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FD9 > 14 - Skin Barrier > Flashcards

14 - Skin Barrier Flashcards

1
Q

The tough outer protective layer of an animal or plant that demarcates the body from the external environment

A

Integument

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2
Q

Cell-cell adhesive junction that seals the intercellular space and controls paracellular molecular movement

A

Occlusive junction

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3
Q

The occlusive junction of invertebrates is called a _____, and that of vertebrates is called a _____

A

Septate junction

Tight junction

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4
Q

Fourteen-sided polyhedron composed of eight hexagons and six squares
Proposed as the best shape for packing equal-sized cells together to fill the space using the minimal surface area of each cell

A

Kelvin’s tetrakaidecahedron

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5
Q

The loss of water that passes from inside to outside a body through the epidermis
Basically in proportion to the level of barrier damage or formation

A

Transepidermal water loss

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6
Q

Compartmentalizes the cell from the external environment in unicellular organisms

A

Lipid bilayer membrane

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7
Q

Because the lipid bilayer membrane is highly fragile, most unicellular organisms have an additional barrier structure outside of the cell membrane (ie, _____) that functions as a type of armor

A

Cell wall

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8
Q

The cell membrane of unicellular organisms corresponds to the _____ in multicellular organisms

A

Epidermis

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9
Q

The stratum granulosum consists of at least _____ layers of flattened granular cells

A

Three

SG1, SG2, SG3

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10
Q

Tight junctions seal the intercellular spaces in the _____ layer

A

SG2

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11
Q

The stratum corneum consists of dead cornified cells (corneocytes) and functions as an _____ interface barrier

A

Air-liquid

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12
Q

Under the stratum corneum, cells area immersed in a water environment. The extracellular water environment of the epidermis is divided into two parts by the tight junction barrier, which is a _____ interface barrier

A

Liquid-liquid

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13
Q

Epidermal cells proliferate only in the _____, differentiate with detachment from the basement membrane, move upward, become flattened at the _____, form a tight junction at the _____, lose the tight junction at _____, terminally differentiate into corneocytes, and detach from the top of the cornified layer as squamous scales

A

Basal layer
Stratum granulosum
SG2 layer
SG1 layer

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14
Q

The stratum corneum in humans is approximately _____ micrometers thick and contains about _____ layers of cornified cells

A

10-20

10-25

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15
Q

Diseases affecting cornified envelope formation (gene and protein affected)

A
  1. Vohwinkel syndrome with ichthyosis (LOR - loricrin)

2. ARCI 1 (TGM1 - transglutaminase 1)

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16
Q

Diseases affecting cholesterol biosynthesis (gene and protein affected)

A
  1. CHILD syndrome (NSDHL - NAD(P)H steroid dehydrogenase-like protein)
  2. MCCPD (MSMO1 - methylsterol monooxygenase 1)
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17
Q

Diseases affecting acylceramide biosynthesis (gene and protein affected)

A
  1. ISQMR (ELOVL4 - elongation of very-long-chain fatty acid-like 4)
  2. ARCI5 (CYP4F22 - cytochrome P450 4F22)
  3. ARCI9 (CERS3 - ceramide synthetase 3)
  4. Chanarin-Dorfman syndrome (ABHD5 - ABHD5/CGI58)
  5. ARCI10 (PNPLA1 - patatin-like phospholipase domain containing 1)
  6. ARCI2 (ALOX12B - arachidonate 12-lipoxygenase type 12R)
  7. ARIC3 (ALOXE3 - arachidonate lipoxygenase 3)
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18
Q

Diseases affecting lipid transport (gene and protein affected)

A
  1. ARCI4A (ABCA12 - ATP-binding cassette A12)

2. ARCI4B/Harlequin ichthyosis (ABCA12 - ATP-binding cassette A12)

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19
Q

Diseases affecting desquamation (gene and protein affected)

A
  1. ARCI11 (ST14 - maltriptase)

2. Netherton syndrome (SPINK5 - LEKTI)

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20
Q

Diseases affecting desmosomes and corneodesmosomes (gene and protein affected)

A
  1. Peeling skin syndrome 1 (CDSN - corneodesmosin)

2. SAM syndrome (DSG1 - desmoglein 1)

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21
Q

Diseases filaggrin metabolism (gene and protein affected)

A
  1. Ichthyosis vulgaris (FLG - filagrrin)

2. ARCI12 (CASP14 - caspase 14)

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22
Q

Diseases affecting tight junctions (gene and protein affected)

