The distance between tympanic membrane and medial wall of middle ear at centre is:: (A) 3 mm, (B) 4 mm, (C) 6 mm, (D) 2 mm
Answer is D. Middle ear cavity is shaped like a cube, compressed from side to side. In coronal section it resembles a biconcave disc. The veical and anteroposterior diameters are 15 mm each, and transverse diameters are: 6 mm (at roof), 2 mm (in the centre). 4 mm (at floor)