Distance of promontory from tympanic membrane:

Ans. A 2 mm Ref. Dhingra 6th/ed p450; point 129"When 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 (Attic)In 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.