Lecture 11

Question 1

List the steps involved in the formation of intramembranous bone.

Answer 1

1. Mesenchymal cells aggregate.
2. Mesenchymal cells differentiate into osteoblasts
3. The osteoblasts secrete osteoid, the osteoid traps some of the osteoblasts forming a blastema
4. The trapped osteoblasts turn into osteocytes and form a functional syncytium
5. Osteoblasts secretes more osteoid
6. Calcium is used in the mineralization process and bone tissue is formed

Question 2

List the steps of endochondral bone formation.

Answer 2

1. Chondrocytes enlarge
2. Endothelial growth factor is secreted by chondrocytes, this attracts blood vessels
3. The blood vessels break through the perichondrium and brings in osteoprogenitors
4. The cartilage DIES, leaving behind thin strands of calcified matrix
5. Osteoblasts use the strands for deposition of osteoid
6. Osteoid is calcified!

Question 3

What are the zones of the epiphyseal plate? What are the characteristics of the zones?

Answer 3

Proliferative Zone - chondrocytes align
Hypertrophic Zone - apoptosis of chondrocytes, attract blood vessels by EGF secretion, and calcification of the territorial matrix
Vascular Invasion Zone - blood vessels penetrate, carrying osteoprogenitor cells with them

Question 4

What is the osteoclastic chase and chondrocytic run mechanism?

Answer 4

I am not really sure TBH but this is a guess:

Chondrocytes are replaced and proliferate causing an increase in the length of the cartilage

Question 5

What are the four steps in bone remodeling?

Answer 5

1. Activiation - Osteoclast precursors are recruited to the haversian canal and differentiate into osteoclasts
2. Resorption - Osteoclasts stop removing bone, osteoblasts appear
3. Reversal - Osteoblasts reverse the process by secreting osteoid inside the reabsorption cavity. New bone lamellae continues to be deposited towards the center of the osteon.
4. Formation - Osteoblasts continue to lay down bone until they become trapped and become osteocytes. A new osteon is formed leaving interstitial lamellae

Question 6

What is the relationship between osteoclasts and osteoblasts in the bone remodeling process?

Answer 6

Osteoclasts and osteoblasts seem to swap back and forth and become each other and one leads to the other and all that shit

Question 7

Define “joint”

Answer 7

Where two bones come together

Question 8

What is the major characteristic used to classify joints?

Answer 8

The connective tissue that is used to join bones together

Question 9

What are the major categories and sub-categories of joints?

Answer 9

1. Cartilaginous
   a. Symphysis (fibrocartilage)
   b. Synchondrosis (hyaline cartilage)
2. Fibrous
   a. suture
   b. gomphosis
   c. syndesmosis
3. Synovial
   a. Monaxial
   b. Biaxial
   c. Triaxial

Question 10

Give examples of each of the sub-categories of joints.

Answer 10

Symphysis - intervertebral discs
Synchondrosis - epiphyseal plates, first sternocostal joint
Suture - between bones of calvaria
Gomphosis - Teeth in the alveoli
Syndesmosis - fibrous membrane between the tibia and fibula
Monaxial - (hinge, pivot) knee, radioulnar
Biaxial - (condyloid, saddle joint) metacarpophalangeal, thumb stuff
Triaxial - (ball and socket) shoulder, hip

Question 11

Describe the histology of a synovial joint.

Answer 11

• Articular cartilage
• joint capsule
• synovial membrane
• synovial fluid
• synovial cells