<prompt> Distance of promontory from tympanic membrane:2 mm5 mm6 mm7 mm  <response>: Ans. A 2 mm Ref. Dhingra 6thed p450; point 129When seen in coronal section, the cavity of the middle ear is biconcave, as the medial and lateral walls are closest to each other in the center.The distances separating them are: Near the roof 6 mm Epitympanum AtticIn the centre 2 mm MesotympanumNear the floor 4 mm HypotympanumThe medial wall of the tympanic cavity is formed by the labyrinth and the lateral wall is formed by the tympanic membrane. 