Anatomy Of External Auditory Canal

The adult external auditory canal measures about 2.5 cms. This measurement refers to the length of the canal, which is the passage that leads from the outer ear to the middle ear. It is important for the canal to have an appropriate length to ensure the proper transmission of sound waves. If the canal is too short or too long, it can affect the way sound is conducted and perceived by the individual. Therefore, a length of 2.5 cms is considered to be within the normal range for an adult's external auditory canal.

The external auditory canal develops from the first branchial cleft. During embryonic development, the first branchial cleft forms a groove that deepens and eventually becomes the external auditory canal. This canal connects the outer ear to the middle ear and allows sound waves to travel into the ear. The first branchial cleft also gives rise to other structures in the head and neck region, such as the external ear and certain parts of the face.

The statement is true because the narrowest portion of the external canal is indeed at its bony cartilaginous junction. This junction is where the bony part of the ear canal meets the cartilaginous part, and it is the narrowest point in the entire external canal. This narrowness helps to protect the ear from foreign objects and restricts the entry of large objects into the ear canal.

Foramen Huschke is seen in the antero inferior portion of the bony external auditory canal. This is a small opening that can be found in the front and lower part of the canal. It is named after Johann Friedrich Huschke, a German anatomist who first described it. The foramen Huschke is important because it can potentially lead to complications such as cholesteatoma, a type of abnormal skin growth in the middle ear.

The external auditory canal is fully canalized by the 28th week of gestation. This means that by this time, the auditory canal has formed and is open, allowing sound waves to enter the ear. The development of the auditory canal is a gradual process that occurs during fetal development, starting around the third week of gestation. By the 28th week, the canal is fully formed and ready to function.

The embryological primary meatus corresponds to the lateral third of the external auditory canal. This means that during embryonic development, the external auditory canal is formed from the lateral third of the primary meatus. The primary meatus is a groove-like structure that develops in the embryo and eventually gives rise to the external auditory canal. Therefore, the correct answer is the lateral third of the external auditory canal.

The external auditory canal is the only skin lined culdesac in the entire human body. It performs both auditory and non-auditory functions, such as protecting the middle and inner ear from foreign objects and regulating pressure. Additionally, the canal is self-cleansing in nature, as it produces cerumen (earwax) to trap dust and debris and moves it out of the ear.

The external auditory canal is divided into two portions, with the outer two-thirds being cartilaginous and the inner one-third being bony. The antero-inferior wall of the canal is slightly longer than the postero-superior wall. Additionally, the bony canal is directed antero-inferiorly.

The features of the infant external auditory canal include the fact that at birth, the tympanic membrane and ossicles are of adult size. Additionally, the tympanic membrane and squamous portion of the temporal bone form the roof of the external canal. Furthermore, the shape of the external canal in a neonate is nearly straight.