Eustachian Tube - Structure and Functions

The human ear is the vital organ of hearing as well as equilibrium. It perceives and analyses sound waves by a mechanism that converts sound into electrochemical impulses – transduction. There are several structures in the human ear that help in this hearing mechanism and equilibrium. Let’s have a look at one such ear structure – the Eustachian tube.

Table of Content:

What is the Eustachian Tube?

The structure of the human ear comprises three sections, namely – the outer ear, the middle ear and the inner ear. Here, the anatomy of the middle ear shows the presence of the Eustachian tube.

The middle ear is an air-filled space connected to the back of the nose by a long, thin tube called the Eustachian tube. Thus it serves as a connection between the pharynx and the middle ear. The main function of the eustachian tube is to equalise pressure between the middle ear and the atmosphere outside.

Eustachian Tube – Structure

The terms auditory tube and pharyngotympanic tube are often synonymous with the Eustachian tube. This tube is approximately 3 mm in diameter and 35 mm long in adults. In that, about one-third structure near the middle ear is made of bone. The remaining two-third structure forms the cartilaginous part. Furthermore, the structure is lined with mucous membranes.

The upper end of the Eustachian tube is bony and narrow. It becomes cartilaginous and wider as it nears the pharynx. Thus the tube is mainly considered as a fibrocartilaginous structure connecting the nose and the air cell system of the temporal bone.

Totally four muscles contribute to the closing and opening of the Eustachian tube. These muscles are located near the jaw, soft palate, ear, neck and head. Also, these muscles are innervated by the cranial nerves.

Functions of Eustachian Tube

The major physiological functions of the Eustachian tube related to the air cell system (mastoid cells) and middle ear are –

  • Ventilation or pressure regulation
  • Clearance or mucus drainage
  • Protection

Pressure regulation

The Eustachian tube regulates gas pressure and atmospheric pressure between the middle ear and the nasopharynx. The tube mostly remains closed, but it opens while chewing, swallowing, yawning, etc. These activities are considered ear clearing methods as the air passes through the tube between the middle ear and nasopharynx, and thus, the air pressure is regulated.

Clearance

The Eustachian tube also drains the mucus of the middle ear into the nasopharynx. This is called mucociliary clearance. This is because small hair-like cilia cover the tube to aid in the drainage of middle ear secretions to the pharynx.

Protection

The tube also protects from viruses and bacteria. It stays closed and serves as a protective barrier for the middle ear. During allergies, nasal congestion and URTI (upper respiratory tract infection), the opening membrane of the tube gets swollen and causes trapping of fluid, which eventually leads to clogging. This further leads to bacterial growth and can result in ear infections.

Also, Check: What is the function of Cochlea?

Eustachian Tube Dysfunction

The abnormal functioning of the Eustachian tube is termed as Eustachian tube dysfunction. The diagnosis of the dysfunction can be hard as the Eustachian tube is hardly visible.

The specificity of the dysfunction varies based on the different ways in which the Eustachian tube functions abnormally. The dysfunction can be due to obstruction of the tube (too closed) or patulous tube (too open). Also, the term middle-ear disease includes the conditions related to Eustachian tube dysfunction.

Symptoms Associated with Eustachian Tube Dysfunction

Some common symptoms are:

  • Ear pain
  • Ear might feel full or plugged
  • Buzzing sound or muffled sound
  • Trouble in keeping balance

Frequently Asked Questions

Who first discovered the Eustachian tube?

The description of the Eustachian tube or auditory tube was first published in 1562 by Bartolomeus Eustachius, after whom the structure is named. He described it as an auditory passage in his thesis Epistola de auditus organis.

What are the structures present in the middle ear?

The middle ear consists of three tiny bones, namely stapes, malleus and incus. Malleus is attached to the tympanic membrane, and the stapes are attached to the oval window of the cochlea. Incus is found between the stapes and malleus. The eustachian or the auditory tube connects the middle ear and the pharynx.

What is an eardrum?

The tympanic membrane or eardrum is a thin membrane-like structure that separates the external and the middle ear. It is a part of the outer ear structure that receives and amplifies sound.

Also see: Well-labelled diagram of Ear

Keep exploring BYJU’S Biology for more exciting topics.

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