Which of the following is true upper esophageal sphincter?
Its physiological not anatomical
It has pressure of 10 to 20 mmHg
It is under hormonal control
It is formed by striated muscles
Upper oesophageal sphincter(UES) is a true sphincter. It has pressure of 35-200mmHg. It is formed by cricopharyngeal muscle which is a striated muscle. It is under Neurochemical control.The only neurotransmitter of UES opening or closing muscles found to mediate contraction is acetylcholine acting through nicotinic cholinergic receptors. Ref: Medical Physiology, Indu Khurana
G.I.T