Musculoskeletal - Bone Flashcards
What are the four types of cells present in bone?
1) Osteoprogenitor cells
2) Osteoblasts
3) Osteoclasts
4) Osteocytes
What are osteoprogenitor cells?
They are bone stem cells - they form the osteoblasts
What are osteoblasts? What do they do?
They are bone forming cells.
They line the surface of the bone, secrete collagen which forms the organic matrix of the bone
What is the name for the organic matrix before it is calcified?
Osteoid
What are osteocytes?
They are osteoblasts that have got trapped in the organic matrix.
They communicate with each other via fine processes through canaliculi.
They are involved in bone regulation
What are osteoclasts?
They are large, multinucleated cells with a ruffled border.
Their function is to resorb bone
Osteoclasts are formed from osteoprogenitor cells. True or false?
False - they are formed from monocytes which fuse together to form the multinucleated cells
What is the extracellular matrix made up of?
1) Organic matrix (30%)
2) Collagen (type 1 - 90%, some type V)
3) Water
4) Bone mineral - hydroxyapatite
What properties does calcification give bone?
1) Bending, twisting and stretching resistance
2) Hard
What is the main property collagen fibres give bone?
Resistance to tensile stress
What type of junction is present between osteocytes?
Tight Junctions
What is the the name of the inhibitor of osteoclast activation?
OPG (Osteoprotegerin)
How does PTH lead to activation of osteoclasts?
1) PTH binds to the osteoblast
2) OPG is inhibited
3) Inhibited OPG means RANKL no longer inhibited
4) RANKL on osteoblast binds to RANK on osteoclast
5) Osteoclast is activated
What hormones favour bone formation?
Insulin Growth hormone Insulin-like groeth factor Oestrogen Testosterone Calcitonin
What hormones favour bone resorption?
Parathyroid hormone
Cortisol
Thyroid hormone
Where is parathyroid hormone secreted from?
Parathyroid gland
What cells secrete parathyroid?
Chief cells