[2] Lecture 13 Osteogenesis and Joints

Question 1

Osteoblasts secrete osteoid, trapping some of the osteoblasts

Answer 1

Blastema

Question 2

Aggregation of mesenchymal cells is controlled by:

Answer 2

Wnt, Hedghog, FGF, TGF-Beta

Question 3

How do Osteoblast form osteocytes?

Answer 3

They’re trapped osteoblasts

Question 4

Steps intramembranous bone formation:

Answer 4

1. Aggregation of mesenchymal cells
2. Mesenchymal cells-> osteoblasts
3. Osteoblasts secrete osteoid, trapping some of the osteoblasts [blastema]
4. Trapped osteoblasts->osteocytes
5. mineralization occurs via Ca++ ions
6. Osteoblasts form epithelial like covering over 1˚ bone tissue, can secrete more osteoid on surface.
7. 1˚ossification center becomes trabecula.
8. Numerous trabeculae fuse together to form spongy bone

Question 5

Initial bone=

Answer 5

Woven bone;

Collagen fibers are arranged randomly.

Question 6

What type of bone occurs when collagen fibers become aligned?

Answer 6

Lamellar bone

Question 7

Lamellar bone changes:

Answer 7

Becomes symmetrically arranged concentric ally forming Haversian canals

Question 8

Usually consists of 2 layers of compact bone enclosing a layer of spongy bone [diploe]

Answer 8

Membrane bone

Question 9

Cartilage is replaced by bone

Answer 9

Endochondral bone formation

Question 10

Steps of endochondral bone formation:

Answer 10

1. 1˚ ossification center occurs in future diaphysis of cartilage model.
2. Chondrocytes become hypertrophic.
3. chondrocytes secrete vascular endothelial growth factor.
4. BLood vessels break through perichondrium, bringing in osteoprogenitor cells.
5. Hypertrophic cartilage cells undergo apoptosis, leaving behind thin strands of calcified matrix.
6. osteoblasts use calcified strands as substrates for deposition of osteoid.
7. osteoid is calcified.

Question 11

Primary ossification:

Answer 11

Diaphysis

Question 12

Secondary ossification:

Answer 12

Epiphyses

Question 13

4 zones of endochondral bone formation:

Answer 13

Reserve zone
Proliferation zone
Hypertrophic zone
Vascular invasion zone

Question 14

Break down bone in center of diaphysis, forming medullary cavity

Answer 14

Osteoclasts

Question 15

Cartilage is replaced by bone at which side of the epiphyseal plate?

Answer 15

Proximal

Question 16

Cartilage is continually added to _____ end of epiphyseal plate

Answer 16

Distal

Question 17

Is articular cartilage covered by periosteum?

Answer 17

NO

Question 18

When epiphysis fuses w. Diaphysis:

Answer 18

Growth stops

Question 19

Proliferation is stimulated by:

Which also prevents hypertrophy

Answer 19

Indian hedgehog [ihh]

Question 20

Form calcified matrix
Synthesize type X collagen,
Secrete vascular endothelial GF,
Signal perichondrial cells to become osteoblasts

Answer 20

Hypertrophic Chondrocytes

Question 21

4 steps of bone remodeling:

Answer 21

Activation
Resorption
Reversal
Formation

Question 22

Osteoblast recruited to become osteoclasts;
Osteoclasts lining the inner lamella begin resorption process.

Which stage of bone remodeling?

Answer 22

Activation

Question 23

Additional osteoclast recruited and resorption slightly past boundary of osteon;
when Osteoclasts stop removing bone, osteoblasts appear

Which stage of bone remodeling?

Answer 23

Resorption

Question 24

Osteoblasts reverse resorption process by organizing a layer inside reabsorption cavity-secretes osteoid.

Which stage of bone remodeling?

Answer 24

Reversal

Question 25

Osteoblast continue laying down bone and eventually become trapped within the mineralized bone Which stage of bone remodeling?

Answer 25

Formation

Question 26

Where 2 bones come together:

Answer 26

Joint

Question 27

Cartilaginous joints:

Answer 27

Amphiarthroses

Question 28

Amphiarthroses types of joints and their cartilage type:

Answer 28

Symphysis: fibrocartilage Synchondrosis: hyaline cartilage

Question 29

Ex of symphysis joints

Answer 29

Intervertebral discs and pubic symphysis

Question 30

Ex synchondrosis joints:

Answer 30

Epiphyseal plates and 1st sternocostal joint

Question 31

Fibrous joints: and their joining material

Answer 31

Synarthroses: collage nous or elastic fibrous CT

Question 32

3 types of fibrous: synarthroses

Answer 32

Suture Gomphosis Syndesmosis

Question 33

Ex of suture

Answer 33

Joints between bones of the Calvaria

Question 34

Ex of gomphosis

Answer 34

PEg in the socket= | Tooth in alveoli

Question 35

Ex of Syndesmosis:

Answer 35

Fused by fibrous membrane such as the fibrous membrane between tibia and fibula.

Question 36

Synovial joints: what're they?

Answer 36

Diarthroses Movable joints exemplified by Connective capsule surrounding fluid-filled joint space. Synovial joints reinforced outer capsule by ligaments.

Question 37

How are types of synovial joints classified?

Answer 37

Based on degree of freedom of movement.

Question 38

Joints allowing movement in one plane only: types:

Answer 38

Monoaxial: Hinge And Pivot

Question 39

Ex of hinge joint

Answer 39

Humeroulnar and knee joints

Question 40

Ex pivot joint

Answer 40

Atlantoaxial And Radioulnar joints

Question 41

Joints allowing movement in two planes: types:

Answer 41

Biaxial Condyloid And Saddle

Question 42

Ex of condyle is joint:

Answer 42

Metacarpophalangeal and atlantooccipital

Question 43

Ex of a saddle joint:

Answer 43

First carpometacarpal joint

Question 44

Joints allowing movement in three planes: types:

Answer 44

Triaxial Ball and socket joints:

Question 45

Ex of ball and socket joints:

Answer 45

Glenohumeral and femoroacetabular joints

Question 46

Articular cartilage is made up of:

Answer 46

Hyaline cartilage- slippery

Question 47

Synovial joint is made up of:

Answer 47

- Cavity - Capsule: outer fibrous (innervated)and inner synovial[vascularized] - Ligaments: Thickening of fibrous capsule attached by sharpey's fibers - Synovial fluid: dialysate located in the synovial cavity - articular cartilage

Question 48

Hyaline cartilage Lacks perichondrium Not lined by synovial membrane

Answer 48

Articular cartilage

Question 49

Vascularized dense CT Lined by synovial membrane Attached to edges of articular cartilage

Answer 49

Joint capsule

Question 50

Highly vascularized -fenestrated capillaries 1-3 layers of synovial cells No basal lamina

Answer 50

Synovial membrane

Question 51

Leaky...has holes in membranes

Answer 51

Fenestrated capillaries

Question 52

Contains mucin [hyaluronic acid-protein complex] | Produced by synovial cells

Answer 52

Synovial fluid

Question 53

Synovial cells:

Answer 53

Type A=macrophage-like | Type B=Fibroblast-like