Which of the following is true upper esophageal sphincter?
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
Its physiological not anatomical
It has pressure of 10 to 20 mmHg
It is under hormonal control
It is formed by striated muscles
G.I.T