Connective tissue - Bones Flashcards
What are the different parts to a long bone and their purpose?
What do each of these things do?
Lacunae: house the osteocytes (mature bone cells).
Canaliculi: aid in communication between the osteocytes.
Osteons are formed by ________ lamellae. Gaps between the bony tubes are filled with _________ _________.
The _________ canal is lined with _________.
concentric, interstitial lamellae
Haversian, endosteum.
What is within the Haversian canal?
Why is it that an osteocyte can live even when it isn’t right next to the Haversian canal?
A couple of capillaries (with fenestrated endothelium), a few unmyelinated axons.
No osteocyte is far from a diffusion as the size of an osteon can only get up to 400micrometers in diameter.
How is trabecular bone arranged? How do the cells get nutrients?
Is still lamellar but has no osteon arrangement.
No blood vessels but are fueled by diffusion from marrow vessels.
Function of periosteum?
Function of endosteum?
What is the organic and inorganic part of bone?
Organic: Type 1 collagen.
Inorganic: Hydroxyapitate which is mineralised to be strong.
Explain what each of these cells do?
How do the red turn into the orange?
Endosteal lining contains most cells.
Row of red cells: osteoblasts=bone forming, derrived from embryonic mesenchyme, they are protein secreting cells (ground substance and connective tissues), they form the osteiod. They also have actin and myosin fillaments, this allows them to move. They secrete the osteoid/matrix around them. They eventually are trapped by their own bone formation and this also pushes each of them away. Once they have been trapped they slow down and mature to become osteocytes.
Through canaliculi they can contact each cell via gap junctions, this allows them to maintain the metabolic continuity.
Big purple one is the osteoclast (contain several nuclei): bone breaking cells. They are derrived from the bone marrow (myeloid lineage, NOT from embryonic mesenchyme). Dissolved minerals and destroys osteoid.
What are the two mechanisms of bone formation?
Membranous (formation of the skull) and endochondral (long bones like the femur).
Explain endochondral bone formation?
Endochondral ossification: Template model of hyaline cartilage, this then gradually becomes bone.
Central part of cartilage the chondroblasts will swell and die and it will calcify. In the middle the cartilage is modified to bone, this is called the primary ossification centre (one primary ossification centre for each long bone). This then spreads outward.
The same thing will happen at the ends of the long bones and this is called the secondary ossification centres.
Explain intramembranous ossification?
Direct formation of bone from a vascularised sheet. Mesenchymal cells become osteoprogenitor cells.
Explain the vascularisation of bone?
