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BMS2002 > L11 > Flashcards

L11 Flashcards

1
Q

what is cartilage

A

a specialized connective tissue

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2
Q

what are the types of cartilage

A

hyaline: ribs, nose, larynx, trachea, articular joints

fibro: joint capsules, ligaments

elastic: ear, epiglottis, larynx

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3
Q

what is the only type of cells found in cartilage

A

chondrocytes

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4
Q

what are the two key components found in articular cartilage

A

Collagen (type II) and aggrecan

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5
Q

what are Collagen (type II) and aggrecan important for

A

strength and support

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6
Q

what happens in Ehlers Danlos syndrome

A

defective deposition of collagen causing
hyperextensible joints

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7
Q

PG are highly charged therefore attract water and form a hydrated gel. what does this do

A

provides resistance to compression

results in swelling pressure (turgor)

provides strength and support

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8
Q

what are the features of chondrocyte

A

only 5-10% of ECM volume

large and mature,

in groups of 2-8 cells

rich in RER and Golgi

secrete high amounts of type II collagen and aggrecan

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9
Q

in which ECM are chondrocytes found

A

avascular (hypoxic)

alymphatic

aneuronal

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10
Q

when do Chondrocytes differentiate

A

during embryonic development

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11
Q

what cells do Chondrocytes differentiate from

A

mesenchymal stem cells MSC

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12
Q

cells that make cartilage can change their matrix to make bones

A

TRUE

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13
Q

what are the features of MSC that differentiate into chondrocytes

A

expression of Sox-9 (HMG-box DNA binding
transcription factor) leads to Col2A expression

chondrocyte proliferation and ECM synthesis
requires:
- TGF-b, fibroblast growth factor (FGF),

  • insulin-like growth factor (IGF-1)
  • parathyroid hormone-related protein
    (PTHrP)

As a result of “spatial” chondrocyte proliferation and ECM synthesis, the “cartilage model” forms during embryonic development

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14
Q

what is ossification

A

bone formation

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15
Q

what is Intramembranous/Endochondrial Ossification

A

“cartilage model” is replaced by bone during fetal development. e.g. long bones

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16
Q

what initiates Endochondrial Ossification

A

differentiation of MSC into osteoblasts, chondrocytes die and cavities (lacunae) form

17
Q

what cells are present in bones

A

osteoblasts

18
Q

what are morphogens

A

secreted signaling molecules that orchestrate Spatial patterning (location) of chondrocytes
during bone formation

19
Q

how does Spatial patterning (location) of chondrocytes happen during bone formation

A

via inductive signaling

20
Q

what does inductive signaling mean

A

cells away from other cells become different in a spatial way

21
Q

what does inductive signaling require

A

morphogens passing between cells through the developing ECM

22
Q

what members of the Hedgehog family of proteins are involved in inductive signaling

A

Sonic (SHH), Desert (DHH), Indian IHH)

23
Q

what does inducive signaling control

A

the production of the key skeletal morphogen PTHrP.

24
Q

how do IHH and PTHrP interact

A

positive feedback loops that maintain spatial chondrocyte proliferation

25
Q

what does hedgehog interact with in drosophila, and what does this result in

A

with Patched and Smoothened,

keeps proteolytic processing of Cubitus interruptus (Ci) turned off, so it can move to nucleus and activate gene expression

26
Q

what is Ci in vertebrates

A

GL11-13

27
Q

what does hedgehog do

A

activates smoothened

repressor is cleaved

leading to transcription of hedgehog target genes

28
Q

what happens when PTHrP binds to a G-protein coupled receptor (GPCR)

A

+ve feedback

29
Q

what does osteoid ECM contain

A

hydroxyapatite and collagen

30
Q

what happens to osteoid ECM when cartilage is catabolized

A

it becomes calcified, trapping osteoblasts

31
Q

How does the morphogen IHH induce hyaline cartilage polarization within the long bones

A

it regulates Chondrocyte Proliferation and Hypertrophy

IHH induces the expression of PTHrP in the resting zone.

PTHrP acts on proliferative and prehypertrophic chondrocytes to delay their hypertrophic differentiation.

This creates a negative feedback loop:

  • IHH promotes PTHrP production.
  • PTHrP inhibits hypertrophic differentiation, maintaining a balance between proliferation and maturation.

This feedback ensures the proper spatial arrangement and polarization of chondrocytes within the growth plate.

BMS2002 (14 decks)

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