

What happens to cells as they move away from the dermis?

A

They undergo programmed cell death

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29
Q

How long does complete epidermal turnover take?

A

A month

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30
Q

What is the acronym for the layers of the epidermis?

A

Come Lets Get Sun-Burnt

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31
Q

What is the bottom layer of the epidermis?

A

Stratum Basale

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32
Q

What are keratinocyte stem cells and what do they do?

A

They are the reservoirs of cells (keratinocytes, stem cells) for a lifetime of renewal.
Keratinocyte stem cells can divide so that one cell remains a stem cell and the others become transit amplifying keratinocytes

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33
Q

What occurs in the Stratum Basale?

A

Transit amplifying keratinocytes proliferate (divide rapidly but for a short period before they die) a lot to provide cells for all the top layers

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34
Q

What is the layer above the Stratum Basale?

A

Stratum Spinosum

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35
Q

How thick is the Stratum Spinosum?

A

8-10 layers of cells/keratinocytes

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36
Q

What happens to keratinocytes in the Stratum Spinosum

A

Keratinocytes begin to flatten out

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37
Q

What holds keratinocytes together in the Stratum Spinosum and what is this important for?

A

Keratin intermediate filaments and desmosomes. This is important for the barrier function of the skin

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38
Q

What layer is above the Stratum Spinosum?

A

Stratum Granulosum

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39
Q

What happens in the Stratum Granulosum

A

Flattened keratinocytes undergo apoptosis (programmed cell death)

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40
Q

What are lamellar granules?

A

Organelles in keratinocytes that fuse to the plasma membrane and begin to release lipid rich secretions to help form the barrier in the Stratum Granulosum

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41
Q

What is keratohyalin?

A

Protein structure in granules of keratinocytes. These dark granules help form keratin intermediate filaments into keratin (holds keratinocytes together)

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42
Q

What layer is above the Stratum Granulosum

A

Stratum Lucidum

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43
Q

Where is the Stratum Lucidum found?

A

ONLY in thick skin (fingertips, palms, soles)

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44
Q

What is the top layer of the epidermis?

A

Stratum Corneum

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45
Q

How thick is the Stratum Corneum

A

25-30 layers of flattened dead keratinocytes

46
Q

What is the function of the Stratum Corneum

A

To form a barrier to keep moisture in and the outside world out

47
Q

What are keratinocytes like in the Stratum Corneum

A

They have finished undergoing apoptosis and are overlapping like the scales of a snake

48
Q

What is the interface between the dermis and epidermis

A

The Basement Membrane

49
Q

What are the proteins in the Basement Membrane

A

Collagen IV, Perlecan, Nidogen, Laminin 332

50
Q

What do keratinocytes in the basal layer attach to?

A

the proteins in the basement membrane

51
Q

What is the Basement membrane important for?

A

It is important for the epidermal attachment to the dermis

52
Q

What can a mutation in the basement membrane proteins cause?

A

Epidermolysis Bullosa (keratinocytes cannot attach to BM)

53
Q

What are rete ridges/dermal papillae?

A

wavelike ridges in the boundary between the epidermis and dermis

54
Q

What is the function of rete ridges?

A

their contour provides resistance to shear forces

55
Q

Where do melanocytes reside?

A

in the epidermal side of the basement membrane

56
Q

What do melanocytes make?

A

Melanosomes

57
Q

What is contained in melanosomes?

A

Melanin

58
Q

How are melanosomes transferred to keratinocytes?

A

Melanosomes are transferred to keratinocytes by dendrites on melanocytes (36 keratinocytes at a time)

59
Q

What is melanin?

A

a pigment that gives skin its colour

60
Q

What is Pheomelanin

A

Pigment in Melanin that gives skin red and yellow colours

61
Q

What is Eumelanin

A

Pigment in Melanin that gives skin its brown and black colour

62
Q

What is the function of melanin in keratinocytes?

A

They form a nuclear cap to protect the nucleus of keratinocytes and its DNA from UV

63
Q

What is a Langerhan cell?

A

Intraepidermal macrophage (immune cell in the epidermis)

64
Q

What is the function of Langerhan cells?

A

to surveil the epidermis for foreign organisms

65
Q

What is beneath the basement membrane?

A

The dermis

66
Q

What is the dermis made of?

A

A dense matrix of collagen and elastin fibres (connective tissue)

67
Q

What are some properties of the dermis

A

It is strong and supple and, unlike the epidermis, it is very stable with little turnover

68
Q

Where is the dermis the thickest

A

in the soles and palms but thickness varies all over the skin

69
Q

What are fibroblasts?

