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MK ACVD Exam > Dermis, adnexa and collagen > Flashcards

Dermis, adnexa and collagen Flashcards

1
Q

Describe the secretory function of sebaceous glands

A

Holocrine- cells burst and release full contents into ducts

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2
Q

Describe the secretory function of eccrine (atrichial) sweat glands

A

Merocrine- secrete product via exocytosis

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3
Q

Where do sebaceous glands empty their contents?

A

Into the hair follicle canal

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4
Q

Where do epitrichial glands empty their contents?

A

Into the hair follicle canal

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5
Q

Where do eccrine (atrichial) glands empty their contents?

A

Directly onto the skin

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6
Q

On what parts of the body are sebaceous glands larger and more numerous?

A

Mucocutaneous junctions, interdigital spaces, rump, chin, dorsal tail

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7
Q

What 2 parts of the body do NOT contain sebaceous glands?

A

Paw pads, nasal planum

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8
Q

What are the two types of sweat glands?

A

Epitrichial, atrichial (eccrine)

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9
Q

Define merocrine secretion

A

Secretory vesicles travel to apical surface of cell, fuse with plasma membrane, and release secretion into extracellular space (no part of cell is lost)

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10
Q

Define apocrine secretion

A

Secretory products accumulate at the apical portion of the cell and are released by pinching off some of the plasma membrane and cytoplasm (top of the cell is lost)

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11
Q

Define holocrine secretion

A

Secretory products accumulate at apical end of cell and the cells undergoes apoptosis and disintegration, releasing the secretory products and cell debris (whole cell is lost)

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12
Q

What is contained within horse sebum that isn’t found in other species’ sebum?

A

Lactones

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13
Q

What is the effect of estrogens on sebaceous glands?

A

Involution

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14
Q

What is the effect of glucocorticoids on sebaceous glands?

A

Involution

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15
Q

What is the effect of androgens on sebaceous glands?

A

Hypertrophy/hyperplasia

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16
Q

What is the effect of retinoids on sebaceous gland secretion?

A

Reduced sebum production

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17
Q

Describe the secretion of epitrichial sweat glands

A

Merocrine (though historically classified as apocrine, this is incorrect)

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18
Q

Where are epitrichial sweat glands found in the skin?

A

All haired skin, adjacent to primary hair follicles and deep to sebaceous glands
- not present on paw pads or nasal planum

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19
Q

What is the relationship between epitrichial sweat gland size and hair density?

A

These glands are larger in areas with less hair

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20
Q

On what parts of the body are epitrichial sweat glands larger and more numerous?

A

Mucocutaneous junctions, interdigital spaces, chin, rump, dorsal tail (same as sebaceous glands)

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21
Q

What glands are lacking in rodents and ferrets?

A

Epitrichial sweat glands

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22
Q

Where are epitrichial sweat glands found in rabbits?

A

Around the lips ONLY

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23
Q

What glands are lacking in horses?

A

Atrichial sweat glands

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24
Q

What type of gland are the circumanal/hepatoid glands?

A

Modified sebaceous glands

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25
Q

What is the primary sweat gland in horses?

A

Epitrichial gland

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26
Q

Which signals promote the development of sebocytes/sebaceous glands from stem cells?

A

Shh, Myc

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27
Q

Which signal inhibits the development of sebocytes/sebaceous glands?

A

Wnt

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28
Q

What special stain could be used to highlight lipid?

A

Oil red O

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29
Q

What receptors on sebaceous glands help accumulate lipid from the circulation?

A

LDL (low density lipoprotein), FATP4 (fatty acid transporter 4)

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30
Q

What type of gland is affected in equine anhidrosis?

A

Epitrichial sweat glands

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31
Q

What stain could you use to highlight epitrichial gland ducts and acini?

A

Cytokeratin

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32
Q

What is the mode of inheritance of sebaceous adenitis in poodles and Akitas?

A

Autosomal recessive

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33
Q

What conditions could potentially be associated with sebaceous adenitis?

A

Leishmaniasis
Hypothyroidism

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34
Q

What equine breeds are at increased risk of anhidrosis?

A

Warmbloods
Thoroughbreds

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35
Q

Describe the pathogenesis of equine anhidrosis

A

Continuously high levels of epinephrine leads to desensitization and downregulation of aquaporin-5 receptors and degeneration of secretory cells

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36
Q

What class of antibiotics has been associated with anhidrosis in horses?

A

Macrolides (especially erythromycin)

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37
Q

How do you test for anhidrosis in horses?

A

Intradermal injection of epinephrine or another beta-2 agonist (i.e. terbutaline)–> anhidrotic horse only sweats at the highest concentration(s) and only several hours after injection

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38
Q

What is the developmental origin of the dermis?

