<prompt> All open into middle meatus exceptFrontal sinusSphenoid sinusMaxillary sinusEthmoidal sinus  <response>: THE FOLLOWING FEATURES ARE: 1.Ethmoidal bulla 2.Hiatus semilunaris 3.Infundibulum 4.Opening of frontal air sinus 5.Opening of anterior ethmoidal sinus 6.Opening of maxillary sinus Ref BDC volume 3,sixth edition pg 243 