Lecture 13: Bone, BM, vessels & blood Flashcards
Name the bone functions.
-Mechanical: protect tiss/organs
framework for overall body shape
levers for movement
-Synthetic: haemopoiesis
-Metabolic: mineral storage (Ca2+, P)
Fat storage (yellow BM)
Acid-base homeostasis (regulate blood pH)
What are the 2 types of bone called and where can you find them?
Cancellous/Trabecular bone: spongey, fine trabeculae with many spaces filled with BM; found in the internal spaces.
Compact/Cortical bone: mineralised hard bone making up 80% skeletal mass; forms the external surfaces.
Describe the 2 types of ossification.
Endochondral: forms the long bones of the body from a cartilage template.
Intra-membranous: forms flat bones from mesenchymal stem cells in the cancellous bone: interstitial growth (centre –> out)
Briefly describe what you would see in a histogram of intramembranous ossification.
Most likely a histogram of flat bone growth.
- periosteum surrounding the newly formed bone
- osteoblasts lining the mesenchymal tiss. (almost like epithelia)
- osteocytes embedded within the newly formed bone
- multinucleated osteoclasts on the edge of mesenchymal tiss.
- might find new bone spicule in the middle of mesenchymal tiss, as interstitial growth
What is an osteocyte?
A bone cell (osteoblast) surrounded by new osteoid (bone substance).
What is an osteoblast?
A cell that secretes osteoid so is responsible for new bone formation.
What is an osteoclast?
A large multinucleated bone cell which remodels bone by releasing enzymes.
How is cancellous bone converted into cortical bone?
- MSC develop into osteoblasts that form trabeculae.
- They lay down osteoid that is mineralised.
- Osteoblasts within osteoid become osteocytes
- Steps 1-3 are repeated to form non-parallel lamellae (rings)
- Central MSC are converted into Haversian & Volkmann’s canals.
- This forms an osteon.
Structurally, what is the difference between immature and mature bone?
Immature bone has osteocytes in random arrangements.
Mature bone has osteocytes arranged in concentric lamellae in osteons.
Describe the reabsorption canals in mature bone.
They run parallel to the osteon long axes and act as the starting point of bone remodelling.
Describe the structure of compact bone.
Concentric lamellae in osteons
Haversian and Volkmann’s canals
Periosteum membrane surrounding bone
Describe the structure of trabecular bone.
Spaces filled with BM
Osteocytes lie between lamellae
No Haversian or Volkmann’s canals
Osteoblasts/clasts peripheral to lamellae
What do the Haversian and Volkmann’s canals carry?
Blood, lymph vessels and nerves.
Describe the composition of bone.
65% minerals
23% collagen 1
10% water
2% other proteins
How can bone resist relatively great tension and fractures?
Bones have high tensile, compressive strength and is quite flexible: water between the lamellae so the lamellae can slip over each other. Reduces excessive force so bone more resistant.
Epiphysis (end of long bone) is larger than the shaft (diaphysis) so applied force is spread out at the opposite end.