Eustachian tube
From Wikipedia, the free encyclopedia
| Eustachian tube | |
|---|---|
 |
|
| Anatomy of the human ear. | |
| The middle ear | |
| Latin | tuba auditiva |
| Gray's | subject #230 1042 |
| Precursor | first pharyngeal pouch |
| MeSH | Eustachian+tube |
| Dorlands/Elsevier | t_21/12826987 |
The Eustachian tube (or auditory tube) is a tube that links the pharynx to the middle ear. In adults the Eustachian tube is approximately 35 mm long. It is named after the 16th century anatomist Eustachius.[1] Some modern medical books call this the pharyngotympanic tube.[2]
Contents |
[edit] Location
The Eustachian tube extends from the anterior wall of the middle ear to the lateral wall of the nasopharynx, approximately at the level of the inferior nasal concha. A portion of the tube (~1/3) proximal to the middle ear is comprised of bone; the rest is composed of cartilage [3] and raises a tubal elevation, the torus tubarius, in the middle ear where it opens.
[edit] Functions
[edit] Pressure equalization
Normally the Eustachian tube is closed, but it can open to let a small amount of air through to equalize the pressure between the middle ear and the atmosphere. When this happens we hear a small pop, an event familiar to aircraft passengers or drivers in mountainous regions. Yawning or swallowing can pull on muscles in the neck, causing the tube to open. Some people are born with the ability to contract just these muscles voluntarily, similar to people who can wiggle their ears. Doing so will make one's voice sound deeper to one's self. Without this airway, the middle ear would be isolated from the atmosphere, and could be easily damaged by pressure changes.
[edit] Mucus drainage
The Eustachian tube also drains mucus from the middle ear. Upper airway infections or allergies can cause the Eustachian tube to become swollen, trapping bacteria and causing ear infections. This swelling can be reduced through the use of pseudoephedrine. Earaches are more common in children because the tube is more horizontal, making the movement of fluid harder.
An alternative method of relieving the pain felt by an earache is to have a physician or chiropractor perform endonasal therapy, which is a useful form of local treatment for catarrh problems. Endonasal therapy is a basic treatment used to initiate the draining and cleansing processes necessary to remove congestion in the Eustachian tubes.
[edit] Embryologic development
The Eustachian tube is derived from the first pharyngeal pouch, which during embryogenesis forms a recess called the tubotympanic sulcus. The sulcus deepens to meet the first pharyngeal cleft forming the tympanic membrane. The distal part of the tubotympanic sulcus gives rise to the tympanic cavity, while the proximal tubular structure becomes the Eustachian tube.
[edit] Muscles
There are four muscles associated with the function of the Eustachian tube:
- levator veli palatini (innervated by the vagus nerve)
- salpingopharyngeus (innervated by the vagus nerve)
- tensor tympani (innervated by the mandibular nerve of CN V)
- tensor veli palatini (innervated by the mandibular nerve of CN V)
[edit] Additional images
 External and middle ear, opened from the front. Right side. |
 Horizontal section through left ear; upper half of section. |
 View of the inner wall of the tympanum (enlarged.) |
 The right membrana tympani with the hammer and the chorda tympani, viewed from within, from behind, and from above. |
[edit] References
- ^ synd/1463 at Who Named It
- ^ Dictionary at eMedicine pharyngotympanic+%28auditory%29+tube
- ^ University of Michigan
