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Flashcards in 4.1 lect - connective tissue - Rushmore Deck (200)
1

these stem cells are responsible for generating connective tissue within the body

mesenchymal stem cells

2

this type of collagen can be stronger than steel

type I collagen

3

collagen biosynthesis begins with...

transcription and translation of alpha chains

4

how many different collagen alpha chains are possible?

42

5

how many different collagen types are possible?

28 and counting

6

how are collagen types named?

by order of discovery

7

T/F collagen is a protien

true

8

every third amino acid in collagen I is __

glycine

9

collagen I contains large ratios of these three amino acids

glycine
proline
lysine

10

how often does glycine occur in collagen I ?

every third amino acid

11

after transcription and translation of alpha chains, what is next in collagen I biosynthesis?

post-translational modification in the ER
-glycosylations
-hydroxylations (hydrosyproline, hydroxylysine)

12

what are common post-translational modifications to collagen I ?

glycosylations
hydroxylations
-hydroxyproline
-hydroxylysine

13

when post-translational modifications in the ER is complete, the collagen I protein is called __

procollagen

14

how many alpha chains are in a procollagen molecule

3

15

why is procollagen called a triple helix?

it is composed of 3 alpha chains wound around each other

16

what is the role of glycine in procollagen?

allow tight winding

17

what is the role of hydroxyproline in procollagen?

bind alpha chains together

18

what regions make up the ends of procollagen?

propeptide regions (frayed rope)

19

after post-translational modification in the ER, what is next for procollagen?

-secretion into extracellular space
-cleavage of propeptide regions by procollagen peptidase
-procollagen is now tropocollagen

20

where is procollagen formed?

in the ER

21

where is tropocollagen formed?

in the extracellular space

22

what does procollagen become in the extracellular space?

tropocollagen

23

this enzyme cleaves the propeptide regions from procollagen

procollagen peptidase

24

this enzyme turns procollagen into tropocollagen

procollagen peptidase

25

procollagen peptidase

cleaves propeptide regions from procollagen, turning it into tropocollagen in the extracellular space

26

how does procollagen become tropocollagen?

it is secreted into the extracellular space, where procollagen peptidase cleaves the propeptide regions from its ends, turning it into tropocollagen

27

what is the function of the propeptide regions of procollagen?

prevent polymerization intracellularly

28

after cleavage of procollagen into tropocollagen, what is next for the protein?

it polymerizes into collagen fibrils

29

the secondary folding structure of alpha collagen chains is __

helical

30

how is one alpha collagen chain associated with the other?

through hydroxyproline interactions

31

how does one tropocollagen protein associate with another?

through hydroxylizine interactions

32

the role of hydroxyproline in collagen I biosynthesis is to...

associate three alpha chains together

33

the role of hydroxylysine in collagen I biosynthesis is to...

polymerize tropocollagen proteins together

34

in two words or less per step, describe the biosynthesis of collagen I in 6 steps

1. transcription/translation
2. post-translational modification
3. procollagen
4. tropocollagen
5. collagen fibrils
6. collagen fibers

35

where do the following steps in the biosynthesis of collagen I take place?
1. transcription/translation
2. post-translational modification
3. procollagen
4. tropocollagen
5. collagen fibrils
6. collagen fibers

1. nucleus / RER
2. ER
3. ER
4. extracellular space
5. extracellular space
6. extracellular space

36

what do collagen I fibrils look like on LM?

collagen fibrils are not resolvable on LM, only fibers

37

what color do collagen fibers stain on H&E ?

pink - acidic / eosinophilic

38

what is the difference between a fibril and a fiber?

fibrils make up fibers

39

3 components of connective tissue are:

-cells
-fibers
-ground substance

40

large cells that store lipids and often occur together in large masses

unilocular adipocytes

41

adipose tissue is composed of...

adipocytes

42

white fat cells are also called...

unilocular adipocytes

43

unilocular adipocytes are also called...

white fat cells

44

lipid storing cells specialized for heat production

multilocular adipocytes
(brown fat cells)

45

multilocular adipocytes are...

