EAC develops from 1st cleft and EAM develops from 1st arch?
The development of the external auditory canal (EAC) and external acoustic meatus (EAM) involves contributions from both the first pharyngeal cleft and the first pharyngeal arch.
During embryonic development, the first pharyngeal cleft gives rise to the external auditory canal. This cleft is located between the first and second pharyngeal arches. The first pharyngeal cleft forms a groove that deepens and eventually develops into the EAC, which is the passageway that leads from the external ear to the middle ear.
On the other hand, the first pharyngeal arch gives rise to various structures, including the mandible (lower jaw) and certain parts of the middle ear. The EAM, which is the outer portion of the ear canal, is formed by the fusion of tissues derived from both the first pharyngeal cleft and the first pharyngeal arch.
So, to summarize, the development of the EAC involves contributions from the first pharyngeal cleft, while the development of the EAM involves contributions from both the first pharyngeal cleft and the first pharyngeal arch.