The tubotympanic recess of the first pharyngeal pouch grows rapidly and comes into the contact with the floor of the first pharyngeal cleft. Its distal portion widens and gives rise to the primitive tympanic cavity, while the proximal, unexpanded portion becomes the auditory tube.
The auditory ossicles (malleus, incus and stapes) develop by endochondral ossification of the cartilage of the first two pairs of the pharyngeal arches. Later in the development, the surrounding mesenchyme dissolves. The endodermal epithelial lining extends along the wall of the newly formed space and coats the bony ossicles.