lipid storing cells specialized for heat production

46

another name for multilocular adipocyte

brown fat cell

47

another name for brown fat cells

multilocular adipocytes

48

this cell is responsible for the production, remodeling, and degradation of the extracellular matrix fibers and ground substance

fibroblasts

49

fibroblasts

produce, remodel, and degrade extracellular matrix fibers and ground substance

50

myofibroblasts

subtypes of fibroblasts that produce myosin in order to generate force

51

this is a myosin-producing subtype of fibroblast specialized to generate force

myofibroblast

52

what is the dominant fiber of connective tissue?

type I collagen

53

in what kinds of cells is procollagen synthesized?

fibroblasts

54

this type of collagen is synthesized as as triple-helix procollagen molecules within fibroblasts, then aligned and cross-linked extracellularly into fibrils

type I collagen

55

reticular fibers are made of this type of collagen

type III collagen

56

T/F type III collagen has a space filling function

false - type III collagen composes reticular fibers, which are small and do not have a space filling function (scaffolding function)

57

these fibers are found everywhere stretchiness is required

elastic fibers

58

elastic fibers are composed of...

elastin
fibrillin

59

elastin composes what type of connective tissue fiber?

elastic fibers (with fibrillins)

60

fibrillins compose what type of connective tissue fiber?

elastic fibers (with elastin)

61

what collagen types are associated with basement membranes and external membranes?

types IV and VII

62

type IV collagen is found...

forming a meshwork of dimers to form the basal lamina or external lamina

63

type VII collagen is found...

in the lamina retucularis, securing fibers of connective tissue (e.g. reticular fibers) to the basal lamina

64

this collagen type is crucial to the structure of cartilage

type II

65

type II collagen

is crucial to the structure of cartilage

66

this collagen type is found in the growth plates of bones

type X

67

briefly describe the functions of the following types of collagen:
I
II
III
IV
VII
X

I - tensile strength, space filler
II - cartilage
III - reticular fibers (scaffolding)
IV - meshwork of basal and external lamina
VII - secure ct fibers to basal lamina
X - growth plates

68

space between connective tissue cells and fibers is occupied by...

ground substance

69

ground substance consists of...

glycosaminoglycans (GAGs)
proteoglycans
glycoproteins
(highly hydrated complexes)

70

what is a proteoglycan

a core protein with one or more covalently attached GAG chains

71

the purpose of ground substance is to...

keep the ECM hydrated

72

classification and function of tissues are derived from...

the morphology of aggregated cells and their specializations

73

Connective tissues are comprised of...

cells surrounded by extracellular material

74

this tissue gives rise to all connective tissues of the adult

mesenchymal tissue

75

this is comprised of interconnected and multipotent cells derived from the mesoderm

mesenchymal tissue

76

T/F undifferentiated mesenchymal stem cells persist in the adult

true - they look like fibroblasts

77

3 classes of connective tissue proper

loose (areolar)
dense irregular
dense regular

78

areolar connective tissue is another name for

loose connective tissue

79

is loose connective tissue regular or irregular?

irregular

80

what is another name for connective tissue proper?

general connective tissue

81

what is another name for general connective tissue?

connective tissue proper

82

these two types of connective tissue exist on the same spectrum

loose (areolar)
dense irregular

83

how can you tell loose and dense irregular connective tissue apart?

according to fibrous content
-loose: many cells, few fibers, much ground substance
-dense: many fibers, few cells, little ground substance

84

this connective tissue is characterized by tightly packed fibers organized in one direction

dense regular connective tissue

85

3 examples of dense regular connective tissue include:

tendons - muscle to bone
ligaments - bone to bone
aponeuroses - muscle to muscle

86

a tendon connects...

muscle to bone

87

a ligament connects

bone to bone

88

an aponeurosis connects...

muscle to muscle

89

this connects bone to bone

ligament

90

this connects bone to muscle

tendon

91

this connects muscle to muscle

aponeurosis

92

what does dense regular tissue look like in the longitutinal plane? transverse?

