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Musculoskeletal System > 10. Cartilage and Bone Growth > Flashcards

10. Cartilage and Bone Growth Flashcards

1
Q

what is ENDOCHONDRAL OSSIFICATION

A

when BONE REPLACES existing CARTILAGE

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2
Q

what is INTRAMEMBRANOUS OSSIFICATION

A

when BONE develops directly from MESENCHYME or FIBROUS CONNECTIVE TISSUE

(skull, clavicle)

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3
Q

HYALINE CARTILAGE has 2 MAIN ROLES in BONE (2 forms):

A
  • GROWTH PLATE CARTILAGE
  • ARTICULAR CARTILAGE
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4
Q

is GROWTH PLATE CARTILAGE stable or transient

A

TRANSIENT
- destined to be REPLACED BY BONE

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5
Q

is ARTICULAR CARTILAGE stable or transient

A

STABLE

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6
Q

6 STEPS of FORMATION of ARTICULATION (joint)

A
  1. MESENCHYMAL CELLS CONDENSE
  2. Joint Site Determination
    • INTERZONE is formed : where mesenchymal cells GATHER
      - mesenchymal cells then DIFFERENTIATE into CHONDROCYTES
  4. Chondrocytes secrete CYTOKINE GDF5 which INDUCES CAVITATION (formation of an EMPTY SPACE within a solid object)
  5. Morphogenesis (shaping)
  6. JOINT FORMATION
    may become SYNOVIAL JOINT eg knee joint
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7
Q

which CYTOKINE INDUCES CAVITATION during formation of ARTICULATION

A

GDF5

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8
Q

GDF5 expressing cells (joint progenitors) undergo different SIGNALLING PATHWAYS to form different parts.

what signalling will form SYNOVIAL LINING & LIGAMENTS:

A
  1. ANTI-CHONDROGENIC SIGNALLING
  2. Wnt signalling (some)

form SYNOVIAL LINING & LIGAMENTS

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9
Q

GDF5 expressing cells (joint progenitors) undergo different SIGNALLING PATHWAYS to form different parts.

what signalling will form ARTICULAR CARTILAGE at the END of bone

A
  1. ANTI-CHONDROGENIC SIGNALLING
  2. NOTCH signalling (some)

form ARTICULAR CARTILAGE

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10
Q

GDF5 expressing cells (joint progenitors) undergo different SIGNALLING PATHWAYS to form different parts.

what signalling will form GROWTH PLATE cartilage

A

GDF under the regulation of SOXs
CHONDROGENIC

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11
Q

GDF5 expressing cells (joint progenitors) undergo different SIGNALLING PATHWAYS to form different parts.

cells that undergo ANTI-CHONDROGENIC signalling can take two pathways.
some take…to form…
some take… to form…

A

either
- WNT SIGNALLING to form SYNOIVAL LINING & LIGAMENTS
or
- NOTCH SIGNALLING to form ARTICULAR CARTILAGE

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12
Q

GDF5 expressing cells (joint progenitors) undergo different SIGNALLING PATHWAYS to form different parts.

is CHONDROGENIC pathway to form GROWTH PLATE, what Transcription Factor is requires

A

SOXs

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13
Q

steps of ENDOCHONDRAL OSSIFICATION

A
  1. MESENCHYMAL CELLS CONDENSE
  2. DIFFERENTIATE into CHONDROCYTES
  3. some chondrocytes DIFFERENTIATE into HYPERTROPHIC CHONDROCYTES
  4. PERICHONDRIAL CELLS DIFFERENTIATE into OSTEOBLASTS, forming BONE COLLAR.
    HYPERTROPHIC CHONDROCYTES undergo APOPTOSIS and BLOOD VESSEL COMES IN (vascular invasion)
  5. OSTEOBLASTS and BLOOD SUPPY allow primary bone formation - PRIMARY SPONGIOSA FORMED
  6. chondrocytes continue to PROLIFERATE, lengthening the bone
  7. (postpartum) SECONDARY OSSIFICATION CENTRE
    forms through INVASION of BLOOD SUPPLY (vascular invasion) into head of bone
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14
Q

in the growth plate PROLIFERATING CHONDROCYTES form…

A

COLUMNS

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15
Q

COLUMN FORMATION of CHONDROCYTES in the GROWTH PLATE is driven by which CHEMOKINE
and how

A

IHH - INDIAN HEDGEHOG

  • stimulates column formation through ACTIVATION of PARATHYROID HORMONE RELATED PROTEIN
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16
Q

when CHONDROCYTES become HYPERTROPHIC CHONDROCYTES they change MATRIX formation and SWITCH from COLLAGEN TYPE II to …

A

COLLAGEN TYPE 10 (X)

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17
Q

What happens after HYPERTROPHIC CHONDORCYTES under APOPTOSIS

A

OSTEOBLASTS COME IN and form PRIMARY SPONGIOSA

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18
Q

What are SECRETED in HYPERTROPHIC CHONDROCYTES
and what do they do

A

METALLOPROTEASES

  • REMODEL CARTILAGE so bone can INVADE
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19
Q

what happens to the GROWTH PLATE in ADULT BONE

A

ENDS / CLOSES
(bone formation there instead)

20
Q

BONE GROWTH occurs through the..

