... esophagus¹

The muscle of the upper third of the esophagus is skeletal type muscle similar to the pharynx. The muscle of the lower two thirds of the esophagus is smooth like the muscle of the stomach, small and large intestines.

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... bolus.²

The signal for the contraction probably comes from the swallowing center in the brain stem and is then propagated with the aid of the nerves in the esophagus

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... sphincter.³

`Chalasia' affects infants; they have to be kept upright following feeding

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... pseudo-achalasia.⁴

Of interest, the manometric and radiological appearances of achalasia can be induced in the cat by application of a constricting band around the lower esophagus. If the constriction is removed in a short period of time the esophagus returns to normal. However, if the constriction is removed too late, the achalasia is permanent.

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