What happens to an osteoblast once it becomes surrounded by the matrix it has made?

It stops secreting new matrix and becomes an osteocyte, sitting in its own lacuna and maintaining the bone tissue around it.

What does an osteoclast do?

An osteoclast is a large cell with several nuclei that secretes acid and enzymes to dissolve the bone matrix, releasing calcium and phosphate ions into the blood.

What happens to the bone of a limb that has been immobilised in a plaster cast for several months?

Without the mechanical loading that normally stimulates the bone-forming cells, breakdown outpaces deposition and the bone loses mass and density.

Which balance decides whether a bone gains or loses mass?

It is decided by the relative activity of the osteoblasts laying down matrix and the osteoclasts dissolving it away.

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Biological Molecules

Topic overview Inorganic ions and the properties of water Monosaccharides and disaccharides Polysaccharides, storage and structure Lipids, triglycerides and phospholipids Amino acids and protein structure Condensation, hydrolysis and the food tests

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Human Musculoskeletal Anatomy: Skeletal TissuesMusculoskeletal

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Neurobiology and Behaviour: The BrainNeurobiology

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Human Musculoskeletal Anatomy: Skeletal Tissues

Bone remodelling and the Haversian system

3 things to know
Component 3

Overview

Haversian system and function of the Volkmann's canals that cross a bone.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why can no osteocyte lie far from a Haversian canal?

Key term

What does an osteoblast do?

Key term

Why must bone be broken down and rebuilt continuously throughout life?

Questions from this subtopic

Each one with the model answer underneath.

1
What does an osteoblast do?
Model answer
An osteoblast secretes the organic collagen matrix of new bone and then deposits the inorganic calcium and phosphate salts within it.
2
What happens to an osteoblast once it becomes surrounded by the matrix it has made?
Model answer
It stops secreting new matrix and becomes an osteocyte, sitting in its own lacuna and maintaining the bone tissue around it.
3
What does an osteoclast do?
Model answer
An osteoclast is a large cell with several nuclei that secretes acid and enzymes to dissolve the bone matrix, releasing calcium and phosphate ions into the blood.
4
Why must bone be broken down and rebuilt continuously throughout life?
Model answer
Continuous remodelling repairs the microscopic cracks that accumulate under load, allows the shape and thickness of a bone to change in response to the forces acting on it, and lets the skeleton act as an adjustable store of calcium.
5
What happens to the bone of a limb that has been immobilised in a plaster cast for several months?
Model answer
Without the mechanical loading that normally stimulates the bone-forming cells, breakdown outpaces deposition and the bone loses mass and density.
6
Which balance decides whether a bone gains or loses mass?
Model answer
It is decided by the relative activity of the osteoblasts laying down matrix and the osteoclasts dissolving it away.

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