What’s happening in each zone recap?
1. Resting zone is an anchor for the rest of the epiphyseal region.
 Randomly dispersed chondrocytes in lacunae.
 The youngest tissue, which will converted to trabeculae?
2. Proliferation (growth) zone is the mitotic zone (abuts resting zone)
 Cells form into stacks
 Younger cells at the top where cell maturation occurs
 older cells begin to divide pushing epiphysis away from the diaphysis
 long bone lengthens
3. Hypertrophy (enlarge) (where cells eventually die)
 Older chondrocyte cells closest to diaphysis enlarge
 Lacunae erode and enlarge
 Alkaline phosphatate (which helps with calcification) released here but not active
till next zone
4. Erosion (calcification)
 Osteoclast and osteoblast most active here acting together (3rd location where
these 2 work together).
 Osteoclast punching holes in matrix while osteoblast lays down new bone
 Alkaline phosphate speeds up calcification
5. Diaphysis (ossification)
 Bone being pushed into ossification zone as a result of osteoblast and osteoclast
above
 Osteoblast and osteoclast both active here too
 Process of deposition and resorption occurring on outer edges of compact bone
layer
 Remodeling occurring
 Hematopoiesis blood cell formation produced here (especially in neck & head of
femur). This is where red marrow is layed down.
 This is a primary area for stem cells to be taken from (stem cells in the form of
hemocytoblast cells, which is what is laying down the blood itself)