<prompt> In functional endoscopic sinus surgery FESS opening is made through?Sphenoethmoidal recessOsteomeatal complexInferior turbinateMiddle turbinate  <response>: Ans. isbi.e., Osteomeatal complexRef HeaddNeckSurgery -otolnryryologlt,Vol. l byByronl.Bailey,lonasT.Ionson,ShawnD. Newlands4hep. 459; Textbook Of Oral and maxillofacial Surgery full colour leByNeelimaAniL 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. 