The oesophagus is a hollow organ that extends from the hypopharynx at the level of the cervical vertebral C6 to the stomach. It descends downward on the body midline into the superior mediastinum of the thorax, positioned between the trachea and the vertebral bodies of T1 and T4. It passes through an opening on the right crus of the diaphragm called the oesophageal hiatus at T10, as it descends from the thoracic to the abdominal cavity, where it joins to the stomach. There are two oesophageal sphincters present in the oesophagus, known as the upper and the lower oesophageal sphincters, which prevent the entry of air and reflux of gastric content, respectively.
- The upper Oesophageal Sphincter is located at the junction between the pharynx and the oesophagus. It normally constricts to prevent the entrance of air into the oesophagus. It is a striated muscle and produced by the cricopharyngeus muscle.
- The lower Oesophageal Sphincter is located at the junction between the stomach and the oesophagus called the gastro-oesophageal junction statute to the left of the T11 vertebra. The lower sphincter does not have any specific sphincteric muscles. It is classified as a physiological sphincter and is identified by the change from oesophageal to the gastric mucosa. The sphincter functions by four main factors:
- The oesophagus enters the stomach at an acute angle.
- The walls of the intra-abdominal section of the oesophagus are compressed when there is a positive intra-abdominal compression due to respiratory phrases.
- There are prominent mucosal folds at the gastro-oesophageal junction, which aid in obstructing the lumen.
- The right crus of the diaphragm has a clamping effect.
During eating or oesophageal peristalsis, there is rhythmical, wave-like contractions and relaxation of the muscles of these sphincters to allow food to enter the stomach. In resting, so when not eating, this sphincters function is to prevent the reflux of acidic gastric contents into the oesophagus.
The inner wall of the oesophagus is lined with a mucosa membrane. Beneath the mucosa membrane lies, the submucosa and beneath the submucosa is the muscularis propria. Instead of a serious membrane on the outside of the oesophagus, there is an adventitia of fibrous connective tissue.