Final answer:
The primary bone underlying the cheek is the zygomatic bone.
Step-by-step explanation:
The primary bone underlying the cheek is the zygomatic bone. Also known as the cheekbone, the zygomatic bone forms much of the lateral wall of the orbit and the lateral-inferior margins of the anterior orbital opening. It projects posteriorly to form the anterior portion of the zygomatic arch. The zygomatic arch is the bony arch on the side of the skull that spans from the area of the cheek to just above the ear canal.