In functional endoscopic sinus surgery (FESS) opening is made through?

Ans. is'b'i.e., Osteomeatal complex[Ref HeaddNeckSurgery -otolnryryologlt,Vol. l byByronl.Bailey,lonasT.Ionson,ShawnD. Newlands4h/ep. 459; Textbook Of Oral and maxillofacial Surgery (full colour) l/eByNeelimaAniL p. 583Functional endoscopic sinus surgery (FESS):FESS is minimally invasive technique in which sinus air cells and sinus ostia are opened under direct vision.It is called functional because it aims to return the working of the sinus to normal.FESS is based on the hypothesis that the osteomeatal complex (maxillary sinus ostium, anterior & middle ethmoid ostia, frontal recess, infundibulum and middle meatal complex) is a key area in the pathogenesis of chronic sinus disease.