-longitudinal: 1 directionally organized sometimes waivy rows of much fiber and relatively few cells / nuclei
-transverse: fibers not especially apparent, just looks like regularly spaced nuclei in a plain eosinophilic fascilcle

93

4 examples of specialized connective tissue include:

adipose tissue
blood
bone
cartilage

94

the two larges divisions of connective tissues are:

connective tissue proper (general)
specialized connective tissue

95

loose, dense irregular, and dense regular are subclasses of what larger class of connective tissue

connective tissue proper (general)

96

adipose tissue, blood, bone, and cartilage are subclasses of what larger class of connective tissue?

specialized connective tissue

97

what is the resident cell of loose connective tissue

fibroblast

98

what is the resident cell of dense irregular connective tissue

fibroblast

99

what is the resident cell of dense regular connective tissue

tendinocyte (a specialized fibroblast, more squished)

100

the resident cell of adipose tissue

adipocyte

101

the resident cell of bone

osteocyte

102

the resident cell of cartilage

chondrocyte

103

fibroblast

creates, elaborates, maintains, and degrades the ECM of loose and dense irregular connective tissue

104

tendinocyte

creates, elaborates, maintains, and degrades the ECM of dense regular connective tissue

105

adipocyte

creates, elaborates, maintains, and degrades the ECM of adipose tissue

106

osteocyte

creates, elaborates, maintains, and degrades the ECM of bone

107

chondrocyte

creates, elaborates, maintains, and degrades the ECM of cartilage

108

when is connective tissue not made from fibroblasts or other connective tissue resident cells?

-epithelial cells make basement membrane
-smooth muscle cells in walls of blood vessels make ECM elements
-Schwann cells make connective tissue elements in nervous tissue

109

what kind of cell makes the basement membrane?

epithelial cells

110

what kind of cells make connective tissue elements in nervous tissue?

Schwann cells

111

what is the shape of a fibroblast?

fusiform and flattened nucleus
long cytoplasmic process

112

what kinds of fibers can make up extracellular material?

collagen
reticular fibers
elastic fibers

113

what does ground substance look like on LM?

empty space

114

what does ground substance look like on EM?

spots / freckles

115

what is the ~diameter of a collagen fiber?

2-10 microns

116

how does the tensile strength of collagen compare to steel?

10x the strength

117

reticular fibers provide...

a flexible scaffolding

118

where are reticular fibers found?

in the stroma of regions and organs that change in volume e.g. lymph nodes, spleen, liver

119

what is the ~diameter of reticular fibers?

<2 microns

120

how does the diameter of reticular fibers compare to that of collagen fibers?

<2 microns vs 2-10 microns

121

how do reticular fibers stain?

argyrophilic
black with silver salts

122

which fiber stains argyrophobic black with silver salts?

reticular fibers

123

elastic fibers are specialized to...

allow distensibility
stretching of tissues with subsequent return to original form

124

this fiber is specialized to allow distensibility

elastic fiber

125

of collagen, reticular, and elastic fibers, which is the thinnest?

elastic (0.2 - 1.5 microns)

126

of collagen, reticular, and elastic fibers, which is the thickest?

collagen (2-10 microns)

127

what are the ~diameters of the following fibers:
-collagen
-reticular
-elastic

2-10 microns
<2 microns
0.2-1.5 microns

128

elastic fibers selectively stain with...

deep purple with
Vaerhoeff's stain or
resourcin-fuschin

129

how to tell difference between silver and vaerhoeff's stain?

-silver reticular fibers hold cells together in a framework, scaffolding (highly cellular)
-vaerhoeff elastic fibers do not associate with cells, merely hold together structures and permit stretching (fewer cells)

130

you would expect highly cellular material with connective tissue consisting of this fiber

reticular

131

you would expect few cells with connective tissue consisting of this fiber

elastin

132

what do collagen fibrils look like on EM?

small cylindrical structures aggregated into a much larger fibers

133

T/F type I collagen fibers are visible on LM

true

134

type I collagen accounts for __% of all collagens

90%

135

which connective tissue fiber is resistant to stretch?

type I collagen

136

T/F type II collagen organizes into scattered fibers

false - type II collagen (cartilage) does not organize into fibers

137

what is the composition of cartilage?

50% cartilage II
50% ground substance

138

what does type II collagen look like on EM?

scattered little fibers -- type II fibers do not organize into fibers but EM cannot make sense of their arrangement

139

this fiber has a high number of glycosylated residues with adjacent hydroxylated groups

reticular fiber (collagen III)

140

this fiber type allows the large changes in volume typical in tissues like adipose, hematopoeitc, and lympoid tissues

reticular fiber

141

this collagen type forms a meshwork of dimers to form the external or basal lamina

type IV collagen

142

this collagen type forms anchoring fibers in the lamina reticularis that secure fibers of connective tissue (e.g. reticular fibers) to the basal lamina

type VII collagen

143

give 2 examples of collagenopathies

scurvy
ehlers-danlos syndrome

144

how does scurvy arise?

