Bone Flashcards
Name the 5 bone shapes
Long - Limbs
Flat - Skull
Cuboid - Tarsus
Irregular - Vertebrae
Sesamoid - patella
What is the outer and inner layer of bone called
Outer - Lamellar Bone (Found in the cortex) - Compact
Inner - Trabecular Bone (Found in Medulla) - Spongey
What are the two bone membranes
Periosteum (Outer Membrane)
Endosteum (Inner membrane)
Both contain fibroblasts in a collagen matrix which is a source of bone cells for growth and repair
What are the three bone cells and what do they do?
Osteoblasts - (Immature Cells)
Lay down bone by producing osteoid (Type 1 collagen), which is then mineralized
Osteocytes - (Mature Bone)
Needed for maintenance and calcium homeostasis
Osteoclasts
Related to macrophages and dissolve bone
What are the 4 main blood supply to bones?
Epiphyseal arteries
Metaphyseal arteries
Nutrient artery
Periosteal Arteries
The blood supply has many collateral links (anastomoses) which usually ensures a back up blood supply.
The Epiphyseal arteries are a sole supply in growing mammals and only unite with the metaphyseal arteries in the adult. So if any damage to the epiphyseal supply occurs then bone growth may be altered in young mammals
Describe the process of bone growth in 5 steps.
Cartilage cells in the epiphysis multiply and form long columns
Chondrocytes gradually accumulate calcium
As the surrounding matrix calcifies the chondrocytes die
Osteoblasts come along, some remain in the periosteal to line the bone whilst others transition into osteocytes.
Osteoclasts absorb the bone which is already laid down leaving pits which allows the osteocytes to reconstruct new bone.
what is it called when only the periosteum is damaged
Periostitis
What is inflammation of the bone called
Osteitis
What is sequestrum
Bone fragments which loose blood supply and die
Why is over work stress a negative thing during fracture healing
Bone removal is quicker than bone deposition meaning bone strength declines and stress fractures will occur if further pressure is put on the bone.
What are the three phases of fracture healing and what happens in each phase
Reactive Phase =
Damaged blood vessels bleed and form clot
Osteocytes along the fracture line die
Inflammatory reaction occurs
Fibroblasts multiply and infiltrate the clot and produce collagen
Capillaries bud into the clot-collagen mass to create granulation tissue
Repair Phase =
Fibroblasts change into chondroblasts and start to product hyaline cartilage (Type 2 collagen) to bridge the gap.
Osteoblasts mineralize the cartilage to form a callus
Remodeling Phase =
Hyaline cartilage is removed as normal osteons grow into the callus
First proper bone is woven and gradually replaced by lamellar in the cortex and trabecular in the medulla.
The callus is remodeled according to stress (Wolfs Law)
Fracture types (9)
Greenstick
Simple
Oblique
Spiral
Comminuted
Compressed
Longitudinal
Multiple
Articular
What are the 4 key factors needed for good fracture healing
Good blood supply
Intact nerve supply
Stability of the bone
Slight movement of fracture sight (Wolfs Law)
What is the theory behind Wolfs Law
Bone is a crystal which when bent quickly generates a current. Osteocytes detect this current and lay down bone where it is compressed and remove bone where is is under tension. Therefore bone is laid down in natural stress lines within the bone.
During fracture healing slight cyclic loading should be carried out in order for the bone to get stronger and lay down new bone in the right places. Only a few vibrations needed per week.
(Use it or loose it)
