Computed tomogram showing normal maxillary sinus. The anterior portion of the maxillary sinus (MS) drains through the maxillary ostium into the ethmoid infundibulum (open arrow), which is bounded superolaterally by the ethmoid bulla (EB) and inferomedially by the uncinate process (UP). The ethmoid infundibulum opens through the hiatus semilunaris, which is a two dimensional slitlike opening that connects the infundibulum with the middle meatus (short, white arrow). The infraorbital foramen (IOF), inferior turbinate (IT), and inferior meatus (IM) are also shown. Reproduced from Shankar et al30 with permission