Bone Cells Flashcards
Describe bone turnover.
A constant process.
Osteoclasts break down old bone.
Osteoblasts build up new bone.
What is the structure of osteoclasts?
Large multinucleate cells.
Derived from haematopoietic stem cells.
Found on the bone surface.
What is the function of osteoblasts?
Has a ‘ruffled border’ that releases acid and resorbs bone matrix.
What is another term for resorption pits?
Howship’s lacunae.
What is the structure of osteoblasts?
Immature bone cells.
Derived from osteoprogenitor cells in the periosteum and endosteum.
What is the function of osteoblasts?
Produces a bone matrix and initiates calcification.
Define the unmineralised matrix produced by osteoblasts.
Osteoid.
A gelatinous substance made up of collagen and mucopolysaccharides.
What is the structure of osteocytes?
Mature bone cells.
Osteoblasts surround themselves in matrix.
Found inside Howship’s lacunae.
What is the function of osteocytes?
Has many extensions lying in canaliculi.
Connects lacunae to each other for communication.
May maintain bone matrix.
Describe the extracellular matrix of bone.
Collagen fibres are strongly cross-linked with large gaps, for minerals to ‘scaffold’ on.
Water is also present.
The fibre orientation is linked to mechanical forces.
Give a few examples of bone disorders.
Osteoporosis (resorption > formation).
Paget’s Disease (increased resorption and formation).
Osteopetrosis (resorption < formation).
How can bone mass change?
Controlled by genetics and the environment.
Regulated by mechanical loads.
Oestrogen in females reduces the number of osteocytes, so females lose bone mass faster.
Define endochondral ossification.
The bone forms a ‘cartilage model’.
Blood vessels invade the cartilage.
Ossification centres form.
Bone replaces the cartilage and ossifies.
Hyaline cartilage remains in the epiphyseal growth plate.
Define intramembranous ossification.
Mesenchymal cells develop into osteoprogenitor cells that mature into osteoblasts.
Bone is deposited.
Residual mesenchymal cells develop blood vessels and bone marrow.
Define appositional bone growth.
Old bone is reabsorbed.
New bone tissue grows beneath the periosteum.
Bone diameter increases.
