During intramembranous ossification, what type of bone forms first and is later replaced by lamellar bone?

• A. Lamellar bone.
• B. Woven bone.
• C. Compact bone.
• D. Spongy bone.

Answer: (B)

In intramembranous ossification, the first bone that forms is woven bone. Mesenchymal cells differentiate into osteoblasts that lay down osteoid, which mineralizes quickly into a disorganized, lattice-like bone called woven bone. This immature bone provides a rapid scaffold for growth and healing. Over time, remodeling by osteoclasts and osteoblasts turns the woven bone into lamellar bone, where collagen fibers are organized into parallel layers (lamellae) for increased strength. From there, the mature bone can become compact on the outer surfaces and spongy (trabecular) inside, but the initial product is woven bone. Lamellar, compact, and spongy bones describe mature forms, not the first step.