Skeletal System: Bone Growth Quiz

Ossification that begins as hyaline cartilage that is subsequently replaced by bone tissue.

Endochondral Ossification

Builds cartilage.

Chondrocytes

Builds bones.

Osteoblasts

Break down bones.

Osteoclasts.

Step 1.

Development of cartilaginous model.

• Cells gather in the site where the bone will form and become chondroblasts.

• Structure is covered by perichondrium.

Step 2.

Label the outer layer:

Growth of cartilage model

• Chondroblasts are now called chondrocytes. Chondrocytes increase in size.

• Cartilage begins to calcify and die. 

• Label: Perichondrium

Step 3.

Label (from top to bottom)

Formation of primary ossification center

• Small cavities become the primary ossification center. A nutrient artery appears in the center.

• Osteoblasts begin to form spongy bone.

• Perichondrium is now called the periosteum because bone is present.

• Labels: primary ossification center, nutrient artery, periosteum.

Step 4. 

Development of the medullary cavity

• Wall of diaphysis is replaced with compact bone.

• Osteoclasts break down spongy bone and begin to form the medullary cavity.

• Spongy bone remains present in the epiphysis and is not replaced with a medullary cavity or compact bone.

• Primary ossification center expands to ends of bone.

• Label: Medullary Cavity

Step 5.

Formation of the secondary ossification center

• Secondary ossification centers form in the epiphysis.

• Medullary cavity fills with red bone marrow.

• Label: Secondary ossification center.

Step 6.

Formation of articular cartilage and epiphyseal plate

• Line of cartilage remains between the epiphysis and diaphysis until adulthood.

• Labels: 1 - Epiphyseal Line, 2 - Articular Cartilage

How is intramembranous ossification different from endochondral ossification? Which bones grow this (intra) way?

Intra - bone that forms from fibrous connective tissue.

• Bones of the skull

Endo - bone that forms from cartilage tissue.