From which embryonic layer does the outer ear form?

The outer ear develops primarily from the ectoderm, which is one of the three primary embryonic layers. The ectoderm is responsible for forming structures of the outer body, including the skin and its appendages, which encompasses the external portion of the ear. During embryonic development, the ectoderm contributes to the formation of the auricle (pinna) and the external auditory canal.

The mesoderm is involved in the development of internal structures, such as muscles and bones, and the endoderm mainly forms the internal linings of the body, including organs like the gastrointestinal tract and respiratory system. Therefore, the outer ear specifically originates from the ectoderm, making it the correct answer.