Session 7: Bones, bone marrow, blood & blood vessels Flashcards
Describe the bones of the axial and appendicular skeleton
- 206 bones in total => 80 are axial and 126 are appendicular
- axial = skull, laryngeal skeleton, vertebral column & thoracic cage.
- appendicular = bones that attach to axial skeleton eg bones of shoulder, pelvis & limbs
What are the 2 types of bones?
Cancellous and compact/cortical bone
What is cancellous bone?
- Sponge-like tissue inside bones
- Forms networks of trabeculae (fine bony columns/plates)
- Spaces between trabeculae are filled with bone marrow
What is compact/cortical bone?
Hard outer bone
What are osteoblasts, and what do they do?
Cells derived from mesenchymal stem cells.
They form new bone by laying bone tissue.
How do osteoblasts turn into osteocytes?
Once the osteblasts has surrounded itself with bone matrix, it becomes trapped in lacuna and becomes and osteocyte.
What are osteocytes and what do they do?
They are mature bone cells formed from osteoblasts that maintain bone.
Due to restrictive space, they cannot produce bone tissue
What are the types of cells found in bone?
Osteoblasts, osteocytes, osteoblasts and haematopoietic cells in bone marrow that produce RBCs
What are osteoclasts? What do they do?
- Originate from haematopoietic stem cells
- They break down bone tissue through the release of acid to release hydroxyapatite crystals and collagenase.
- Remodel bone & regulate Ca2+ in blood
What processes is bone formed?
Endochondral ossification and intramembranous ossification
Describe the process of endochondral ossification.
- Produces long bones from a cartilage template
- Continued lengthening is by ossification at epiphyseal plates
- Appositional growth => growth at edges, increases bone width
How do long bones develop?
Long bones require cartilage template to develop by endochondral ossification
Describe the process of intra-membranous ossification.
- Formation of bone from clusters of mesenchymal stem cells in the centre of bone (trabecular of cancellous bone)
- Interstitial growth = growth in the middle, outwards which increases bone length
- Flat bone develops directly from mesenchymal tissue.
What is appositional growth?
Growing at the edges to increase bone width
What is interstitial growth?
Growth in the middle, outwards to increase bone length
Describe in 5 steps how bone trabeculae is formed.
- Osteoblast lays down bone tissue around itself
- Once surrounded by bone tissue, it becomes trapped within bone tissue and turns into osteocyte.
- Cement line = where new bone meets existing bone, more mineral is added so becomes bone and cement line moves
- Hydroxyapatite is deposited
- Osteoclasts resorbs (break down)
What are calcium crystals called?
Hydroxyapatite crystals
Describe the conversion of cancellous bone to cortical bone in 5 steps.
- Mesenchymal cells convert osteoblast that line recently formed trabeculae
- Lay down bone tissue that is mineralised
- Osteoblats trapped => forms into osteocytes
- Steps 1-3 are repeated
- Central mesenchymal cells convert into blood, & lymph vessels and nerves