A

GROWTH PLATE CARTILAGE

21
Q

4 STAGES of CHONDROCYTES

A
  • PROLIFERATING chondrocyte
  • PREHYPERTROPHIC chondrocyte
  • HYPERTROPHIC chondrocyte
  • TERMINAL chondrocyte
    (apoptose)
22
Q

CHONDROCYTES and their different stages are REGUALTED by..

A

TRANSCRIPTION FACTORS

(SOX9
Pthrp -> IHH
SOX5/6
RUNX2/3
MEF2C/D
Wnt/Beta-Catenin)

23
Q

name of one of the TRANSCRIPTION FACTORs that REGULATE a PROLIFERATING CHONDROCYTE

A

SOX9

also SOX5/6

and chemokine IHH

24
Q

for PREHYPERTROPHIC and HYPERTROPHIC CHONDROCYTES which TRANSCRIPTION FACTOR is SWITCHED ON

A

RUNX2/3

(REPLACES SOXs - switched off)

25
Q

what is DIFFERENT about INTRAMEMBRANOUS OSSIFICATION as opposed to Endochondral

A

MESENCHYMAL CELLS condense and become OSTEOBLASTS
- WITHOUT CHONDROCYTE FORMATION

NO CARTILAGE INTERMEDIARY

26
Q

TRANSCRIPTION FACTORS used in INTRAMEMBRANOUS OSSIFICATION

A

no SOXs

skeletogenic cell -> immature osteoblast
RUNXS
OSX
(IHH)

immature osteoblast -> mature osteoblast
ATF4

27
Q

INTRAMEMBRANOUS OSSIFICATION is dependent on..

A

MESENCHYMAL CONDENSATION

28
Q

IHH increases the length of proliferative columns by:
directly..
indirectly..

A

Directly acting at the top of these columns present in the growth
plate

Indirectly through the actions of PTHrP (parathyroid hormone related protein)

29
Q

which HORMONES are IMPORTANT in BONE GROWTH

  • CORRECT LEVELS of these hormones are important
A

GROWTH HORMONE,
GLUCOCORTICOIDS eg cortisol,
THYROID HORMONE,
SEX HORMONES

30
Q

why is PARATHYROID HORMONE important in BONE GROWTH

A

CALCIUM-REGULATING

MAINTAINS the levels of CALCIUM (INCREASES)
- STIMULATES both RESORPTION and FORMATION of BONES

31
Q

why is CALCITRIOL an important hormone in BONE GROWTH

A

DERIVED FROM VITAMIN D (activated by PTH)

STIMULATES INTESTINES to ABSORB CALCIUM
- INCREASES CALCIUM

32
Q

why are SEX HORMONES important in BONE GROWTH

A

STRENGTH

LOW ESTROGEN/TESTOSTERONE leads to WEAKER BONES

33
Q

why is ARTICULAR CARTILAGE IMPORTANT

A

SPREAD the LOAD

& REDUCE FRICTION
friction free movement

34
Q

why is LOAD important

A

MAINTAINS (ARTICULAR) CARTILAGE

long periods of time without load (eg in bed) can cause degradation of articular cartilage

35
Q

BONE and CARTILAGE are designed to … and … MECHANICAL LOADING

A

RESIST mechanical loading
& ADAPT TO mechanical loading

36
Q

CARTILAGE GROWS by 2 means:

A
  • INTERSTITIAL
  • APPOSITIONAL
37
Q

what is INTERSTITIAL GROWTH

A

GROWTH FROM WITHIN

  • In EPIPHYSEAL GROWTH PLATE

chondrocytes divide, cartilage enlarges

38
Q

what is APOSITIONAL GROWTH

A

NEW LAYERS of CARTILAGE being ADDED to the surface

  • via PERICHONDRIUM
  • BONE INCREASES SIZE
39
Q

which type of CARTILAGE GROWTH occurs in the EPIPHYSEAL GROWTH PLATE

A

INTERSTITIAL

40
Q

BONE can only INCREASE IN SIZE by which type of growth

A

APPOSITION

bone does NOT increase in size by interstitial growth

41
Q

why do we need CHONDROCYTES in ENDOCHONDRAL OSSIFICATION

A

OSTEOBLASTIC APPOSITION is NOT SUFFICIENT to SUSTAIN RAPID LONGITUDINAL GROWTH

42
Q

the Capacity for LONGITUDINAL GROWTH is MAINTAINED by the PERSISTENCE of..

A

EPIPHYSEAL GROWTH CARTILAGES

43
Q

CARTILAGE undergoes…
(which growth)

A

INTERSTITIAL GROWTH and is REPLACED BONE

44
Q

CHILDHOOD and ADOLESCENCE BONES are SCULPTED by a process called..

A

MODELLING

which allows for the formation of new bone at one site and the removal of old bone from another site within the SAME bone

45
Q

what happens to HYPERTROPHIC CHONDROCYTES in ENDOCHONDRAL OSSIFICATION

A

DIE (APOPTOSIS) in the calcified matrix surrounding them

Musculoskeletal System (18 decks)

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