Anatomy and Function of Semicircular Canals in the Ear

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The semicircular canals are three tiny tubes located in the inner ear. Their primary job is to regulate balance and sense head position.

The three semicircular canals—the anterior, lateral, and posterior—are filled with fluid that remains in position as you move your head. Each one provides specific information about body position and balance. They help to ensure that your vision remains stable despite motion and activity.

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Anatomy

The semicircular canals are part of your body's vestibular system, which helps you maintain your balance and sense your body's position. Each semicircular canal has a specific structure, although it's possible to have certain anatomical variations.

Structure

There are three round, hollow, semicircular canals. Inside each of these tubes is a fluid called endolymph. This fluid stimulates hair cells inside a cluster of nerves called the crista ampullaris.

Each semicircular canal starts and ends in the vestibule, a cavity in the inner ear. Each one is angled on a specific plane. While their lengths vary slightly, each forms a loop with a diameter of 1 millimeter. Here’s a breakdown:

  • The anterior semicircular canal, also called the “superior” canal, is vertically positioned in a manner dividing the right and left parts of the body.
  • The lateral semicircular canal is the shortest of the three and is angled at about 30 degrees to the horizontal plane, which is why it’s sometimes called the “horizontal” canal.
  • The posterior semicircular canal is oriented on the frontal plane, which vertically divides the front and back sides of the body. It’s also known as the “inferior” semicircular canal.

Ampullae are widened areas at the end of each semicircular canal that contain structures associated with sensations of balance.

Anatomical Variations

As with other parts of the inner ear, the semicircular canals can experience congenital deformations. Three malformations most commonly affect these structures:

  • Semicircular canal dysplasia: This is an inherited under-development of these structures. This occurs in about 40% of those who experience malformation of the cochlea. This condition is associated with the conditions Down syndrome, CHARGE syndrome, and Goldenhar syndrome.
  • Semicircular canal aplasia: This is characterized by a complete absence of the posterior semicircular canal, which occurs in certain congenital conditions affecting the cochlea and vestibule. This is typically accompanied by severe hearing loss.   
  • Semicircular canal dehiscence: The walls of any of the three semicircular canals may become thinned or weakened. This can create a “third window” into the inner ear, causing possible auditory symptoms, including the Tullio phenomenon, in which loud noises cause vertigo and uncontrolled eye movements. Others may have longstanding dizziness.

Location

The semicircular canals are located in special semicircular ducts in the bony labyrinth of each inner ear. These ducts are located in the temporal bones, paired bones at the sides and base of the skull.

They hang above the vestibule and the cochlea, the snail shell-shaped organ connected to it. The canals have nerves running to the vestibular ganglion (a bundle of nerves), eventually reaching receptors in the upper spinal cord.

Function

The semicircular canals are primarily associated with sensing the rotational position of the head. Due to inertia, fluid movement lags behind head movements. This stimulates the hair cells and provides signals to the brain that are crucial for regulating body position and maintaining stability.

The activity of the canals is complementary—head movements cause increased signaling on one side of the head while simultaneously inhibiting those from its counterpart on the other.

This allows for smooth eye motion, resulting in stable vision despite head turns or twists. This is why you sense your head nodding or tilting and don't perceive everything you see as tipping over.

The semicircular canals work alongside the otolithic organs. Together, they're essential for proprioception (the sense of the body in space and while moving) and balance.

This information is sent to vestibular nuclei in the brain stem, which relay this information to other parts of the brain associated with movement and coordination.

Conditions Associated With the Semicircular Canals

Disorders or problems with the semicircular canals can affect your balance and vision. These conditions may include:

  • Motion sickness: This prevalent condition, in which you feel sick or nauseous while in a car, boat, or other vehicle, can result from activity in the semicircular canals. Among other causes, it can result from diseases or disorders impacting the inner ear.
  • Benign paroxysmal positional vertigo (BPPV): This condition causes very short-lived vertigo, defined as dizziness and an inability to maintain balance whenever one moves one's head. It also causes nausea and vomiting.
  • Ménière's disease: This disease is characterized by vertigo, tinnitus (ringing in the ears), and fluctuating hearing loss. It is caused by a build-up of fluid within the inner ear, impacting the semicircular canals.  
  • Nystagmus: This is when your eyes make uncontrolled, rapid, and jerky movements. It is a physical manifestation of a vestibular disorder, not a condition in and of itself.

Diagnostic Tests

Tests of your vestibular system (including the semicircular canals) evaluate oculomotor function, balance, and proprioception. Three tests are typically performed in the clinical setting:

  • Caloric reflex test: To examine the vestibulo-ocular reflex, this test involves squirting a syringe of water into the ear. Differences between the water temperature and the endolymph create an electrical current, which spurs rapid eye movements. This test can determine if there is damage to certain portions of the brain.
  • Head impulse test: In cases of sudden onset vertigo, the function of the semicircular canals can be tested by applying electrical signals to the sides of the head while tracking eye and head movements. By measuring reactions to these stimuli, doctors can isolate the causes of the condition.
  • Video head impulse test (vHIT): The vHIT can be used to determine the cause of vertigo. In the test, patients wear special goggles and are asked to look straight ahead as impulses are delivered, testing each semicircular canal plane. 

Summary

The semicircular canals are three small tubes in your inner ear. As part of the vestibular system, they help regulate balance in your body. Each semicircular canal has a fluid called endolymph that stimulates hair cells in the tubes. This sends signals to the brain that help sense your position and maintain stability.

Disorders in the semicircular canals can cause conditions like motion sickness, vertigo, and nystagmus. Your healthcare provider can conduct tests of the vestibular system to evaluate function and balance.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Radiopaedia. Semicircular canals.

  2. Kenhub. Vestibular system.

  3. Radiopaedia. Semicircular canal dysplasia.

  4. Michel G, Espitalier F, Delemazure AS, Bordure P. Isolated lateral semicircular canal aplasia: Functional consequencesEuropean Annals of Otorhinolaryngology, Head and Neck Diseases. 2016;133(3):199-201. doi:10.1016/j.anorl.2015.09.002

  5. Radiopaedia. Semicircular canal dehiscence.

  6. Rabbitt R. Semicircular canal biomechanics in health and disease. J Neurophysiol. 2019;121(3):732-755. doi:10.1152/jn.00708.2018

  7. Neuroscience Online. Vestibular system: structure and function.

  8. MedlinePlus. Motion sickness.

  9.  Cedars-Sinai Hospital. Benign paroxysmal positional vertigo.

  10. National Institute on Deafness and other Communication Disorders. What is Ménière's disease? Diagnosis and treatment.

  11. MedlinePlus. Nystagmus.

  12. Califano L, Iannella R, Mazzone S, Salafia F, Melillo MG. The video head impulse test in the acute stage of posterior canal benign paroxysmal positional vertigo. Acta Otorhinolaryngol Ital. 2021;41(1):69-76. doi:10.14639/0392-100X-N1033

  13. Hougaard D, Abrahamsen E. Functional testing of all six semicircular canals with video head impulse test systems. J Vis Exp. 2019;(146). doi:10.3791/59012

Mark Gurarie Mark Gurarie

By Mark Gurarie
Gurarie is a writer and editor. He is a writing composition adjunct lecturer at George Washington University.