In sutures, there is proliferation of connective tissue followed by replacement of bone. This is called:

 # In sutures, there is proliferation of connective tissue followed by replacement of bone. This is called:

A. Endochondral bone growth

B. Intramembranous growth

C. Appositional growth

D. Periosteal growth

The correct answer is B. Intramembranous growth.

During the fourth month in utero, there is an ingrowth of blood vascular elements into various points of the chondrocranium (and the other parts of the early cartilaginous skeleton). These areas become centers of ossification, at which cartilage is transformed into bone in the process called endochondral ossification, and islands of bone appear in the sea of surrounding cartilage. The cartilage continues to grow rapidly but is replaced by bone with equal rapidity. The result is that the amount of bone increases

rapidly and the relative (but not the absolute) amount of cartilage decreases. Eventually, the old chondrocranium is represented only by small areas of cartilage interposed between large sections of bone, which assume the characteristic form of the ethmoid, sphenoid, and basioccipital bones. Growth at these cartilaginous connections between the skeletal bones is similar to growth in the limbs.

Not all bones of the adult skeleton were represented in the embryonic cartilaginous model, and it is possible for bone to form by secretion of bone matrix directly within connective tissues, without any intermediate formation of cartilage. Bone formation of this type is called intramembranous ossification. This type of bone formation occurs in the cranial vault and both jaws. 

Ref: Contemporary Orthodontics, William R. Proffit