<prompt> Sphenoid sinus drains into which of the followingSpheno-ethmoidal recessMiddle meatusSuperior meatusHiatus semilunaris  <response>: The right and left sphenoidal air sinuses lie within the body of sphenoid bone. They are separated by a septum. The two sinuses are usually unequal in size Each sinus opens into the sphenomandibular recess of corresponding half of the nasal cavity. Ref BDC volme3,6th edition pg 246 