Identify the structure (Arrow) shown in the Photograph
A. Internal Auditory canal.
B. Auditory tube.
C. Facial Nerve.
D. Vestibulocochlear Nerve.
Ans : B. Auditory tube
- Also known as the Eustachian tube or pharyngotympanic tube.
- It is a tube that links the nasopharynx to the middle ear. It is a part of the middle ear.
36 mm long in adults.
- Directed anteriorly, inferiorly & medially from anterior wall of M.E., forming angle of 45 degree with horizontal
- Eustachian tube opens into middle ear cavity at Medial wall
- Enters naso-pharynx 1.25 cm behind posterior end of inferior turbinate.
- Two parts – Postero lateral bony part (12mm) and Antero medial fibro cartilaginous part (24mm).
- Junction b/w 2 parts is isthmus, narrowest part of Eustachian Tube.
- Ostmann’s pad of fat- helps the tube closed at pharyngeal end
- Lined by pseudo stratified ciliated columnar, cilia beat in the direction of nasopharynx.
- Normally Eustachian tube (ET) is closed and opens intermittently during yawning, swallowing and sneezing through contraction of Tensor vili palatini and Levator veli palatini muscle.
- Ventilation & regulation of middle ear pressure
- Protection against nasopharyngeal sound pressure and reflux of nasopharyngeal secretions
- Clearance of middle ear secretions