Question

What is intramembranous ossification? List and describe the 4 phases of this process.

A) Intramembranous ossification occurs in long bones.
B) Phase 1 is the formation of a cartilage model.
C) Phase 2 involves the replacement of cartilage with bone.
D) Phase 3 is known as the primary ossification center.

Answer 1

Intramembranous ossification is the process of bone development from fibrous membranes. It occurs in the formation of flat bones like the skull, mandible, and clavicles. The four phases of intramembranous ossification are the formation of a cartilage model, replacement of cartilage with bone, development of trabecular matrix and periosteum, and the formation of compact bone and red marrow.

Step-by-step explanation:

Intramembranous ossification is the process of bone development from fibrous membranes. It occurs in the formation of flat bones like the skull, mandible, and clavicles. Here are the four phases of intramembranous ossification:

1. Formation of a cartilage model: Mesenchymal cells group together and form clusters, creating ossification centers.
2. Replacement of cartilage with bone: Osteoblasts, which are specialized cells, secrete an extracellular matrix called osteoid. This osteoid hardens the matrix by depositing calcium, forming spongy bone.
3. Development of trabecular matrix and periosteum: Trabecular matrix forms within the spongy bone, and periosteum, a connective tissue, develops around it.
4. Formation of compact bone and red marrow: Compact bone develops superficially to the trabecular bone, creating a thin layer, while crowded blood vessels within the matrix condense to form red marrow.