The auditory tube (also known as pharyngotympanic tube, Eustachian tube, latin: tuba auditiva) is a tunnel that connects the tympanic cavity to the nasopharynx and equalizes pressure on both sides of the tympanic membrane.
The opening of the auditory tube in the middle ear is located in its anterior wall, and from here the auditory tube extends forward, medially, and downward to enter the nasopharynx, opening in the lateral wall of the nasopharynx just posterior to the inferior meatus of the nasal cavity.
The main functions of the auditory tube are as following:
- pressure equalization on both aspects of the tympanic membrane;
- mucociliary clearance and `drainage`;
- protection from the influences of the nasopharyngeal environment and loud sounds.
The auditory tube consists of two parts:
- bony part (the one-third nearest the middle ear);
- a cartilaginous part (the remaining two-thirds).
The opening of the bony part of the auditory tube is clearly visible on the inferior surface of the skull at the junction between the squamous and petrous parts of the temporal bone, immediately posterior to the foramen ovale and foramen spinosum.
The blood supply to the auditory tube is provided by the following arteries:
- ascending pharyngeal artery(a branch of the external carotid artery);
- middle meningeal artery (a branch of the maxillary artery);
- artery of the pterygoid canal (a branch of the maxillary artery).
The venous blood is drained from the auditory tube via the pterygoid plexus of veins in the infratemporal fossa.
The nerve supply to the auditory tube is provided by the tympanic plexus.