bones Flashcards
Bones and teeth are unique tissues that incorporate
bothorganic and inorganic components.
The organic component of bone is mostly collagen a
stretchy protein also found in cartilage, tendons, ligaments, and skin. Collagen is the source of the elasticity, flexibility, and strength of bones. Without collagen, bone would be very brittle.
The inorganic component of bone is a form of
hydroxyapatite‡ – a type of calcium phosphate.
It is the bone minerals – deposited within a
collagen matrix – that gives bone its stiffness.
Most bones are about 60-70%
mineral.
Bones with higher mineral density are stiffer, but more
brittle, and less dense bones are strong, but less stiff.
Bone tissue comes in two main forms:
compact (cortical) and trabecular (spongy or cancellous).
Compact bone is densely packed and is found where
mechanical strength is required.
Trabecular bone provides structural support without adding too much weight, is involved with maintaining
calcium and phosphate levels in the body, and houses red blood cell production.
Bones develop in one of
two ways
In endochondral bone development, a
cartilage “model” forms first and is replaced by bone
in intramembranous bone development, bone
directly develops within connective tissue without a cartilage precursor.
Most bones follow the
endochondral development pathway.
Bones that follow the intramembranous developmental pathway are all
flat bones and include many of the bones of the skull as well as the clavicles (collarbones).
Bone is a living tissue that is constantly being replaced and regenerated (adults replace about 10% of their bone material every year) and bone also remodels and reshapes itself in response to activity.