A
  1. Neonatal ichthyosis sclerosing cholangitis syndrome (CLDN1 - claudin-1)
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23
Q

Basic diffusion barrier on the body surface of both monocellular organisms and multicellular organisms

A

Lipid bilayer cell membrane

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24
Q

Y/N: Both monocellular organisms and multicellular organisms are equipped with additional outer barriers

A

Yes

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25
Q

Corneocytes are terminally differentiated dead keratinocytes that adhere to one another via proteinaceous cell-cell adhesion complexes called _____ and the adhesive force of intercellular lipid lamellae

A

Corneodesmosomes

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26
Q

Y/N: The basket-weave structure of the stratum corneum is an artifact of the processing of specimens

A

Yes

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27
Q

Basic structure of the stratum corneum: protein-based bricks (_____) and lipid-based mortar (_____)

A

Corneocytes

Intercellular lipid lamellae

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28
Q

The surface of the corneocytes is coated with a thin layer of ceramide (_____)

A

Lipid envelope

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29
Q

During cornification, a _____ consisting of a 10-nm-thick layer of highly cross-linked insoluble proteins is formed beneath the plasma membrane, and the lipid bilayer of plasma membrane is replaced by a 5-nm-thick layer of acylceramides, which is called _____

A

Cornified cell envelope

Corneocyte lipid envelope

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30
Q

_____ expressed in granular layer cells associated with the inner surface of the plasma membrane in a calcium-dependent manner and are cross-linked to one another by _____

A

Envoplakin, periplakin, and involucrin

Transglutaminase 1

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31
Q

Before the scaffold covers the inner surface of the plasma membrane, _____ are produced from the Golgi complex and become fused to the plasma membrane

A

Lamellar bodies

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32
Q

The limiting membrane of lamellar bodies is rich in _____ composed of omega-hydroxylated ultra-long-chan fatty acids

A

Acylceramides

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33
Q

The fusion of the _____ with the plasma membrane gradually increases the amount of acylceramides within the lipid bilayer of the plasma membrane

A

Limiting membrane

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34
Q

The acylceramides eventually replace the plasma membrane, which is called the _____

A

Corneocyte lipid envelope

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35
Q

On the inner surface of the scaffold, loricrin molecules are translocated from the cytosol and covalently cross-linked onto the scaffold to build the

A

Cornified cell envelope

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36
Q

Insoluble protein that may contribute to the water resistance of the cornified cell envelope
Eventually becomes the major component of the cornified cell envelope

A

Loricrin

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37
Q

Keratinocytes of the stratum granulosum develop a specific system of _____ that allow secretion of intercorneocyte lipid lamellae

A

Lamellar bodies

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38
Q

Produced from the Golgi complex and stored within the cytoplasm in SG3 cells as intracellular vesicles

A

Lamellar bodies

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39
Q

ABCA12 functions in cellular lipid trafficking on the limiting membrane of lamellar bodies, in which severe defects cause

A

Harlequin ichthyosis

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40
Q

After extrusion of the lamellar bodies into the extracellular spaces, the (polar/nonpolar) lipids are enzymatically converted into (polar/nonpolar) products

A

Polar

Nonpolar

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41
Q

_____ are hydrolyzed to generate ceramides, and ____ are converted into free fatty acids

A

Glycosphingolipids

Phospholipids

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42
Q

Very dense structure packed into the interstices of corneocytes, thus forming a water-impermeable barrier

A

Stratified lipid bilayer

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43
Q

Major classes of lipids in the stratum corneum

A

Cholesterol
Free fatty acids
Ceramides

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44
Q

Y/N: Basal-layer keratinocytes are not capable of resorbing cholesterol from the circulation

A

No - capable

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45
Q

Y/N: Epidermal keratinocytes actively biosynthesize cholesterol and free fatty acids

A

Yes

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46
Q

The majority of the cholesterol in the epidermis is synthesized in situ from

A

Acetyl coenzyme A

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47
Q

The rate-limiting step in cholesterol biosynthesis is catalyzed by

A

Hydroxymethylglutaryl CoA reductase

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48
Q

The cholesterol biosynthesis pathway in the epidermis is also important for the production of vitamin

A

D

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49
Q

The metabolic intermediate of cholesterol biosynthesis, _____, is converted to previtamin D in a photolytic reaction by UVB radiation; this is followed by thermal isomerization to form vitamin D3

A

7-dehydrocholesterol

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50
Q

Free fatty acid synthesis originates from _____, produced from acetyl-CoA via acetyl-CoA carboxylase

