What are the 2 parts of the skeleton?
axial
appendicular
functions of the bones?
movement Protect organs Strength store calcium blood cell production
What is the bone composed of?
70% inorganic salts
30 organic component (90% collagen type I)
What is the mineral component of bone?
calcium hydroxyapatite- gives rigidity and strength
What are the cellular componets of bone?
osteoclasts
osteoblasts
osteocytes (for structure)
What are the different bone shapes?
long bone short bone flat bone irregular bone sesamoid bone
What are the 2 types of bone?
compact bone
trabecular bone
Outline bone dev and growth
- Intramembranous ossification- mesenchymal cells differentiate into osteoblasts which synthesize osteoid.
a. Mineralisation of osteoid
b. OBs entrapped in lacunae
c. Osteoprogenitors produce more OBs
d. Eventually fusion of adjacent ossification centres to form bone is spongy
e. Primitive mesenchyme in network of dev bone diiferentiates into bone marrow - Endochondral ossification (In long bones, vertebrae, pelvis)- SEE DIAGRAMS
What are neurovascular channels called?
Canals of Havers/ Haversian canals
What do osteoblasts do?
- Secrete bone matrix (deposition of osteoid)
2. Transformed into osteocyte
What are osteocytes and what do they do?
They’re mature osteoblasts that become trapped in osteoid
- Occupy spaces in osteon lamellae called lacunae
- Maintain structural integrity of bone
What are osteoclasts
Phagocytic bone cells (refashion bone)
They secrete organic acids and lysosomal enzymes
How do osteoclasts maintain calcium homeostasis?
- Skeleton is storage site for calcium
- Parathyroid hormone released when low level calcium in blood
- This stimulates osteoclasts to breakdown bone to add calcium to blood
- When the blood has a high level of calcium, the thyroid c cells release calcitonin which stops the osetoclasts, and calcium levels in blood decrease.
