Intramembranous Ossification

• Use Fig. 8-13 to locate regions of intramembranous bone development in the sections of fetal rodent head on slide 130.
• Identify the periosteum and as many of the bone cells as possible.

What is the difference between osteoid and woven bone?

Endochondral Ossification

• Locate the cartilaginous region on slide 34. (This is not a typical epiphysis of a joint, like that shown in Junqueira's presentation of endochondral ossification.)
• On the slide carefully study all areas of the growth plate, as shown in Figs. 8-14 through 8-17, moving from the cartilage to the diaphysis of the bone. Click to enlarge image.
• Concentrate on the chondrocytes and matrix, noting the changes in these structures as you move through the various functional zones.
  • zone of reserve cartilage
  • zone of chondroblast proliferation
  • zone of chondrocyte hypertrophy
  • zone of cartilage calcification and chondrocyte degeneration
  • zone of osteogenesis

Clinical note: Achondroplasia is an inherited disorder in which there is reduced proliferation of the chondrocytes in the epiphyseal plate of long bones. The result is a form of dwarfism in which the trunk is of normal length, but the extremities are short. Describe in your own words the steps by which cartilage is formed and then replaced by bone during this developmental process. (This is important.)   Now for joints.