Oesophageal motor functions and its disorders

The function of the oesophagus is relatively straightforward—to transport the swallowed food into the stomach. In order to meet this functional need, the design of the oesophagus is simple; a relatively straight muscular tube that is guarded at it two ends by the upper and lower oesophageal sphincters. Following a voluntary act of a swallow, the two sphincters relax and open and a contraction wave or peristalsis sweeps behind the bolus autonomously. The contraction wave sweeps through the entire length of the oesophagus followed by closure of the two sphincters. Neuromuscular control mechanisms that bring about normal functioning of the two sphincters and oesophageal peristalsis are complex and require fine coordination of the muscles and nerves at the level of the central and peripheral nervous system. Disturbance of sphincters and peristalsis causes symptoms of dysphagia and oesophageal pain. The latter may manifest either as chest pain (pressure-like sensation) or heartburn (retrosternal burning). The nature of dysfunction in oesophageal motor disorders has been the subject of intense investigation for several decades. In this paper, we will review briefly the physiology of oesophageal peristalsis and lower oesophageal sphincter and then attempt to understand what may be wrong in motor disorders of the oesophagus. Novel pharmacological approaches to treat oesophageal motor disorders are also discussed. The anatomy of the oesophagus is unique; it is made up of skeletal muscle in the upper one third, a mixture of skeletal and smooth muscle in the middle one third, and smooth muscle only in the distal one third in humans. The upper oesophageal sphincter is composed of all skeletal muscle and the lower oesophageal sphincter of all smooth muscle. The muscularis propria of the oesophagus, similar to the rest of the gastrointestinal tract, is made of two distinct muscle layers that are arranged in a circular …