Bone Development

Question 1

Intramembranous Ossification

Answer 1

• Direct
• Mesenchymal Condensation and direct mineralization by osteoblasts
• differentiation of mesenchymal cells into osteoblasts then osteocytes

Question 2

Endochondral Ossifiation

Answer 2

• Indirect
• Ossification of a preexisting cartilage model
• replacement of cartilage with osteoblasts and osteocytes

Question 3

Intramembranous Ossification occurs in…..

Answer 3

• areas of vascularized mesenchyme
• flat bones
• growing short bones
• periosteal bone collar of long bones

Question 4

Intramembranous ossification sequence of events:

Answer 4

1) mesenchymal condensations
2) appearance of blood vessels
3) differentiation into osteoblasts: primary ossification center
4) mineralizaiton by osteocytes
5) spicules/ trabeculae formed
6) interweaving of trabeculae: spongy bone and marrow cavities

Question 5

Endochondral Ossification in Prenatal growth

Answer 5

• Formation of subperiosteal bone collar by intramembranous ossification around hyaline cartilage (width)
• Endochondral ossification- replaces the cartilage with bone (length)

Question 6

Endochondral Ossification in postnatal growth

Answer 6

• Formation of a secondary epiphyseal ossification center in one of the epiphysis following the same mechanism as for primary center
• Epiphyseal growth plate- bone growth in length until adulthood, regulated by GH
• Spongy bone replaces woven bone at the first epiphysis. Articular cartilage remains around the epiphyisis

Question 7

Growth Plate Closure

Answer 7

• The first epiphysis matures: growth plate closes and progressively disappears (16-20y.)
• Only remaining cartilage in the epiphysis is articular cartilage
• growth of second epiphyseal plate
• expansion of central marrow cavity
• bone collar becomes compact bone

Question 8

Adult bone

Answer 8

• Plate no longer present
• compact bone at diaphysis
• spongy bone at epipysis
• Marrow space contains yellow marrow
• periosteum surrounds shaft
• articular cartilage without perichondrium

Question 9

Epiphyseal spicules

Answer 9

• get incorporated into diaphysis

Question 10

Mitotic zone (proliferating zone)

Answer 10

• GH is causing proliferation of chondroblasts
• pushes up height of long bone
• the thickness on the trailing end is converted to bone
• ratchets up

Question 11

Bone Repair

Answer 11

• Blood supply is broken
• Oxygen supply decreases
• Mesenchymal cells go toward cartilage because there is no blood supply
• chondrocytes are formed
• forms a temporary bridge between the two broken bones- 4 days
• Blood vessels re penetrate the cartilage
• they you get cartilage replacement- endochondral

Question 12

Joints

Answer 12

• arthroses

- Synarthrose- permit little or no movement

Question 13

syndesmosis

Answer 13

• Fibrous joints

- Joined by dense connective tissue

Question 14

synostose

Answer 14

• immobilized fused bones (skull)

Question 15

Synchondrose

Answer 15

• bones joined by hayline cartilage
  (rib/sternum)
• primary carilaginous joint

Question 16

Symphysis

Answer 16

• secondary cartilaginous joint

- bones joined by fibrocartilage (pubic symphysis, intervertebral discs)

Question 17

Diarthrose

Answer 17

• synovial/ articular joint
• movable joints between long bones
• Articular cartilage (no perichondrium
• Synovial Fluid
• Capsule (2 layers)
  1) Outer membrane: fibrous
  2) inner membrane: synovial membrane
• A cell: Phagocytic, adjacent to synovial fluid
• B cel: secretes synovial fluid

Question 18

Tendon

Answer 18

• muscle to bone

Question 19

Ligament

Answer 19

Bone to bone

Question 20

Rheumatoid Arthritis

Answer 20

Autoimmune disease causing chronic inflammation of the joint and can also cause inflammation of the tissue around the joints