A

CT cells that secrete/produce collagen and elastin

70
Q

Main property of collagen

A

Strength

71
Q

Main property of elastin

A

Elasticity

72
Q

Names of the layers of the dermis

A

The Papillary and Reticular Dermis

73
Q

What is the top layer of the dermis

A

The Papillary dermis

74
Q

What is the papillary dermis made of

A

loose areolar connective tissue

75
Q

What is the cell density of the papillary dermis

A

It has a high cell density (can be seen by lots of nuclei)

76
Q

What is the bottom layer of the dermis?

A

The Reticular Layer

77
Q

What is the reticular dermis made of?

A

Dense irregular connective tissue

78
Q

What is the cell density of the reticular dermis?

A

Low cell density (few nuclei)

79
Q

Is the dermis vascular?

A

Yes, it contains blood vessels that supply nutrients and remove waste for both dermis and epidermis

80
Q

What is the function of lamnin in the dermis?

A

Lamnin lines vessels of vasculature system of dermis

81
Q

What is the function of Alpha SMA in the dermis?

A

Alpha SMA is a contractile protei

82
Q

What are the three types of wounds?

A

Superficial, partial thickness and full thickness

83
Q

What are superficial wounds?

A

wounds that only damage the epidermis

84
Q

Where do keratinocytes migrate from in wound healing?

A

Wound edges and dermal appendages (sweat glands, hair follicles, sebaceous glands)

85
Q

How does wound healing occur in superficial wounds?

A

Healing occurs by migration of keratinocyte from the wound edges and dermal appendages (sweat glands, hair follicles, sebaceous glands)
Once all keratinocytes are in contact on all sides, then stratification can occur to reform the epidermis

86
Q

What are partial thickness wounds?

A

Wounds where all of the epidermis and some of the dermis has been destroyed

87
Q

What is the first phase of partial thickness wound healing?

A

Inflammatory phase

88
Q

What happens in the Inflammatory phase of partial thickness wound healing?

A

immune cells come in and clean up the wound

89
Q

What is the second phase of partial thickness wound healing?

A

Migratory phase

90
Q

What happens in the Migratory phase of partial thickness wound healing?

A

keratinocytes migrate from the wound edge and appendages, fibroblasts migrate in to the clot make collagen fibres

91
Q

What is the third phase of partial thickness wound healing?

A

Proliferative phase

92
Q

What happens in the Proliferative phase of partial thickness wound healing?

A

keratinocytes proliferate

93
Q

What is the fourth phase of partial thickness wound healing?

A

Maturation phase

94
Q

What happens in the Maturation phase of partial thickness wound healing?

A

epidermal stratification then scab falls off

95
Q

What is a full thickness wound?

A

All of the epidermis and dermis is destroyed

Hypodermis can be destroyed too, exposing bone and muscle

96
Q

Why is wound healing hard in full thickness wounds?

A

Wound repair is very difficult because all of the reservoirs of epidermal stem cells have been destroyed (wound edges are gone).

97
Q

What do full thickness wounds heal as?

A

Scar tissue

98
Q

Which type of wound is intervention needed?

A

Full thickness wounds to improve patient outcomes

99
Q

What is the “gold standard” in healing full thickness wounds

A

Split thickness grafts which cover the wound

100
Q

Where does a split thickness graft come from

A

It takes all the epidermis and part of the dermis from undamaged skin (donor site)

101
Q

How fast do donor sites heal?

A

10-14 days

102
Q

What happened in the first 1-2 weeks post Whakaari/White Island Eruption

A

Patients were stabilised

103
Q

What did the first surgery for Whakaari/White Island Eruption
patients do

A

First surgery was to remove all burnt skin, critical for skin graft success . Any residual necrotic tissue will negatively affect graft take

104
Q

What did the second surgery for Whakaari/White Island Eruption
patients do

A

patients received split thickness skin grafts

105
Q

When is there too much damage to do a split thickness skin graft

A

Great than 30% of the total body surface area

106
Q

What are uncovered wound areas covered with

A

cadaveric skin

107
Q

What is the function of cadaveric skin

A

Cadaveric skin acts as a temporary wound dressing, eventually gets rejected

108
Q

What is an alternative to split thickness skin grafts for burn wound patients

A

Engineered skin

109
Q

What is the process of skin engineering

A

Start with a small sample of undamaged patient skin
Isolate and expand skin cells in the laboratory
Grow enough skin to cover all wounds
Digest sample of patient skin (so it doesn’t get rejected)
Isolate and grow fibroblasts and keratinocytes
Grow large sheets of autologous, full thickness skin
Permanent wound coverage solution

110
Q

What are the limitations of skin engineering?

A

No pigmentation
No hair follicles
No sweat glands
No sebaceous glands

111
Q

What has denovoSkin done?

A

completed a Phase I clinical trial in 10 patients

of skin engineering (100 fold return on patient skin in 4-6 weeks)

BIOSCI 107 Part One (12 decks)

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