Bone Flashcards
What type of tissue is bone?
Connective tissue.
What are the functions of bone?
Weight-bearing and support for mechanical function
Protection
Mineral store
Blood formation (red bone marrow)
Name some types of bone.
Flat, long, sutural, short, irregular, sesamoid.
What is cortical bone?
Compact/hard bone.
What is trabecular bone?
Spongey bone.
Why is bone highly vascularised?
There are many blood vessels.
What is stored in the medullary cavity?
Red bone marrow- produces blood cells.
What are the membranes?
Periosteum (membrane surrounding bone)
Endosteum (inside the membrane)
How is cortical bone arranged?
Arranged in Osteons/Havernious systems- small circular structures with perforating canals around.
What lies around Haversion canals?
Osteocytes and bone matrix lamellae.
How is trabecular bone arranged?
Less dense than cortical bone, no Osteons/Havernious canal systems- have a network of lamellated trabecular which are filled with bone marrow. The orientation of trabeculae reflects the main direction of mechanical force.
What are the two types of bone formation?
Endochondral
Intramembraneous
What is the most common type of bone formation?
Endochondral.
What happens during endochondrial ossification?
The bone forms firstly as a cartilage model.
Blood vessels then invade the cartilage.
The cartilage is replaced with bone- it remains in an epiphyseal growth phase then eventually ossifies.
What distinguishes endochondrial ossification?
Cartiligonous phase.
What happens during intermembranous ossification?
Mesenchymal cells develop into osteoprogenitor cells which mature into osteoblasts and start depositing bone.
Residual mesenchymal cells deposit blood and bone marrow.
This bone formation also occurs in adult cortical bone.
What is bone composed of?
Cells (osteoblasts/osteocytes/osteoclasts)
Extracellular matrix
Minerals
Collagen
What are the 3 types of cell in the bone?
Osteoblasts
Osteocytes
Osteoclasts
What is the bone extracellular matrix composed of?
45% hydroxyapatite crystals (complex form of calcium phosphate), water, collagen.
What do minerals do in the bone?
Stiffen / rigidify structures.
What does collagen do?
Gives support and flexibility- reduces the risk of fracture because it has a high threshold of tension.
What does healthy bone have a balance of?
Bone remodelling- removal/formation.
Is bone remodelling a constant process?
Yes- even in adult bone.
What do osteoclasts do?
Reabsorb bone matrix.
Where are osteoclasts found?
Surface of bone mineral.
What do osteoblasts do?
Role in initial bone formation and bone remodelling.
Where are osteoblasts found?
Periosteum / endosteum
What do osteocytes do?
Maintain the mineral concentration through enzyme secretion.
Where are osteocytes found?
Lacunae.
Name some disorders of bone remodelling.
Osteoporosis, osteopetrosis, Paget’s disease.
What is bone mass controlled by?
Genetics and environment.
What else can affect bone mass/
High mechanical load (eg. athletes).
