Bone and Fracture Repair Flashcards
What is the difference between intramembranous ossification and endochondral ossification?
IMO: THICKENING, at mesenchymal tissue to form compact bone
EO: replacement of pre-existing hyaline cartilage template by compact bone
How does intramembranous ossification take place?
- Mesenchymal stem cells –> osteoprogenitor cell –> osteoblasts,
- osteoblasts lay down osteoid (ECM: collagen I)
- osteoid calcifies forms spicules
- spicules form trabeculae which are replaced by lamellae of compact bone
What are the two types of bone?
COMPACT: external surfaces, osteons = successive concentric lamella – resists bending – osteocytes spread between. At the centre is the haversian canal: contain blood vessels/nerves.
TRABECULAR: resists compression – osteocytes/bone marrow spread between, sense changes in strength, covered in lining cells, no haversian or Volkmann canals
What is the difference between immature vs mature bone?
I –> random osteocytes, M –> osteocytes arranged in concentric lamellae of osteons, resorption canal runs parallel with osteons’ long axes
Where is the site of haematopoiesis?
Bone marrow
Which type of bone contains blood vessels?
Compact/cortical
What is the role of osteoclast?
multi-nucleated cells, absorb bone, anchor to the surface of bone, ‘sealed-zone’ between osteoclast and bone, microenvironment, H+ and lysosomal enzymes: dissolves bone mineral content, enzymes then remove collagen matrix
Describe what an osteoblast does
refill resorption cavities, deposit osteoid (collagen, Ca, phosphate begin to crystallise), some become trapped becoming osteocytes, some undergo apoptosis, some become lining cells on the surface of bone
What is osteocyte?
Osteocytes: complex network throughout bone, sense increase workload on bone = trigger activation of osteoblasts. Reduced loading = resorption/remodelling increase to eliminate under-loaded bone
What are the stages of bone repair when a break has occurred?
Break: bleeding = haematoma (eventually removed by macrophages), inflam, granulation tissue arises, blood vessels infiltrate, hyaline cartilage = fibrocartilaginous callus, Endochondral/intramembranous ossification = trabecular bone, remodelled to compact bone, bulging removed by osteoclasts
What are the risk factors for osteoporosis?
age, female, post-menopausal, insufficient Ca intake, insufficient Ca absorption and Vit D, low exercise, smoking, genetic
What is osteoporosis?
Metabolic bone disease = mineralized bone is decreased in mass, no longer provides support. Changes –> enhanced bone resorption, incomplete filling of osteoclast resorption bays, loss of mass in trabecular = increased risk of fracture
What is the difference between type 1 and type 2 primary osteoporosis?
Primary osteoporosis type 1: post-menopausal women = increase in osteoclast number = oestrogen withdrawal. Primary osteoporosis type 2: elderly, both sexes (senile osteoporosis), reflects attenuated osteoblast activity
What is periosteum?
Dense connective tissue enveloping bone except at the surface of joints
What is diaphysis?
Shaft of bone
