This pre-lecture material is to help you prepare for the lecture and to assist your note-taking within the lecture, it is NOT a substitute for the lecture
Although every effort is made to ensure this pre-lecture material corresponds to the live-lecture there may be differences / additions
Bone
A living tissue with cells and a calcified extracellular matrix
Bone cells
Respond to external forces
Bone remodels and can change shape through your life to reflect how you are using your skeleton
Bone can repair itself
Extracellular components of bone
Organic
Inorganic
Organic component
33% of bone ECM, includes collagen and ground substance, functions to resist tension
Inorganic component
67% of bone ECM, includes hydroxyapatite and other mineral salts, makes bone hard and resistant to compression
Bone cells
Osteogenic cells
Osteoblasts
Osteocytes
Osteoclasts
Osteogenic cells
Stem cells that produce osteoblasts
Osteoblasts
Produce new bone matrix
Osteocytes
Recycle protein and minerals from matrix
Osteoclasts
Remove bone matrix
Bone homeostasis
Balance of bone destruction and formation that means amount of bone stays the same
Types of bone tissue
Compact
Cancellous
Compact bone
Outer surfaces seem dense and impenetrable, made up of circumferential lamellae and units called osteons
Osteon
Longitudinal unit within compact bone, provides a pathway for nutrients to get to cells in the ECM, contains a central canal with blood vessels and nerves, and is formed of a series of cylinders called lamellae
Lacunae
Lakes for osteocytes within the osteon
Canaliculi
Channels for osteocytes through the ECM
Cancellous bone
Contains trabeculae, which are struts of lamella bone with marrow filling the cavities between them
Trabecular bone
Organisation of trabeculae resists force from multiple directions and directs force from body weight in single direction down shaft, spreading force distally
Bone remodelling
1. Osteoblasts add bone matrix in lamellae to bone surface
2. Osteoclasts remove bone from the medullary cavity
Osteoporosis
Loss of cortical bone and thinning of cancellous bone trabeculae, leading to compression fractures of vertebrae
Biological females are more at risk of osteoporosis due to loss of estrogen post-menopause
Lifestyle factors like lack of exercise and nutritional factors can also contribute to osteoporosis risk
Peak bone mass in your 20s determines your risk of osteoporosis later in life