Histology: Connective Tissue- Bone

Question 1

What are bones? What do they consist of?

Answer 1

• speacialized forms of connective tissue
• consisting of cells and the ECM

Question 2

What is a feature that distinguished bones from other connective tissues?

Answer 2

the mineralization of its matrix

Question 3

What does the mineralization of the bone matrix produce?

Answer 3

an extremely hard tissue capable of providing support and protection

Question 4

Why are there so many similarities between bones and cartilage?

Answer 4

bones are derived/developed from hyaline cartilage

Question 5

Why can newborns not walk right after birth?

Answer 5

the bones are not fully developed yet. Bones are under the process of exchanging from hyaline cartilage to bones.

Question 6

Explain the general structure of the bone tissue.

Answer 6

• bone matrix spaces = lacunae
• each lacunae contains an osteocyte
• each osteocyte extends numerous processes into small tunnels called canaliculi

Question 7

What allows for contact between the cell processes of neighbouring osteocytes?

Answer 7

canaliculi course through the mineralized matrix connecting adjacent lacunae.

Question 8

What happens instead of diffusion processess in bones?

Answer 8

canaliculi systems connect the osteocytes together.

Question 9

What is mature (lamellar) bone composed of?

Answer 9

osteons (haversian systems)

Question 10

What are the concentrix lamellar structures organised around?

Answer 10

osteonal (Haversian) canal

Question 11

What does the osteonal (Haversian) canal contain?

Answer 11

• vascular sypply of the osteon
• nerve supply of the osteon

haver- nerves and blood

Question 12

What canals are perpendicularily arranged and connected to osteonal canals?

Answer 12

Perforating (Volkmann’s) canals

connects haversian canals

Question 13

What do the lacunae contain?

Answer 13

osteocytes

Question 14

How are osteocytes interconnected?

Answer 14

canaliculi

Question 15

What are the spaces between osteons which can be visualized in the real microscopic picture?

Answer 15

creation/reorganisation/destruction of osteons

Question 16

What do bones do to ensure that they are always strong and protected from environmental factors?

Answer 16

Their osteons are consinuously reorganised, destroyed and created.

Question 17

Why do older people have a higher risk of bone fracturing?

Answer 17

the capasity of reorganisation of osteons decreases with age.

Question 18

What are the 4 cells of bones?

Answer 18

1) osteocytes
2) osteoblasts
3) osteogenic cells (osteoproginators)
4) osteoclasts

Question 19

What are osteoproginators? What is another name for them?

Answer 19

• cells derived from mesenchymal stem cells,
• they give rise to osteoblasts.
• also called OSTEOGENIC CELLS

Question 20

What are osteoblasts?

Answer 20

• cells which secrete extracellular matrix of the bone

Question 21

What are osteocytes?

Answer 21

• osteoblasts which do not secrete the ECM anymore
• cells which are surrounded by the secreted extracellular matrix

Question 22

What are bone lining cells?

Answer 22

• cells that remain on the bone surface when there is no active growth
• derived from osteoblasts that remain after bone deposition ceases

Question 23

What are osteoclasts?

Answer 23

• bone-resorbing cells present on bone surfaces where bone is being removed, remodeled, or has been damaged.
• macrophages

Question 24

What is the main difference between the osteoblast and the osteocyte?

Answer 24

The osteoblast is very actively producing ECM.
Once enough ECM is produced, (and the cell reaches the desired size), the production of ECM is stopped (still producing just in very small amounts and not very actively) –> osteoblast becomes osteocyte.

BLAST–> produces extracellular MATRIX

Question 25

What types of bone cells make up the canaliculi system?

Answer 25

osteoclasts and osteocytes

osteoCLasts- CanaLiculi systems