Development of the chick's auditory ossicle, the columella.

The avian middle ear contains a single auditory ossicle that is composed of a bony columella and a cartilaginous extracolumella. The columellar footplate (clipeolus) inserts into the oval window at its proximal end. The extracolumella attaches to the tympanic membrane at its distal end. The present study was undertaken to determine the patterns of growth, chondrification, and ossification of the chick's auditory ossicle before and after hatching.