Auditory tube

At a glance

English

Auditory tube

Latin (TA2)

Tuba auditiva

System

Nerve

Region

Head

Side

Paired, left and right

About the auditory tube

The auditory tube, also called the Eustachian or pharyngotympanic tube, connects the tympanic cavity of the middle ear with the upper part of the throat behind the nose. Its two main tasks are to let air in and out of the middle ear and to drain mucus from it.

The tube has two parts that meet at a slight angle. The back third, nearest the ear, is a bony canal about 12 mm long in the petrous temporal bone. It opens from the front of the middle ear cavity, under the small canal that houses tensor tympani, and narrows as it runs forward to end at the angle between the squamous and petrous parts of the bone, where its rough rim anchors the cartilage. The front two-thirds, about 24 mm, is formed by a triangular plate of elastic cartilage whose upper edge is rolled over like a hook, the gap below being closed by fibrous membrane. This part sits in a furrow where the petrous bone meets the sphenoid's greater wing. Its wide end raises a bump, the torus tubarius, behind the pharyngeal opening in the side wall of the nasopharynx, about level with the inferior concha. Its lining is ciliated columnar epithelium, thin in the bony part and rich in mucous glands in the cartilaginous part, with lymphoid tissue, the tubal tonsil, near the pharyngeal opening.

At rest the cartilaginous part is closed. Swallowing and yawning open it, mainly through tensor veli palatini, helped by levator veli palatini and salpingopharyngeus, so a little air passes and middle ear pressure matches the outside air. A blocked tube on a descending aircraft or during a dive leaves the drum pulled in, giving pain and dull hearing until swallowing or a Valsalva manoeuvre opens it, and a large pressure difference can injure the ear.

In young children the tube is shorter, wider and more horizontal, which is one reason middle ear infections are common at that age. Colds, allergy, enlarged adenoids, sinus disease and smoking can block it, trapping fluid behind the drum (glue ear) and reducing hearing. A tube that stays open, a patulous tube, instead lets people hear their own voice and breathing too loudly.

Course and supply

Arises from

Begins at its tympanic opening, in the front wall of the middle ear cavity.

Ends in

Ends at its pharyngeal opening on the side wall of the nasopharynx, behind the inferior nasal concha, framed by the torus tubarius.

Supplies

Keeps middle ear air pressure equal to that outside, and drains secretions from the middle ear to the nasopharynx.

Nerve supply

Sensation from the tympanic plexus of the glossopharyngeal nerve, with a contribution from the pharyngeal branch of the pterygopalatine ganglion (maxillary nerve) near the pharyngeal end.

Blood supply

The ascending pharyngeal artery, the artery of the pterygoid canal and branches of the middle meningeal artery; veins drain to the pharyngeal and pterygoid plexuses.