-not enough vitamin C ingested for proline and lysine hydroxylation
-ulcers/disruption of epithelial surfaces, teeth fall out (regions of high collagen turnover most affected)

145

what parts of the body does scurvey effect most?

regions of high collagen turnover (e.g. periodontal ligament)

146

Ehles' Danlos Syndrome is characterized by

prevalent dislocation, hyperextension

147

this collagenopathy is characterized by prevalent dislocation and hyperextension

Ehler's Danlos Syndrome

148

elastic fibers usually occur with __ to prevent overstretching

collagen

149

what is fibroelastic collagen?

elastic fibers occur with collagen fibers to allow stretching but prevent over stretching

150

what is the structure of an elastic fiber?

an amorphous elastin core surrounded by microfibrils made of fibrillin

151

are elastic fibers hydrophobic or hydrophilic?

hydrophobic - tendency to curl up together in water

152

in elastic fibers, desmosine is a protein the functions to...

cross link elastic fiber molecules, regulating elasticity and providing structure

153

marfan syndrome

genetic defect in fibrillin (FBN1) gene
-affects eyes, heart, blood vessels
-patients are tall with long fingers and limbs (lincoln, volleyball player w/ burst aorta)

154

a genetic defect in the fibrillin (FBN1) gene causes this syndrome

marfan syndrome
-affects eyes, heart, blood vessels
-patients are tall with long fingers and limbs (lincoln, volleyball player w/ burst aorta)

155

non-fibrillar extracellular substance in the ECM is...

ground substance

156

T/F ground substance is comprised of materials that critically influence cell growth, movement, proliferation and differentiation

true

157

ground substance is comprised of these:

GAGs
proteoglycans
adhesive glycoproteins

158

T/F ground substance stains eosinophilic

false - it is typically washed out with standard histological preparative techniques

159

what are the general molecular and chemical characteristics of GAGs?

-long unbranched linear chains of <300 repeating disaccharide units
-one unit is an amino sugar that is sulfated and carboxylated (1-2 negative charges per repeating subunit, massive amounts of electronegativity)

160

what function to the dense negative charges of GAGs serve?

dense negative charges repel each other, making GAG matrix slippery, attracting water in hydration shells, making large and pliable volume resistive to compressive forces and allowing diffusion of nutrients and gases

161

4 typical GAGs include...

-dermatan sulfate
-heparan sulfate
-keratan sulfate
-chondroiotin sulfate

162

name 1 unique GAG, why is it unique?

hyaluronic acid
-non-sulfated
-can have up to 25000 repeates while other GAGs have no more than 300
spun from the cell membrane rather than synthesized within the cell like other GAGs

163

this GAG is unique because
-it is non-sulfated
-can have up to 25000 repeates while other GAGs have no more than 300
spun from the cell membrane rather than synthesized within the cell like other GAGs

hyalurnonic acid

164

the function of GAGs in ground substance

-charges repel each other making GAG chains slippery
-hydration shells cause large volume that enables a pliable medium to resist compressive forces
-hydration allows diffusion of nutrients and gases
-web of GAGs makes difficult for pathogens to navigate
-permit use of signaling molecules

165

one dermatan sulfate molecule attracts...

2 H2O
2 Na+
hydration shells cause large volume that enables a pliable medium to resist compressive forces and allows diffusion of nutrients and gases

166

how do GAGs allow diffusion of nutrients and gases?

hydration of ECM
-GAGs are carboxylated and/or sulfonated
-charges repel each other making GAG chains slippery
-hydration shells cause large volume that enables a pliable medium to resist compressive forces
-hydration allows diffusion of nutrients and gases

167

what is a proteoglycan?

a protein with one or more covalently attached GAG chains
-occupy large volumes relative to mass
-resist compressive forces
-hydrate matrix for gas and nutrient transport
-modifiable sieve that permits/restricts access to
substances based on charge and size
-permit use of signaling molecules

168

what is the function of proteoglycans in ground substance?

same as that of GAGs:
-occupy large volumes relative to mass
-resist compressive forces
-hydrate matrix for gas and nutrient transport
-modifiable sieve that permits/restricts access to
substances based on charge and size
-permit use of signaling molecules