A

mesoderm

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39
Q

Where is the dermis the thickest?

A

Haired skin

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40
Q

What are the primary cells that form dermal fibers?

A

Fibroblasts

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41
Q

What type of fiber makes up the majority of the dermal ECM?

A

Collagen

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42
Q

What special stain would highlight collagen?

A

Maisson trichrome (collagen stains blue)

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43
Q

What collagen types predominate in the dermis?

A

1, 3, 5

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44
Q

What type of collagen is prevalent in wound healing and in fetal skin?

A

Type III

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45
Q

What type of collagen is a major component of anchoring fibrils?

A

Type VII

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46
Q

Where does collagen synthesis begin?

A

Within fibroblasts (on the rough ER)

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47
Q

What occurs to proline and lysine in the rough ER?

A

They are hydroxylated into hydroxyproline and hydroxylysine

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48
Q

What enzymes hydroxylate proline and lysine?

A

Prolyl and lysyl hydroxylase

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49
Q

What factor is the hydroxylation of proline and lysine dependent upon?

A

Ascorbic acid (vitamin C)

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50
Q

What occurs to hydroxylysine once it is released from the rough ER?

A

it is glycosylated

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51
Q

In what form is collagen secreted out of the fibroblast?

A

Pro-collagen

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52
Q

What is the final step in pro-collagen formation?

A

3 pro-alpha chains twist to form a triple helix

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53
Q

What does collagen become right after it is secreted as procollagen?

A

Tropocollagen

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54
Q

What enzyme is critical to transform procollagen to tropocollagen?

A

Procollagen peptidase

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55
Q

What enzyme links tropocollagen molecules to form collagen fibrils?

A

Lysyl oxidase

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56
Q

What metal is necessary for normal functioning of lysyl oxidase?

A

Copper

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57
Q

What protein is excreted in urine and can serve as a marker of collagen degradation?

A

Hydroxyproline

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58
Q

What enzyme involved in collagen synthesis is inhibited by glucocorticoids?

A

Prolyl hydroxylase

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59
Q

What is the effect of TGF-B on collagen synthesis?

A

Stimulatory

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60
Q

What is the effect of IL-1 on collagen synthesis?

A

Stimulatory

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61
Q

What is the effect of bleomycin on collagen synthesis?

A

Stimulatory

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62
Q

What is the effect of IGF 1+2 on collagen synthesis?

A

Stimulatory

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63
Q

What is the effect of vitamin D3 on collagen synthesis?

A

Inhibitory

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64
Q

What is the effect of PGE2 on collagen synthesis?

A

Inhibitory

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65
Q

What is the effect of IFN-gamma on collagen synthesis?

A

Inhibitory

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66
Q

What is the effect of TNF-a on collagen synthesis?

A

Inhibitory

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67
Q

What special stain can highlight elastin?

A

Verhoeff van Gieson

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68
Q

What special stain can highlight reticulin fibers?

A

Silver

69
Q

What is a proteoglycan?

A

A protein covalently linked to a glycosaminoglycan

70
Q

Name 4 types of glycoproteins

A

Fibronectin
Proteoglycan
Tenascin
Mucin

71
Q

What enzyme has increased synthesis by dermal fibroblasts, resulting in increased mucin in Shar Peis

A

Hyaluronan synthase 2

72
Q

What is the major proteoglycan found in the dermis?

A

Versican

73
Q

What cells synthesize glycoproteins in the dermis?

A

Fibroblasts

74
Q

Which IHC stains can distinguish dermal dendrocytes from Langerhans cells?

A

Dermal dendrocytes are CD4+, CD90+

75
Q

What proteases may be contained within mast cells?

A

Tryptase, chymase, or both

76
Q

What are the primary cell types in the dermis?

A

Fibroblasts
Dermal dendrocytes
Melanocytes
Mast cells
Lymphocytes (low #)

77
Q

What is the major type of vessel in the dermis?

A

Post-capillary venules

78
Q

What is the physiologically reactive segment of the dermal microcirculation?

A

Post-capillary venules

79
Q

Where would you find Weibel-Palade bodies?

A

Within the endothelial cell cytoplasm

80
Q

What is the function of Weibel-Palade bodies?

A

Store VWF and P-selectin

81
Q

What is the function of pericytes?

A

Contractile cells which regulate capillary flow

82
Q

What are the slow-adapting mechanoreceptors in the skin?

A

Tylotrich pads
Ruffini corpuscle
Merkel cells

83
Q

What are the fast-adapting mechanoreceptors in the skin?

A

Meissner’s corpuscle
Pacinian corpuscle
Tylotrich HAIR

84
Q

What does a Meissner’s corpuscle sense?

