4.1 - Lecture - CT Flashcards

1
Q

Mesenchymal Stem Cell (MSC)

A

Gives rise to the cells that are responsible for generating connective tissue

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2
Q

Unilocular Adipocytes

A
  • also known as white fat cells
  • large cells that store lipids
  • often occur together in large masses as adipose tissue
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3
Q

Multilocular Adipocytes

A
  • lipid storing cells specialized for heat production

- occur primarily in neonates

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4
Q

Fibroblasts

A
  • responsible for production, remodeling , degradation of the extracellular matrix fibers and ground substance
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5
Q

Myofibroblasts

A
  • Myosin-producing subtype of fibroblasts

- specialized to generate force

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6
Q

Type I Collagen

A
  • the dominant fiber of connective tissue
  • synthesized as triple-helix procollagen molecules within fibroblast
  • synthesized inside of fibroblasts
  • extracellular are aligned + cross-linked into fibrils
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7
Q

Type III Collagen

A
  • known as reticular fibers
  • much smaller than collagen type I
  • do not have a space-filling function
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8
Q

Elastic Fibers

A
  • Composed of elastins and fibrillins

- found where stretchiness is required

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9
Q

Types IV and VII Collagen

A
  • Found within basement membranes
  • type IV is incorporated into/makes up a large portion of the lamina densa
  • Type VII forms rings in the lamina reticularis to connect with other cytoskeletal elements
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10
Q

Type II Collagen

A

Crucial to the structure of cartilage

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11
Q

Type X Collagen

A

Found in the growth plate of bones

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12
Q

Ground Substance

A

= the space between connective tissue cells and fibers

  • consists of highly hydrated complexes of glycosaminoglycans, proteoglycans, glycoproteins
  • has extracellular long-chain proteins that keep ECM hydrated by binding water in lg. quantities
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13
Q

Glycosaminoglycans

A
  • part of the highly hydrated complexes making up the ground substance
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14
Q

Proteoglycans

A
  • have large sugar chains

- repeating units of the sugar chains

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15
Q

Glycoproteins

A
  • have seen before as secretions (mucins) or intergral membrane proteins (contributing to a glycocalyx)
  • also form component of ground substrates distinct from proteoglycansand fibers
  • sugar chains are much smaller than those found in proteoglycans
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16
Q

Hyaluronic Acid

A

= a typical glycosaminoglycan “backbone molecule”

  • organizes into numerous proteoglycan “core” molecules
  • each subunit consists of numerosu glycosaminoglycan chains which attract water
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17
Q

Dermatan Sulfate

A
  • a typical glycosaminoglycans
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18
Q

Heparan Sulfate

A
  • a typical glycosaminoglycan
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19
Q

Keratan Sulfate

A
  • a typical glycosaminoglycan
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20
Q

Chondroitin Sulfate

A
  • a typical glycosaminoglycan
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21
Q

3 components of connective tissue proper

A

1) loose (aveolar)
2) Dense irregular
3) Dense regular

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22
Q

4 specialized connective tissue types

A

1) adipose tissue
2) blood
3) bone
4) cartilage

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23
Q

Loose (aveolar) CT (irregular) contains:

A
  • Lots of ground substance (white space in lm)
  • lots of cells
  • very little fibers
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24
Q

Dense irregular CT contains:

A
  • lots of fibers (dominated by them in volume and function), the 3D organization of fibers to be ready for forces from all side
  • little ground substance space
  • little space for cells
25
Q

Dense Regular CT

A
  • tight packed fibers (organized in 1 direction)

- FXN : single force vector

26
Q

A tendon connects:

A

Muscle to bone

27
Q

A ligament connects:

A

bone to bone

28
Q

a aponeuroses connects:

A

muscle to muscle

29
Q

FXN of resident cells of CT

A

responsible for creating, elaborating, maintaining, degrading ECMatrix of CT

30
Q

Resident Cells of Loose, Dense Irregular, and Dense regular CT (and any technical nomenclature):

A

= Fibroblasts

- called tendenocytes in dense regular tissue (because of their extreme specialization that causes them to be squished)

31
Q

Resident cells of adipose tissue

A

Adipocytes

32
Q

Resident cells of bone

A

osteocytes

33
Q

Resident cells of cartilage

A

chondrocytes

34
Q

3 exceptions to the function of resident cells of CT

A

1) Epithelial Tissue - epithelial cells make the Ct of the basement membrane
2) Muscle tissue - smooth muscle cells in walls of blood vessel make the ECMatrix elements
3) Nervous Tissue - Schwann cells make CT element

