Flashcards in Musculoskeletal System Deck (99)
What are the 6 functions of bone?
Calcium and phosphorous reserve
Haemopoiesis - red BM
Fat storage - yellow BM
What are the 3 main functions of the axial skeleton?
Heamopoiesis - Red BM
What are the 3 main functions of the appendicular skeleton?
Yellow bone marrow
What part of the bone forms the joint?
What part of the bone forms the junction?
What part of the bone forms the shaft of the bone?
Describe the structure of the epiphysis:
On the outside is articular cartilage, then compact bone, then spongy bone. There are blood vessels inside the compact bone and in between the trabeculae which are plates and rods in the spongy bone that are covered in endosteum. The spaces in between the spongy bone are called the medullary cavity and are most likely to become red bone marrow
Describe the structure of the diaphysis:
It is a cylinder with a hollow centre called the medullary cavity where bone marrow is found. It is lined with endosteum which is a thin inner fibro-cellular layer. Then there is a layer of compact bone. Then a layer of periosteum which contains blood vessels, nerves and sharpeys fibres (collagen fibres) that blend with the endosteum
Why is there such a difference in shape between the epiphysis and the diaphysis?
The forces on the epiphysis are perpindicular to the surface so it doesn’t need a hard shell, but it needs trabeculae for extra support. The forces in the diaphysis are parallel so there is no need for trabeculae but they need a hard outer layer.
What is the extracellular matrix of bones made up of?
Fibres (organic) 1/3 DW
Ground substance (inorganic) 2/DW
What are the fibres (organic) of bone and what forces do they resist?
Collagen fibres (type 1 and 5) which is thick and strong
Resists tension - stretching/pulling
What is the ground substance of bone and what forces does it resist?
Hydroxyapatite - calcium and phsophorus
Resists compression - squeezing/crushing
What are the cells in bone and what forces do they resist?
Resist torsion (twisting)
What is the precursor for osteogenic cells?
Unspecialised stem cells (mesenchyme embryonic CT)
What is the precursor for osteoblasts?
What is the precursor for osteocytes?
What is the precursor for osteoclasts?
Fusion of many monocytes (WBC) progenitor cells (syncitium)
What is the location of osteogenic cells?
The surface of bone in the periosteum and endosteum. Also found in the central canals of compact bone
What is the location of osteoblasts?
Usually in a layer under the active periosteum or endosteum. Found where new bone is being formed
What is the location of osteocytes?
Trapped within laccunae of bone. They can communicate with neighbouring cells through their long cellular processes through canniliculi
What is the location of osteoclasts?
At sites where bone reabsorption is occurring
What is the function of osteogenic cells?
Normally dormant but can divide and supply developing bones with bone forming cells
What is the function of osteoblasts?
Synthesis, deposition and calcification of osteoid
What is the function of osteocytes?
Bone tissue maintenance. They are a live lattice inside bones, localised minor repair and rapid Ca2+ exchange
What is the function of osteoclasts?
Secrets acid and enzymes. Dissolves the mineral and organic components of bone. They have a ruffled border to increase SA and seals on to create a microenvironment and destroy
Bone remodelling = ?
Apositional growth (+) + bone reabsorption (-)
How do long bones grow?
Describe the 4 steps of bone remodelling:
1. Resting periosteum (only osteogenic cells)w/ nerves and blood vessels. Osteocytes are in the lacunae w/ cellular processes in caniliculi
2. Periosteum is now active. Osteogenic cells divide forming osteoblasts which deposit osteoid. Monocyte progenitor cells leave BV and fuse on bone surface
3. Some osteoblasts become trapped in lacunae eventually becomin osteocytes. Osteoclasts form and start dissolving bone
4. When growth stops, osteoblasts can convert back to osteogenic cells or die. The osteoid is fully calcified. Osteoclasts die (apoptosis) so reabsorption stops. Blood vessels grow into the new space.
What is rickets?
A disease in which children do not get enough calcium or vit D. They cannot correctly calcify their bones. It is called osteomalacia in adults