3D Embryology of Ear Part 1: Internal Ear - Semicircular Canals - Utricle, Saccule and Cochlea

In this visual medical lecture, Dr. Aizaz from MedicoVisual talks about development of Ear with special emphasis on the embryology of internal ear including cochlea, vestibule, semicircular canals, utricle, saccule.

Development of inner ear starts with the thickening of surface ectoderm at the level of hindbrain that is called Otic placode. It then invaginates inwards into the underlying Mesenchyme and loses its connection with the surface ectoderm to form the auditory vesicle. This vesicle then divides into ventral and dorsal parts. A snake like extension arises from the ventral swelling that twists like a snail to form the cochlea and the remaining part of the swelling forms the saccule.
From the dorsal swelling two flat discs arise. Their central portions become apposed and is ultimately destroyed to form two canals called semicircular canals. Later, horizontal semicircular canal also forms through the similar process. The remaining part forms utricle. An extension of the utricle forms the endolymphatic duct. A condensation of Mesenchyme forms the spiral ganglia and vestibular ganglia. This condensation is hypothesized to have arisen from the medial wall of the auditory vesicle.