Bone Cells Flashcards
Describe bone turnover.
Osteoclasts break down old bone; osteoblasts build up new bone.
Describe the structure of osteoclasts.
Large multinucleate cells derived from haematopoietic stem cells found on the bone surface.
Why do osteoclasts have a ‘ruffled border’?
Releases acid and resorbs bone matrix.
Where are osteoclasts found?
In resorption pits - Howship’s lacunae.
Describe the structure of osteoblasts.
Immature bone cells are created from osteoprogenitor cells in the periosteum and endosteum.
What are the functions of osteoblasts?
Produces a bone matrix and initiates calcification.
Name and describe the unmineralised matrix made by osteoblasts.
Osteoid - a gelatinous substance made up of collagen and mucopolysaccharides.
Describe the structure of osteocytes.
Mature bone cells are found inside lacunae, formed from osteoblasts that surround themselves in the matrix.
What are the functions of the extensions that osteocytes have?
Canaliculi connect to one another for communication.
What is the function of osteocytes?
Maintains bone matrix.
Describe the structure of the extracellular matrix.
Collagen fibres are cross-linked with large gaps. The gaps provide space for crystals to ‘scaffold’ on.
Describe osteoporosis in terms of resorption and formation.
Resorption > formation.
Describe Paget’s Disease in terms of resorption and formation.
Increased resorption and formation.
Describe osteopetrosis in terms of resorption and formation.
Resorption < formation.
Describe endochondral ossification.
The bone forms a ‘cartilage model’. Blood vessels invade the cartilage and form ossification centres. Bone replaces the cartilage.
