[1] When the head changes position, the endolymph in the ducts lags behind due to inertia and this acts on the cupula which bends the cilia of the hair cells.

Specifically, species that are agile and have fast, jerky locomotion have larger canals relative to their body size than those that move more cautiously.

It measures from 12 to 15 mm (0.47 to 0.59 in), and its arch is directed horizontally backward and laterally; thus each semicircular canal stands at right angles to the other two.

It is 15 to 20 mm (0.59 to 0.79 in) in length, is vertical in direction, and is placed transversely to the long axis of the petrous part of the temporal bone, on the anterior surface of which its arch forms a round projection.

The posterior semicircular canal is part of the bony labyrinth and its duct is used by the vestibular system to detect rotations of the head in the coronal plane.

Findings from a 2009 study demonstrated a critical late role for bone morphogenetic protein 2 (BMP-2) in the morphogenesis of semicircular canals in the zebrafish inner ear.

It is suspected that the role of BMP-2 in semicircular canal duct outgrowth is likely to be conserved between different vertebrate species.

The base of each duct is enlarged, opening into the utricle, and has a dilated sac at one end called the membranous ampulla.

Within approximately 10 seconds of achieving constant motion, the endolymph catches up with the movement of the duct and the cupula is no longer affected, stopping the sensation of acceleration.

If the pilot were to sustain a constant rate turn, the endolymph would eventually catch up with the ducts and cease to deflect the cupula.

As the endolymph stabilizes, the semicircular ducts stop registering the gradual turn and the aircraft slowly loses altitude until impact with the ground.

[7] This article incorporates text in the public domain from page 1049 of the 20th edition of Gray's Anatomy (1918)