Histology: Connective Tissue- Bone Flashcards
What are bones? What do they consist of?
- speacialized forms of connective tissue
- consisting of cells and the ECM
What is a feature that distinguished bones from other connective tissues?
the mineralization of its matrix
What does the mineralization of the bone matrix produce?
an extremely hard tissue capable of providing support and protection
Why are there so many similarities between bones and cartilage?
bones are derived/developed from hyaline cartilage
Why can newborns not walk right after birth?
the bones are not fully developed yet. Bones are under the process of exchanging from hyaline cartilage to bones.
Explain the general structure of the bone tissue.
- bone matrix spaces = lacunae
- each lacunae contains an osteocyte
- each osteocyte extends numerous processes into small tunnels called canaliculi
What allows for contact between the cell processes of neighbouring osteocytes?
canaliculi course through the mineralized matrix connecting adjacent lacunae.
What happens instead of diffusion processess in bones?
canaliculi systems connect the osteocytes together.
What is mature (lamellar) bone composed of?
osteons (haversian systems)
What are the concentrix lamellar structures organised around?
osteonal (Haversian) canal
What does the osteonal (Haversian) canal contain?
- vascular sypply of the osteon
- nerve supply of the osteon
haver- nerves and blood
What canals are perpendicularily arranged and connected to osteonal canals?
Perforating (Volkmann’s) canals
connects haversian canals
What do the lacunae contain?
osteocytes
How are osteocytes interconnected?
canaliculi
What are the spaces between osteons which can be visualized in the real microscopic picture?
creation/reorganisation/destruction of osteons
What do bones do to ensure that they are always strong and protected from environmental factors?
Their osteons are consinuously reorganised, destroyed and created.
Why do older people have a higher risk of bone fracturing?
the capasity of reorganisation of osteons decreases with age.
What are the 4 cells of bones?
1) osteocytes
2) osteoblasts
3) osteogenic cells (osteoproginators)
4) osteoclasts
What are osteoproginators? What is another name for them?
- cells derived from mesenchymal stem cells,
- they give rise to osteoblasts.
- also called OSTEOGENIC CELLS
What are osteoblasts?
- cells which secrete extracellular matrix of the bone
What are osteocytes?
- osteoblasts which do not secrete the ECM anymore
- cells which are surrounded by the secreted extracellular matrix
What are bone lining cells?
- cells that remain on the bone surface when there is no active growth
- derived from osteoblasts that remain after bone deposition ceases
What are osteoclasts?
- bone-resorbing cells present on bone surfaces where bone is being removed, remodeled, or has been damaged.
- macrophages
What is the main difference between the osteoblast and the osteocyte?
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
What types of bone cells make up the canaliculi system?
osteoclasts and osteocytes
osteoCLasts- CanaLiculi systems
