The ear is a fascinating and complex appendage and organ. Formation is from structures called branchial arches. Branchial (from Greek branchia gills) arches are composed of endoderm on the internal aspect, by clefts composed of ectoderm on the external side with the central mesoderm containing the muscle, cartilage, vessels and nerves that will ultimately supply and establish the surrounding anatomic structures. Molecular signaling from the ectoderm leads the mesenchyme from the mesodermal (central) layer to eventually, if it works out as planned, to obliterate the clefts and and pouches. If clefts persist, they are given names, such as Type I branchial cleft cyst. When this signaling goes wrong, there are different degrees of anomalies, from absence of specific auricle components to microtia or even anotia if there is complete failure.
The ear begins to form the otic placode and vestibulocochlear ganglia at 3 weeks of gestation. The external canal then develops from the first branchial cleft at 4 weeks. By 28 weeks there is a fully open external canal. Failure to canalize can result in membranous or bony stenosis or atresia (from Latin a = no and Greek trēsisperforation, from tetrainein to pierce). Development of the auricle (external ear) begins at 5 weeks gestation with development of the auricular hillocks numbered from 1 through 6, derived from the first (mandibular) and second (hyoid) branchial arches. So the inner ear has already formed when the external ear begins.
The ear develops in a predictable manner, with various alterations in development resulting in predictable deformities when the process is interrupted. Knowledge of auricular development as well as normal external anatomy allows for precise evaluation of the ear and assists in selecting appropriate reconstructive techniques to optimize the complex 3-dimensional anatomical outcomes.
If you have a ear question, please do not hesitate to call me for an appointment. Office number is 989-839-6201, fax is 989-839-6202. Providers can page me through the Midland hospital operator. Patients can reach me by way of the patient portal.
Let me know how I can be of help to you.
Philip Harris, MD FARS
Ear Nose Throat and Cancer of the Head and Neck
Serving Gladwin, Clare, Midland and Alpena
Call for appointment and ask to see Dr. Harris