Cartilage and bone

Question 1

Perichondrium consists of

Answer 1

proteoglycans and type 1 and 3 collagen

Question 2

Cartilage matrix consists of

Answer 2

type 2 collagen and proteoglycans

Question 3

Hyaline cartilage is mainly composed of

Answer 3

Type 2 collagen and aggrecan

Question 4

Most abundant collagen type

Answer 4

2

9,11,6 also prevalent

Question 5

ECM consists of

Answer 5

collagen and proteoglycans

Question 6

Articular cartilage has no

Answer 6

perichondrium , but a periosteum

Question 7

MMP does what

Answer 7

breaks down aggregan and proteins

Question 8

Fibrocartilage contains what type of collagen

Answer 8

Type 1

Question 9

Bone matrix contains which type of collagen

Answer 9

Type 1

Question 10

osteoblasts and osteocytes are of which lineage

Answer 10

Mesenchymal

Question 11

Osteoclasts are of which lineage

Answer 11

Monocytic/macrophage

Question 12

Matrix vesicles contain

Answer 12

enzymes that help nucleate the hydroxyapatite to form crystals

Question 13

Molecules of osteoclasts that help break down bone

Answer 13

cathepsin-K and matrix metalloproteins

Question 14

Describe regulation of osteoblasts and osteoclasts

Answer 14

1. Osteoblasts secrete M-CSF, which binds to a receptor on monocytes causing them to turn into macrophages.
2. Macrophages express RANK receptor on the surface
3. Osteoblasts synthesize RANK-L which binds to RANK-R on the macrophages and causes the macrophages to turn into osteoclast precursors, then resting osteoclast and then functional osteoclasts.
4. Osteoblasts also secrete osteoprotegerin (OPG) . OPG also binds to RANK -L with greater affinity than RANK-R. The binding of OPG to RANK-L prevents the osteoclasts precursors from becoming functional osteoclasts. Osteoprotegrin is a natural inhibitor of osteoclast formation and could be used to prevent osteoporosis.

Question 15

Lateral mesoderm

Answer 15

appendicular skeleton

Question 16

Intramembranous ossification

Answer 16

mesenchyme condenses and forms bone blastema which then differentiates into osteoblasts and lays down bone layers (appositional growth ) then the osteoblast become osteocytes

Question 17

Endochondrial ossification

Answer 17

Starts out as undifferentiated mesenchymal cells .. these cell proliferate and diff into chondrocytes rather than osteoblasts. Then perichondrium then forms and becomes vascularized and it will secrete regulatory factors.

The chondrocytes hypertrophy. Then they die once they 1. mineralize the matrix, and 2. secrete factors that will cause vasculature to come into the bone.

Then the osteoprogenitor cells come in either from the perichondrium or from the vasculature and lay down bone matrix to remodel cartilage to bone. This starts in the center which is the primary ossification center. Growth plate eventually closes.

Question 18

FGFR3 mutation

Answer 18

results in inactivation (AD) Achondroplasia . Chondrocytes don’t divide.

Question 19

Activating mutation in PTH/PTHrP

Answer 19

Jansen type metaphyseal chondroplasia

-cartilage doesn’t turn to bone

Question 20

Inactivating mutation ofPTH/PTHrP

Answer 20

Blomstrand lethal chondroplasia

-accelerating hypertrophic diff , as soon as cartilage is formed, it turns to bone.

Question 21

Local growth factors

Answer 21

FGF and PTH/PTHrP

Question 22

GH regulates

Answer 22

expression of insulin like GFs (insulin like GF can act locally or systemically).

Question 23

If fracture is big enough, it will go through which repair mechanism

Answer 23

Mesenchymal cells will go directly into bone.