A

low-frequency vibration
touch

85
Q

What does a Pacinian corpuscle sense?

A

High-frequency vibrations
touch

86
Q

What does a Ruffini corpuscle sense?

A

Stretch

87
Q

What does a Merkel cell sense?

A

Pressure
Edges
Curves

88
Q

What is mutated in Ehlers-Danlos syndrome?

A

Type I or III collagen

89
Q

What is the genetic defect in Ehlers-Danlos syndrome?

A

Lysyl hydroxylase

90
Q

What condition is characterized by cigarette paper scars?

A

Ehlers-Danlos/HERDA

91
Q

How do you calculate the skin extensibility index?

A

(Vertical height of skin fold/body length) x 100

92
Q

What skin extensibility index is abnormal in dogs?

A

> 14.5%

93
Q

What skin extensibility index is abnormal in cats?

A

> 19%

94
Q

True or false: HERDA skin does not heal readily

A

False (but causes cigarette paper scars)

95
Q

What special stains can be used to highlight mucin?

A

Alcian Blue
PAS
Mucicarmine

96
Q

What are the components of the extracellular matrix?

A

Collagen
Elastin
Microfibrillar proteins
Fibronectin
Proteoglycans

97
Q

What is the key role of collagen in the dermis?

A

Tensile strength (resistance to stretch)

98
Q

What is the amino acid structure of type I collagen?

A

Glycine-X-Y (X usually proline, Y usually hydroxyproline)

99
Q

How does the AA content of type III collagen differ from that of type I?

A

Type III collagen has a cysteine residue in addition to glycine and lots of hydroxyproline

100
Q

What type of collagen is found within hemidesmosomes and anchoring filaments, attaching the basal keratinocyte to the basement membrane?

A

Collagen XVII (BPAG2)

101
Q

What is another name for collagen XVII?

A

BPAG2

102
Q

What type of collagen forms anchoring fibrils?

A

Type VII

103
Q

What 2 collagens are necessary for cohesion of the epidermis and dermis?

A

Collagen VII - attaches BM to dermal ECM
Collagen XVII - attaches basal keratinocytes to lamina densa

104
Q

What molecule is crucial for the folding of collagen and its triple helix structure?

A

Hydroxyproline (specifically trans-4-hydroxy-1-proline)

105
Q

What enzymes cleave the terminal ends of procollagen to form tropocollagen?

A

Procollagen N-proteinase (removes amino terminal)
Procollagen C-proteinase (removes carboxy terminal)
(procollagen peptidases)

106
Q

What is the mutation in HERDA?

A

missense mutation in cyclophilin B (PPIB gene) –> glycine is substituted to arginine
–PPIB is important for normal collagen folding

107
Q

How does UV radiation impact HERDA?

A

UV –> upregulation of collagenase genes (esp matrix metalloproteinase 1) –> thin skin especially on dorsum

108
Q

What is the effect of retinoids on collagen production?

A

Inhibitory OR stimulatory

109
Q

What mineral do matrix metalloproteinases require for their activity?

A

Calcium

110
Q

What collagens does MMP-1 break down?

A

I, III, VII

111
Q

What are desmosines?

A

Covalent cross-links that make elastic fibers insoluble

112
Q

Is hydroxylysine present in elastic fibers?

A

No

113
Q

What is the major function of the dermal ground substance?

A

Hydration

114
Q

What do glycosaminoglycans bind in order to provide hydration?

A

Ions and water

115
Q

Where would perlecan be found in the skin?

A

All basement membranes

116
Q

What is the specific mutation in the autosomal dominant form of Ehlers-Danlos in dogs?

A

COL5A1

117
Q

What is the mutation in dermatosparaxis?

A

ADAMTS-2 (aka procollagen N-proteinase)

118
Q

What element do the matrix metalloproteinases contain?

A

Zinc

119
Q

Which MMPs degrade collagen I to collagen III?

A

Interstitial collagenases (MMP-1, MMP-8, MMP-13)

120
Q

What is the effect of IL-1 on MMP activity?

A

Increases MMP

121
Q

In which vessels of the microcirculation do inflammatory cells migrate out of the vasculature and into tissue?

A

Post-capillary venules

122
Q

In what type of vessels would you find tight junctions?

A

Arterioles and capillaries

123
Q

What type of junction is present in postcapillary venules?

A

Adherens junctions (allows for passage of macromolecules)

124
Q

Are sinus hairs slow-adapting or fast-adapting?

A

Slow-adapting

125
Q

Besides the face, where would you find vibrissae in cats?

A

Palmar aspect of carpus

126
Q

What type of mechanoreceptor is located near a sinus hair follicle?

A

Pacinian corpuscle

127
Q

What types of nerves detect painful touch?

