Where is Auditory Tube Located and Whats is its Function?
Auditory tube /pharyngotympanic/Eustachian tube is a trumpet-shaped tube which connects middle ear with nasopharynx.
- Is 3.5-4cm. long.
- Is directed downwards, forwards and medially.
- It balances the air pressure in the middle ear with the atmospheric pressure, thus allowing free movement of tympanic membrane.
Name the Parts of Auditory Tube.
Auditory tube is divided into two parts:
- Cartilaginous part– it forms anterior 2/3rd. it lies in sulcus tubae (formed by articulation of petrous part of temporal bone with greater wing or sphenoid). It opens into the lateral wall of naopharynx by passing through the gap between the base of skull and superior constrictor of pharynx.
- Bony part – forms posterior 1/3rd , it lies in petrous part of temporal part and extends from the tympanic cavity to the sulcus tubae.
Muscles attached to the cartilaginous part of auditory tube are tensor tympani, levator palatini , tensor palatini and salpingopharyngeus. Tensor tympani, levator palatini help in opening the auditory tube.
Describe the Nerve Supply of Auditory Tube.
- Lateral part of the tube is supplied by glossopharyngeal nerve via tympanic plexus.
- Medial part is supplied by pharyngeal branch of pterygopalatine ganglion .
Applied Aspect
Infection can spread from the nasopharynx to the middle ear through the auditory tube.
In infants the auditory tube is shorter and is less oblique as compared to adults and therefore it is easier for the infections to spread from the nasopharynx to the middle ear cavity.
Infections in nasopharynx can cause blockage of auditory tube, which leads to decreased pressure in middle ear and the tympanic membrane is pulled medially. This results in difficulty in hearing.