<prompt> At 30 days intra uterine lifeHeart starts beatingCerebellum developsOptical vesicle appearsPinna appears  <response>: D Pinna appears Development of External Ear: Auricle, or pinna, is formed from about six mesodermal thickenings called tubercles or hillocks that appear on the Mandibular First Hyoid Second arches, around the opening of the dorsal part of the first ectodermal cleft i.e. around the opening of the external acoustic meatus. External acoustic meatus is derived from the dorsal part of the first ectodermal cleft. Mandibular arch forms only tragus a small area around it, rest of the auricle being formed from the Hyoid arch. 