Acoustic meatus

Acoustic Meatus is a term used in anatomy to refer to certain canals within the human ear. There are two types of acoustic meatus: the external acoustic meatus and the internal acoustic meatus.

External Acoustic Meatus

The External Acoustic Meatus (EAM), also known as the external auditory canal or ear canal, is a tube running from the outer ear to the middle ear. The human EAM extends from the pinna to the eardrum and is approximately 2.5 cm in length and 0.7 cm in diameter.

The EAM is divided into two parts. The outer third, cartilaginous part, is surrounded by cartilage while the inner two-thirds, bony part, is surrounded by bone. The skin of the EAM contains hairs and glands that produce cerumen, or earwax.

Internal Acoustic Meatus

The Internal Acoustic Meatus (IAM) is a canal within the petrous part of the temporal bone of the skull. It is approximately 1 cm in length and serves as a passage for nerves and vessels that supply the ear.

The IAM carries two important nerves: the facial nerve (VII) and the vestibulocochlear nerve (VIII). The facial nerve is involved in facial expressions and taste, while the vestibulocochlear nerve is involved in hearing and balance.

Clinical Significance

Abnormalities or damage to the acoustic meatus can lead to a variety of health problems. For instance, blockage of the EAM by earwax can cause temporary hearing loss. Infections of the EAM, known as otitis externa, can cause pain and discharge. Tumors can also develop in the IAM, often leading to symptoms such as hearing loss, tinnitus, and dizziness.

See Also

• Ear
• Human ear
• Otitis externa
• Tinnitus
• Vestibulocochlear nerve