MSK 02 - Bone-I

Question 1

Discuss the basic composition of bone ECM

Answer 1

Question 2

What do osteoblasts do? What cells do they arise from?

Answer 2

Osteoblasts secrete the osteoid (the organic unmineralized bone ECM) and they arise from the osteoprogenitor (osteogenic) cells.

Question 3

Describe some visually distinguishing characteristics of osteoblasts.

Answer 3

They are basophilic

May appear as a cuboidal layer (if highly active) or flattened (if less active)

Cytoplasmic processes contact them with other osteoblasts or osteocytes

They possess PAS positive granules that are most likely the precursors of the glycosaminoglycans of the osteoid matrix

Question 4

What is bone lacuna? What is a bone canaliculus?

Answer 4

Bone Lacuna - a small space containing an osteocyte in bone

Bone Canaliculus - microscopic canals between the lacunae of ossified bone.

Question 5

What are osteocytes? What do they do? What are some of their distinguishing characteristics?

Answer 5

Osteoblasts that become entrapped in their own matrix (lacunae).

They help to maintain bone tissue by maintaining communication, and exchanging nutrients and metabolites via gap junctions between their narrow cytoplasmic processes extending through the canaliculi

They have increased amounts of condensed nuclear chromatin, reduced amounts of RER and a smaller Golgi vs osteoblasts

Question 6

Answer 6

Question 7

How are osteoclasts formed and where are they found?

Answer 7

Question 8

How are Howship’s lacunae formed?

Answer 8

By the osteolytic activity of osteoclasts

Question 9

Discuss the three distinct regions of the osteoclasts.

Answer 9

Question 10

Answer 10

Question 11

Discuss the process of bone resorption.

Answer 11

Question 12

What are osteogenic cells? Where are they found? What do they do? What do they arise from?

Answer 12

Question 13

What are bone lining cells? Where are they found? What is their function?

Answer 13

Question 14

Answer 14

Question 15

What are the periosteum and endosteum?

Answer 15

They are non-calcified connective tissue layers that cover the external (periosteum) and internal (endosteum) surfaces of the bone, except over articular surfaces.

Question 16

Discuss the composition of the periosteum and endosteum.

Answer 16

Question 17

Facts to know about bone growth

Answer 17

Question 18

What is immature bone? What are some other names for immature bone?

Answer 18

Question 19

What is mature bone? What are some other names for mature bone?

Answer 19

Question 20

Answer 20

Immature bone

Question 21

Answer 21

Mature bone

Question 22

What are the two types of mature bone? Briefly describe them.

Answer 22

Question 23

Answer 23

Question 24

What is the functional unit of compact bone?

Answer 24

The Haversian system or Osteon which is 4 to 20 concentric layers of compact bone tissue (aka lamellae) in a cylindrical shape with numerous canaliculi to permit communication and a central Haversian canal that carries blood vessels and nerves.

Question 25

Are the Haversian systems in parallel? Why or why not?

Answer 25

Question 26

What does each lamella of compact bone consist of?

Answer 26

Multiple parallel arrays of collagen fibers. Adjacent lamellae have alternating directions of collagen fibers providing great strength despite its light weight.

Question 27

Facts to know about the circumferential lamellae.

Answer 27

Question 28

What are Volkmann’s canals? What is their purpose?

Answer 28

Question 29

Answer 29

Question 30

Answer 30

1. Osteon
2. Haversian Canal
3. Volkmann’s Canal
4. Circumferential Lamellae
5. Insterstitial Lamellae
6. Osteocytes
7. Endosteum
8. Canaliculi