Muscle tone in the lower oesophagus is

A. True The high-pressure zone indicates the ‘cardiac sphincter’.

B. True It prevents reflux of acid into the oesophagus.

C. False It is decreased and heartburn is common in pregnancy.

D. True This prevents reflux during gastric contractions.

E. False These reduce tone, suggesting that cholinergic nerves have a role in maintaining normal tone.