What is the nasal fossa?

• A. A bone in the skull.
• B. The air-filled cavity of the nose.
• C. A muscle of facial expression.
• D. A nerve canal.

Answer: (B)

The nasal fossa is the air-filled cavity inside the nose—the nasal cavity. It isn’t a bone, a muscle, or a nerve canal; those describe a skull bone, a facial muscle, and a bony passage for nerves, respectively. The nasal cavity is lined with mucous membrane and cilia, warms and humidifies inspired air, and communicates with the throat posteriorly through the choanae. It’s divided into two halves by the nasal septum and bordered by the surrounding bones, with the floor formed by the hard palate and the lateral walls housing the turbinates to increase surface area and airflow contact. This is why the nasal fossa refers to the air-filled cavity of the nose.