Bone Formation, Growth,
Remodeling
Repair of Bone Fractures
Page 121 to 124
Connective Tissues

Cartilage



Embryos: hyaline cartilage
Young child: cartilage replaced by bone except
bridge of nose, parts of ribs, and joints.
Bone

Ossification: bone formation
Bone Formation


Hyaline cartilage is covered with bone matrix
by osteoblasts (bone forming cells).
The enclosed hyaline cartilage is digested
away, opening up a medullary cavity within
the newly formed bone.
Bone Formation

By birth, most hyaline cartilage have been
converted to bone except for two regions


Articular cartilages
Epiphyseal plates
Articular Cartilage


Persist for life.
Reduces friction at the joint surfaces.
Epiphyseal plates



Provide longitudinal
growth of the long bones
during childhood.
Growth controlled by
growth hormones and sex
hormones (during
puberty).
Completely converted to
bone during adolescence.
Bone is an active tissue.


Responds to calcium levels.
Pull of gravity and muscles.
Calcium Levels

Decrease



parathyroid hormones (PTH) are released
Activates osteoclasts (giant bone-destroying
cells.
Increase (hypercalcemia)



Calcium from the blood is deposited in the bone
matrix as hard calcium salts.
May cause renal or bladder stones
May be a sign of other diseases
Pull of gravity and muscles


Bones where bulky muscles are attached
become thicker and form large projections.
Inactivity causes loss of mass and atrophy in
bones due to lack of stress.
Repair of Bone Fractures




Hematoma (blood-filled swelling) is
formed.
The break is splinted by a fibrocartilage
callus (mass of repair tissue).
The bony callus (made of spongy bone) is
formed.
Bony callus is remodeled in response to the
mechanical stresses placed on it, so that it
forms a strong permanent “patch” at the
fracture site.