169

how do neutrophils navigate proteoglycan tangles of ground substance?

secrete cathepsins and gelatinases to facilitate passage

170

neutrophils secrete these two enzymes to facilitate passage through proteoglycan tangles of ground substance

cathepsins
gelatinases

171

what type of cell secretes cathepsins and gelatinases to facilitate its passage through proteoglycan tangles of ground substance?

neutrophil

172

how do pathogenic bacteria navigate proteoglycan tangles of ground substance?

secrete hyaluronidase to break down hyaluronic acid

173

pathogenic bacteria can secrete this enzyme to facilitate passage through ECM

hyaluronidase

174

what is the difference between glycoproteins and proteoglycans?

proteoglycans - unbranched, repeating GAG subunits that hydrate
glycoproteins - 'glue' cells to fibers and glycoproteins. branched subunit

175

what is the function of glycoproteins in ground substance in the ECM?

'glue' together cells, fibers, and ground materials. sometimes help cells travel through matrix

176

name 3 places we have seen glycoproteins

-secretions (mucins)
-glycocalyx
-ground substance

177

which have larger sugar chains, glycoproteins or proteoglycans?

proteoglycans - larger, linear sugar chains

178

which have shorter sugar chains, glycoproteins or proteoglycans?

glycoproteins - smaller, branched sugar chains

179

give an example of an adhesive glycoprotein in ground substance

fibronectin
-attaches integrins of cell membranes to matrix elements (fibers and GAGs)
-enables cells to travel through matrix

180

fibronectin is an example of what element of ground substance?

a glycoprotein
-attaches integrins of cell membranes to matrix elements (fibers and GAGs)
-enables cells to travel through matrix

181

describe the differential appearance of unilocular and multilocular adipocytes

unilocular - one big lipid droplet, eccentrically displaced nucleus
miltilocular - multiple lipid droplets, nucleus is more round and central, eosinophilic mitochondria

182

what organelle and protein specialize multilocular adipocytes to generate heat?

mitochondria
thermogenin (uncoupling protein-1 (UCP-1))

183

where / when are multilocular adipocytes usually found?

-mostly found in human infants
-also found in human adults around scapulae and cervial/thoracic vertebral regions

184

brown fat was discovered in adults when a radiolabeled marker that is taken up and trapped in tissues with high metabolic rates was observed in brown fat under what conditions?

normal to cold conditions - brown fat metabolically activated

185

what kind of adipocytes give a "chicken wire" histological appearance?

unilocular adipocytes (white fat)

186

T/F white adipose tissue is highly vascular

true

187

what are 4 functions of white adipose tissue?

-mechanical absorption
-thermal insulation
-energy storage
-endocrine function

188

adipocytes release chemical signals called...

adipocytokines
e.g. leptin and adiponectin

189

leptin and adiponectin are examples of...

adipocytokines - chemical signals released by adipocytes

190

adipocytokines are...

chemical signals released by adipocytes

191

release of this adipocytokine is directly related to the amount of stored fat

leptin

192

a cytokine is...

a chemical signal

193

lipostatic theory of energy balance

signal from cell to brain says adipocytes are empty, need to eat more, increase apetite. When filled, cells signal brain to use energy. Thought if we could interfere with these cytokine signals we could decrease appetite and obesity. easier said than done because adipocytes are like little endocrine glands, secreting many signals

194

adipocytes were originally thought to be generated....

during a specific post-natal period, after which few or no additional adipocytes are generated

195

up to about 18-25% of BMI change are due to what kind of adipocytic growth

hypertrophic growth

196

after about 18-25% BMI change, further changes are due to what kind of adipocytic growth

hyperplasia / hypercellularity

197

what kind of obesity is associated with more severe symptoms, hypertrophic or hypercellular?

hypercellular

198

how are adipocytes generated?

from mesenchymal stem cells

199

what is the rate of adipocyte turnover?

about 10% / year die and are replenished by mesenchymal stem cells. this rate of turnover is constant

200

what are 5 potential avenues for obesity treatment?

-get UCP1 into white fat, converting it into brown fat and get it to burn itself off
-modulate adipocytokine levels (complicated because of vast number of signals)
-alter cell turnover rates
-controlled diet and exercise
-gut microbiota transplant