A

Malonyl-CoA

51
Q

Fatty acids unable to be produced by the human body

A

Essential fatty acids

52
Q

Consist of long-chain amino alcohols, called sphingoid bases, linked to a fatty acid via an amide bond

53
Q

Whereas ceramides are a minor lipid component in the mammalian body (

54
Q

Major cell-cell adhesion structure in the granular, spinous, and basal layers

A

Desmosomes

55
Q

Secreted by lamellar bodies int the extracellular spaces surrounding the SG1 cells

A

Corneodesmosin

56
Q

Corneodesmosis is integrated into the desmosomes, resulting i the formation of

A

Corneodesmosomes

57
Q

Specific cell adhesion structures between corneocytes

A

Corneodesmosomes

58
Q

The outermost corneocytes are detached, one by one, from the top layer of the stratum corneum; this process is called

A

Desquamation

59
Q

The major proteases involved in the degradation of corneodesmosomes are

A

Serine proteases belonging to the kallikrein group

60
Q

Kallikreins _____ are known to exist in the stratum corneum

A

5, 7, and 14

61
Q

The protease activity of the activated kallikreins is thought to be inhibited by the direct binding of

A

Lymphoepithelial Kazal-type-related inhibitor

62
Q

The inhibition of kallikreins by LEKTI (promote/prevent) premature desquamation

63
Q

The (lower/higher) pH of the intercellular spaces in the outer layers of the stratum corneum is thought to facilitate the dissociation of kallikreins from LEKTI and the kaiilkrein-dependent degradation of corneodesmosomes

64
Q

Congenital defects of _____ induce congenital ichthyosis, probably caused by insufficiency activation of kallikrein proteases

A

Maltriptase

65
Q

Congenital defects of _____ induce Netherton syndrome, probably caused by the enhanced degradation of corneodesmosomes by kallikreins

66
Q

Major protein of the stratum corneum

67
Q

In humans, filaggrin is expressed only in

A

Cornified stratified epithelia

68
Q

Expressed in the stratum granulosum and forms intracellular aggregates known as keratohyalin granules

A

Profilaggrin

69
Q

Water-soluble small molecules permeate into the _____ layers of the statum corneum where protein structure is proteolytically degraded

70
Q

In the _____ layers of the stratum corneum, filaggrin degraded into natural moisturizing factors

71
Q

In the _____ layers of the stratum corneum, filaggrin monomers bundle keratin filaments

72
Q

Y/N: Most patients with severe barrier defects, such as those with Netherton syndrome, have multiple allergies

73
Q

Y/N: Most patients who have mutations in the filaggrin gene basically develop ichthyosis vulgaris, and only some of these patients develop allergic disease

74
Q

Major pathway by which external molecules can penetrate the stratum corneum

A

Paracellular route

75
Q

After passing through the stratum corneum, small molecules such as haptens can easily permeate the dermis, probably through the

A

Transcellular pathway

76
Q

In simple epithelia, the tight junctions are located at the

A

Apical-most part of the apical junctional complex

77
Q

The cell membrane is divided into two parts at the _____ - the apical cell membrane and basolateral cell membrane

A

Tight junctions

78
Q

Tight junctions consist of tight junction strands, which are mainly composed of

A

Four-transmembrane proteins of claudins

79
Q

The flattened variation of Kelvin’s tetrakaidecahedron is seen in the

A

Stratum corneum

Stratum granulosum

80
Q

The physical properties of the skin surface itself prevents bacterial growth, that is, a (low/high) carbohydrate and water content and a weakly (basic/acidic) pH

A

Low

Acidic

81
Q

pH of skin

82
Q

The weak acidic pH of the skin is due to various substances, such as _____ from sebaceous glands or derived from phospholipid hydrolysis in the stratum corneum, _____ secreted from eccrine glands, _____ mostly derived from the degradation products of filaggrin, and metabolites produced by microorganisms

A

Free fatty acids
Lactic acid
Urocanic acid

83
Q

Evolutionary ancient innate immune effectors produced by almost all plants and animals
Also act as “alarmins” to alert host cells to react to injuries and microbial invasions

A

Antimicrobial proteins

84
Q

Two major antimicrobial proteins of the skin

A

Cathelicidins

Beta-defensins

85
Q

Keratinocytes in the (hair follicle/interfollicular epidermis) constitutively produce cathelicidins and beta-defensis at a higher level than the keratinocytes of the (hair follicle/interfollicular epidermis)

