The structure indicated is the middle nasal concha.

There are three nasal conchae which make up the lateral wall of the nasal cavity. The nasal conchae are curved bones which create channels for the flow of air through the nose. There are four air channels:

• Inferior nasal meatus (underneath inferior nasal concha)
• Middle nasal meatus (underneath medial nasal concha)
• Superior nasal meatus (underneath superior nasal concha)
• Spheno-ethmoidal recess (between superior nasal concha and nasal roof)

The superior and middle nasal concha are formed from the ethmoidal labyrinths of the ethmoid bone. The ethmoidal labyrinths lie on either side of the central cribriform plate, and consist of two sheets of bone (medial and lateral). The superior and middle nasal conchae are formed from the medial sheet of bone.

The inferior nasal concha on the other hand is formed from the maxillae bones of the facial skeleton. Thus, the inferior nasal conchae is considered a facial bone, whereas the middle and superior nasal conchae are considered cranial bones.

Learn more about the anatomy of the skull in this tutorial.