Locomotor: Bones 1 & 2 Flashcards
Bone functions
- Heamatopoiesis
- Metabolic
- Machanical:
- Structure
- Protection
- Hearing
- Breathing
Heamatopoiesis
The synthesis of blood
- red cells
- white cells
- platelets
Red bone marrow
This is the bone marrow where blood is made it forms the axial skelleton of an adult and entrie skelleton of a child.
Yellow bone marrow
This is found in the long bones of the adult body and contains adipose tissue (fat) which can be released as energy.
Things bone can store
- Calcium
- Phospherus
- Fat
- Acid-base
Bone’s function in homeostatis
Can release and store calcium-phospherus
Can release and store fat/glucose
Mechanical functions of bone
Structural
- Support
- Motion
Soft organ protection
Hearing
Breathing
Spinal adaptations for bipedalism
- Spinal curvature (thoracic kyphosis and cervical and lumber lordosis) in order to to keep everything above the centre of gravity
- Compressible intervertebral disks as shock absorbers
Hip and knee adaptations to bipedalism
- Enlarged hip and knee joints to bear the weight of the upper body
- Weight bearing axis of the hip and knee. The femure passes medially down the body keeping the knees and ankles directly under the body when walking. This means the knee can lock and very little muscles are required to continue standing.
Foot adaptions for bipedalism
The foot is a tripod shape for stability. This arch also then acts as a spring when weight bareing. The ligaments snapp it back into position when weight is released.
Posterior leg adaptations for bipedalism
- The achilles tendon acts a spring releasing energy during planterflexion
- The soleus is used not olny to dorsiflexion but stability when standing hence consists mostly of slow twitch fibres for endurance
Osteogenic cells brief overview and other name
These are precursors to more specialised bone cells and can become different types depending on signal around them.
Also known as osteoprogenitor cells
Cells that osteogenic cells can become
- Adipocytes
- Myocytes
- Chonrocytes
- Osteoblasts
What signals mean an osteogenic cell becomes a chondrocyte or an osteoblast?
If there is movement then they become chondrocytes. If there is no movement osteocytes release the signals RunX2 and Osterix which signal them to become osteoblasts. Hence why it is so importants to keep a fractures still in a cast when healing.
Locations of osteogenic cells
- Bone marrow
- Periosteum
- Endosteum
What is the periosteum
This envelops bones and is a network of blood vessels and nerves that supply the bone
What is the endosteum
This is a membrane which surrounds the bone marrow
Osteoblasts two main functions
- They are involved in bone production by making non-mineralised bone matrix
- Second function is in regulating osteoclasts
How osteoblasts make non-mineralised bone matrix
- When stimulated by PTH they produce type I collagin and alkaline phosphatase (ALP), an enzyme that initiates calcification of the matrix.
- When stimulated by Vit D they produce matrix and ALP
How osteoblasts regulate osteoclasts
- Makes RANK-Ligand in response to PTH which stimulates osteoclast precursors to become osteoclasts therefor increases bone resorption.
- Makes osteoprotogrin (OPG) which binds to free RANK ligands and therefore prevents osteoclast formation and bone resorption
What happens to osteoblasts?
The have a lifespan of 6 months
Afterwhich they either beocme osteocytes in the matrix, flatten on the surface and can once again become mature osteocytes or die off completely via apoptosis
Osteocytes main functions
- Regulate calcium and phosphorus in the bone
- Maintain bone
How do osteocytes maintain bone
- They also release RANK-Ligand like osteoblasts
- Produce sclerostin which inhibit osteoblast formation. Sclerostin is in turn inhibited by PTH and mechanical loading therfore increasing bone production
Osteoclasts
- Multinucleated cells
- Resorb bone
Describe how calcitonin and PTH are involved in calcium homeostasis
PTH is if you don’t have enough calcium and encourages uptake from kidneys and resorption form bones
Calcitonin is if you have too much calcium and this reduces uptake in kidneys and encourages deposition in bone
What is ALP?
What does it do?
What is it a sign of?
ALP stands for alkaline phosphatase
It dephosphorylates organic compounds initiating the calcification of the matrix by laying down deposits of calcium phosphate.
It is a sign of high bone turnover and elevated levels are often found in Paget’s Disease of the Bone
