Otic vesicle chick, invagination of the otic placode occurs passively due to the movements of the surrounding placode. The otic placode in zebrafish, on the other hand, occurs by cavitation; the ectodermal placode condenses and forms an ovoid ball directly below the embryo surface. Otic vesicle formation occurs later, during the 25-30 somite stage in mice. Otic vesicle Otic vesicle, or auditory vesicle, consists of either of the two sac-like invaginations formed and subsequently closed off during embryonic development. It is part of the neural ectoderm, which will develop into the membranous labyrinth of the inner ear. This labyrinth is a continuous
Supernumerary body part Supernumerary body part Supernumerary body parts are most commonly a congenital disorder involving the growth of an additional part of the body and a deviation from the body plan. Body parts may be easily visible or hidden away, such as internal organs. Many additional body parts form by the same process as conjoined twins: the zygote begins to split but fails to completely separate. This condition may also be a symptom of repeated occurrences of continuous inbreeding in a genetic line. Specific types of additional body parts include: Vestigial structures are anatomical structures of organisms in a species which are