Semicircular Ducts:

There are present three semicircular ducts; the anterior, the posterior and the lateral semicircular ducts. They arise from the utricle. The anterior and posterior semicircular ducts arise from crus commune.

Each semicircular duct is enlarged at one end to give rise to a small rounded ampulla. The anterior and lateral semicircular ducts bear ampullae at their anterior ends, while the posterior duct contains an ampulla at its posterior end.

Each ampulla contains a sensory patch of cells, the crista Each crista consists of two kinds of cells, the sensory and supporting cells. The sensory cells bear long sensory hairs at their free ends and nerve fibres at the other end. The sensory hairs are partly embedded in a gelatinous mass, the cupula. The cristae are concerned with balance of the body.