A

Hair follicle

Interfollicular epidermis

86
Q

The microenvironment of the (hair follicle/interfollicular epidermis) facilitates bacterial colonization much more readily than that of the (hair follicle/interfollicular epidermis)

A

Hair follicle

Interfollicular epidermis

87
Q

Dominant commensal bacterium of the skin microbiota

A

Staphylococcus epidermidis

88
Q

Defensins and cathelicidins are usually (anionic/cationic) and interact with the bacterial membrane surface through electrostatic interactions

89
Q

Some _____ form pores in the bacterial membrane to disrupt membrane integrity and promote bacterial lysis

90
Q

Bind to bacterial membranes and promote membrane insertion and disruption

A

Cathelicidins

91
Q

Y/N: The chemotactic activities of different types of antimicrobial proteins are distinct from one another, and each recruits different types of cells

92
Q

Y/N: Full-term newborn babies have a well-developed and functional skin barrier at birth

93
Q

Infant skin has a (thinner/thicker) stratum corneum with (low/high) levels of natural moisturizing factors and (lesser/greater) transepidermal water loss compared with adult skin

A

Thinner
Low
Greater

94
Q

Transepidermal water loss in healthy full-term newborns at birth is (lower/equal to/greater) than that of adult skin

A

Equal to or lower

95
Q

Formation of the fetal biofilm vernix caseosa during the

A

Third trimester

96
Q

Protects the epidermis from amniotic fluid and facilitates formation of the stratum corneum beneath it

A

Vernix caseosa

97
Q

Vernix (retension/removal) after birth has been reported to result in greater skin hydration and a lower skin surface pH at 24 hours after birth

98
Q

Babies born before _____ weeks of gestation lack the covering of the vernix

99
Q

Babies delivered at _____ weeks of gestation have only a few layers of stratum corneum

100
Q

Babies delivered before _____ weeks of gestation lack the stratum corneum

101
Q

Y/N: The transepidermal water loss of extremely preterm infants is significantly higher than that of full-term infants even at 1 month after delivery

102
Q

Preterm newborn/full-term newborn/infant/ adult:

NMFs high in the vernix caseosa

A

Full-term newborn

103
Q

Preterm newborn/full-term newborn/infant/ adult:

NMFs low in the stratum corneum

104
Q

Preterm newborn/full-term newborn/infant/ adult:

NMFs high in the stratum corneum

105
Q

Preterm newborn/full-term newborn/infant/ adult:

High surface pH

A

Full-term newborn

106
Q

Preterm newborn/full-term newborn/infant/ adult:

Low surface pH

A

Infant

Adult

107
Q

Preterm newborn/full-term newborn/infant/ adult:

High sebum

108
Q

Preterm newborn/full-term newborn/infant/ adult:

Low sebum

109
Q

Preterm newborn/full-term newborn/infant/ adult:

High stratum corneum water content

110
Q

Preterm newborn/full-term newborn/infant/ adult:

Low stratum corneum water content

111
Q

Preterm newborn/full-term newborn/infant/ adult:

Low dermal collagen fiber density

112
Q

Preterm newborn/full-term newborn/infant/ adult:

High dermal collagen fiber density

113
Q

Preterm newborn/full-term newborn/infant/ adult:

High rate of water absorption

114
Q

Preterm newborn/full-term newborn/infant/ adult:

Low rate of water absorption

115
Q

Preterm newborn/full-term newborn/infant/ adult:

Very high to high TEWL

A

Preterm newborn

116
Q

Preterm newborn/full-term newborn/infant/ adult:

Low TEWL

A

Full-term newborn

Adult

117
Q

Preterm newborn/full-term newborn/infant/ adult:

High TEWL

118
Q

Barriers against UV stresses at the stratum corneum:
_____ at the air-skin interface
Absorption by _____
Diffraction via _____

A

Reflection
Trans-urocanic acid
Keratin filaments

119
Q

In the viable cell layer of the epidermis, _____ is the major factor that absorbs UV irradiation

120
Q

In humans, cooling is mainly achieved by the

A

Evaporation of water secreted from eccrine sweat glands

121
Q

Human skin has the (lowest/highest) reported density of eccrine sweat glands among all mammals

122
Q

When the body temperature (lowers/rises), skin surface blood vessels are dilated, and the skin appears red

123
Q

In (cold/hot) air, the skin turns pale because blood vessels contract to decrease blood flow

124
Q

Mechanism by which the core body temperature is maintained under conditions of extreme cold or heat in homothermic animals

A

Vascular concurrent heat exchange

FD9 (108 decks)

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