Semicircular canal
A semicircular canal or a semicircular duct is one of three semicircular, interconnected tubes located inside each ear. The three canals are:
the horizontal semicircular canal (also known as the lateral semicircular canal),
superior semicircular canal (also known as the anterior semicircular canal),
and the posterior semicircular canal (also known as the inferior semicircular canal).
Structure
The anterior and posterior semicircular ducts are oriented vertically at right angles to each other. The lateral semicircular duct is about 30-degree angle from the horizontal plane. The orientations of the ducts cause a different duct to be stimulated by rotation of the head in different planes. Thus, the horizontal canal detects angular acceleration of the head (such as when you spin in a rotating chair), while the superior and posterior canals detect vertical head movements (such as when you bend forward to pick something up from the floor).
The semicircular canals are a component of the bony labyrinth. Among species of mammals, the size of the semicircular canals is correlated with their type of locomotion. Specifically, species that are agile and have fast, jerky locomotion have larger canals relative to their body size than those that move more cautiously.