35
Q

Describe the LM appearance of fibroblasts

A
  • fusiform + flattended nucleus

- long cytoplasmic processes

36
Q

3 main components of the ECM Fibers

A
  • collagen
  • reticular fibers
  • elastic fibers
37
Q

3 main components of ground substance

A
  • glycosaminoglycans
  • proteoglycans
  • adhesive glycoproteins
38
Q

Places where reticular fibers are commonly found

A
  • lymph node
  • spleen
  • liver
39
Q

2 Selective stains of elastic fibers

A
  • Verhoff’s Stain

- resourcin fuschin

40
Q

The key to Differentiating between reticular and elastic fibers:

A

Reticular fibers - hold cells together (lots of cellls present)

Elastic fibers - holding structure/tissue together

41
Q

Difference between EM/LM of collagens

A

Collagen Fiber = viewable in LM or EM

Collagen Fibril = viewable only in EM

42
Q

Type I Collagen

A
  • 90% of all collagens
  • fibrils assemble into fibers
  • high tensile strength + resistance to stretch
43
Q

Type II Collagen

A
  • only seen in cartilage
  • does not assemble into fibers
    = 50% type II collagen 50% ground substance (proteoglycans)
  • are not laid down in organized manner - do not see fibers in LM
44
Q

Type IV Collagen

A
  • Not fibrillar - propeptides not cleaved
  • does not display a typical periodicity
  • forms meshwork of dimers to form external/basal lamina
    = a very strong web of autopolymerized type IV collagen
45
Q

Type III Collagen

A

= main component of reticular fibers
- very high # of glycosylated residues with adjacent hydroxylated groups
- found in stroma of highly cellular tissues
(adipose, hematopoietic, lymphoid)
- enables large changes in volume normally seen in those organs

46
Q

Type VII collagen

A
  • anchoring fibers: forms sm. + lg. loops that the reticular fibers pass through
  • loops are formed with help of anchoring bodies/plaques to connect different strands of Type VII into circles
  • secure the fibers of CT to the basal lamina
47
Q

Describe the interplay of CT and the Basement Membrane

A
  • Laminin = connects lamina lucida with the lamina densa
  • lamina densa is largely composed of type IV collagen
  • Loops of type VII collagen extend down from lamina dense to form lamina reticular is + connect basement membrane to rest of CT (through the reticular fibers)
48
Q

Briefly Describe the clinical significance of collagen (collagenopathies) as they relate to Scurvy and Ehlers-Danlos Syndrome

A

Scurvy: lack of vitamin C - which is necessary for proline + lysine hydroxylations - causes ulcers + disruptions of epithelial surface due to lack of alpha chain binding (esp. in areas of high collagen turnover)

Ehlers-Danlos Syndrome: connection disorder resulting from to improper formation/ assembly of collagen

49
Q

Elastic Fibers are comprised of

A

fibrillin glycoprotein microfibrils surrounding an amorphous elastin core

50
Q

Elastin is

A
  • hydrophobic with very strong tendency to curl up due to hydrophobic forces (that can be overcome by force of stretch)
  • cross linking proteins in elastin = desmosine (regulates elasticity and provides structure)
51
Q

Marfan syndrome

A
  • genetic defect in Fibrillin (FBN1) gene
  • affects scaffolding of elastin fibers
  • affects: eyes, heart, blood vessels
    characteristic of patients = tall with long slender fingers and limbs
52
Q

Primary + most critical function of GAGs + Proteoglycans is:

A

hydration of the ECMatrix

53
Q

Hyaluronic Acid

A
  • Unique GAG
  • nonsulfated
  • can have up to 25,000 repeating units (others have <300)
  • is spun from cell membrane (others are synthesized w/n the cell)
54
Q

GAGs (glycosaminoglycans)

A
  • long, unbranched linear chains (<300 repeating disaccharide units)
  • each repeat has at least 2 (-) charges in the chain
  • 1 is an amino sugar - sulfated + carboxylated
  • contain massive amounts of electronegativity
55
Q

Proteoglycans

A
  • proteins with 1+ covalently attached GAG chains (more GAGs = larger hydration shell)
  • slippery + resist compressive forces
56
Q

Glycoproteins

A
  • glue together fibers, ground material, cells
  • branched, non-repeating units of sugars
  • multiple type of sugars
  • often v. short
57
Q

Fibronectin

A

= an adhesive glycoprotein

  • attached integrins of cell membranes to matrix elements (fibers of GAGs)
  • enables cells to tunnel through matrix
58
Q

Explain how presence + quantity of EC components (FIbers vs. ground substance) confers characteristic to tissues:

A

Fibers –> Strength, elasticity, flexibilty

Ground substance –> barrier FXN, hydration, anti-compressibilty

59
Q

Relate the changes of obesity to the changes in adipocytes

A

1st 15%-25% change in BMI is due to increase in size of adipocytes (hypertrophies)

Next changes (larger changes) in BMI are due to increases in # of adipocytes