A

High-threshold C fibers and Alpha-delta nerve fibers

128
Q

What type of nerve fibers are the largest and most heavily myelinated?

A

Alpha-beta/type II fibers

129
Q

What is the most abundant type of somatosensory neuron?

A

C/type IV fibers

130
Q

What type of somatosensory neuron is unmyelinated?

A

C/type IV

131
Q

What type of nerve fiber responds to pruritogens?

A

C/type IV

132
Q

What type of nerve fiber has a slow conduction velocity?

A

C/type IV

133
Q

Through which part of the spinal cord do afferent sensory nerves travel to deliver pain/pruritus signals?

A

Dorsal root ganglion

134
Q

How does nerve growth factor promote itch?

A

It upregulates other neuropeptides (esp substance P and TRPV1)

135
Q

What type of opioids induce itch?

A

mu-receptor agonists

136
Q

What type of opioids reduce itch?

A

kappa-receptor agonists (and mu antagonists)

137
Q

What cells produce kallikreins?

A

WBC
KCs
Mast cells
Endothelial cells
Platelets

138
Q

What type of cell secretes TSLP?

A

KCs

139
Q

What type of T-cell response is promoted by TSLP?

A

Th2

140
Q

What cytokines are known to be pruritogens?

A

IL-2
IL-4
IL-13
IL-31
IL-33
TSLP

141
Q

What cells produce PGE2?

A

nerve fibers, KCs, mast cells

142
Q

What viral disease in cats is associated with facial pruritus?

A

Herpes

143
Q

What dog breeds are predisposed to inherited sensory neuropathies resulting in self-mutilation?

A

English Pointers (paws), Long-haired dachshunds (penis)

144
Q

What neuropathic disorders could cause tail-biting in dogs?

A

Cauda equina syndrome
Tail dock neuroma
Lumbosacral stenosis

145
Q

What cat breed is predisposed to tail-sucking?

A

Siamese

146
Q

What breed is predisposed to flank sucking?

A

Doberman

147
Q

Is chronic itch primarily histaminergic or non-histaminergic?

A

Non-histaminergic (so antihistamines don’t work very well)

148
Q

Edema in urticaria is limited to what layer of the skin?

A

Dermis

149
Q

Besides skin hyperextensibility, which other clinical signs might be seen with Ehlers-Danlos syndrome?

A

Joint laxity

150
Q

How does cutis laxa differ from Ehlers-Danlos clinically?

A

Ehlers-Danlos: fragile skin, maintains elastic recoil
Cutis laxa: flaccid but no cutaneous fragility, lacks elastic recoil

151
Q

What type of stain will highlight elastic fibers in the dermis?

A

Verhoeff

152
Q

What type of stain will highlight elaunin AND elastic fibers in the dermis?

A

Weigert

153
Q

What type of stain will highlight elaunin, elastic, AND oxytalan fibers in the dermis?

A

Oxidized Weigert

154
Q

What mutation occurs in Marfan syndrome in cattle?

A

FBN1 (fibrillin 1)

155
Q

What is the main clinical difference between Ehlers-Danlos and cutis laxa?

A

Ehlers-Danlos skin: hyperextensible skin which snaps back when tented
Cutis laxa: excessive skin and hyperextensible but will not snap back when tented

156
Q

This is a picture from a draft horse. Based on the radiograph, what is a top differential?

A

Chronic progressive lymphedema

157
Q

Describe the pathogenesis of solar elastosis

A

UV exposure –> cytokine expression –> neutrophil infiltration –> MMP and elastase release and ECM damage –> attempted repair via secretion of elastic fiber components

158
Q

What is the cause of erythema ab igne?

A

Chronic exposure to radiant heat source

159
Q

Does erythema ab igne usually ulcerate, crust, and/or scar?

A

No (think vasculopathy or burn if you see these signs)

160
Q

True or false: hepatoid glands are not present in cats

A

True

161
Q

What gene is mutated in Shar Pei mucinosis?

A

HAS2

162
Q

What gene is mutated in Ehlers-Danlos syndrome in cats?

A

COL5A1

163
Q

Which proteinase resides within neutrophil granules and degrades predominantly collagen I and III upon release?

A

MMP-8

164
Q

What cytokine is a major stimulator of elastin production?

A

TGF-B

165
Q

During the formation of a proteoglycan, which amino acid residue does the glycosaminoglycan bind to within the protein core?

A

Serine

166
Q

True or false: epitrichial glands are involved in thermoregulation

A

False

167
Q

What is the necessary signal pathway for development of sebocytes?

A

SOX9

168
Q

What stain could you use to highlight amyloid?

A

Congo Red

MK ACVD Exam (17 decks)

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