Dentinal tubules are filled with which of the following that reside inside the pulp?

• A. Odontoblastic processes
• B. Nerve fibers
• C. Blood vessels
• D. Fibroblasts

Answer: (A)

Dentinal tubules are occupied by extensions from odontoblasts that originate in the pulp. These odontoblastic processes grow from odontoblasts located at the dentin–pulp border and extend through the dentin inside the tubules. Their cell bodies stay in the pulp, but their cytoplasmic processes fill the tubules, linking the pulp to the dentin and playing a key role in dentin formation and sensory signaling.

Nerve fibers, blood vessels, and fibroblasts are components of the pulp tissue itself, not the tubules. While nerves run through the pulp and may reach the dentin near the tubules, they do not fill the tubules. Blood vessels and fibroblasts are also located in the pulp rather than inside the dentinal tubules.