Bones
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State the 4 functions of bone
Weight bearing/support Protection Mineral store Blood formation
The gross anatomy of the bone includes (6)
Compact bone Spongy (trabecular)bone Blood vessels Medullary cavity Bone marrow Membrane (periosteum and endosteum)
What is compact bone organised into?
Circular structures known as osteons surrounding a central Haversian canal
What canals run horizontal in bone?
Volkmann’s canals
What is found around a Haversian canal?
Osteocytes and concentric ring of bone matrix known as lamellae
What are the other names for spongy bone? (3)
Trabecular Cancellous Diploe
Compared to compact bone, spongy bone is ________ dense
Less
What is spongy bone?
A network of lamellated trabeculae filled with bone marrow
What does the orientation of trabeculae reflect?
Main directions of mechanical force
State the 6 types of bone
Flat bone Sutural bone Short bone Irregular bone Sesamoid bone Long bone
What are the 2 types of bone development?
Endochondral Intramembranous
Explain the process of endochondral ossification
Cartilage models of bones are formed. Blood vessels then invade the cartilage. The cartilage is then replaced with bone. The cartilage remains in the epiphyseal growth plate and the growth plate eventually ossifies
Explain the process of intramembranous ossification
There is no cartilaginous phase. Mesenchymal cells develop into osteoprogenitor cells that mature into osteoblasts that start depositing bone. Residual mesenchymal cells develop blood vessels and bone marrow
The bone formation that occurs in adult cortical bone is
Intramembranous ossification
All bones are derived from
Mesenchyme (embryonic connective tissue)
State what makes up bone
Cells which include osteocytes, osteoblasts and osteoclasts And extracellular matrix which includes ~45% hydroxyapatite crystals ~35% Collagen (Type I) ~20% Water
What do minerals such as hydroxyapatite do in bone?
Makes bone stiff and able to support structures. Also gives high strength under compression 3 S’s - Stiffness, support and strength
What does collagen do in bone?
Gives the bone high tensile strength and gives the bone flexibility and reduces the risk of fracture
What makes a bone healthy?
A balance between bone removal and bone formation
What are osteoblasts?
Immature bone cells created from osteoprogenitor cells in periosteum and endospteum
State the function of osteoblasts
To produce bone matrix and initiate calcification
What happens to osteoblasts when they become surrounded by matrix
They become osteocytes
What are osteocytes?
Mature bone cells found inside lacunae
What do canaliculi do?
Connect lacunae together and so allow communication between cells