Some parts of our body, we take for granted will always work. The oesophagus or gullet is one of those organs. The oesophagus or esophagus, as it can be known, is a 25cm long tube that works to transport food from the mouth to the stomach. The organ originates at the inferior border of the cricoid cartilage, at the level of about C6 and ends at the cardiac orifice of the stomach. It is positioned superiorly and descends into the superior mediastinum of the thorax, between the trachea and the vertebrae before entering the abdomen through the oesophageal hiatus, an opening in the diaphragm.
The structure of the oesophagus is similar to that of other organs in the alimentary tract. The outer layer of connective tissue or adventitia covers a muscle layer which includes external longitudinal muscle and inner circular muscle. The muscle progressively moves from voluntary striated muscle, to voluntary striated and smooth muscle to smooth muscle only. The muscle surrounds submucosa and mucosa. Peristalsis, a muscle contraction that moves in a rhythm, moves the food through the oesophagus. Pathologies can include these muscle layers hardening, which can cause difficulty in swallowing through a loss of muscle contractions.
Ensuring that the oesophagus keeps air out and allows gastric contents through, are two sphincters, known as the upper and lower sphincters. Sometimes they can malfunction and allow gastric contents through, which could cause heartburn. The upper sphincter is placed between the pharynx and oesophagus. It is constricted to prevent air getting into the oesophagus and produced by the cricopharynxgeus muscle. The lower oesophageal sphincter can be found in the lower half of the tube, from the gastro-oesophageal junction. Occasionally, the lower sphincter can be too firm and allow too little food through. As the oesophagus moves from upper to lower, the mucosa change from oesophageal to gastric. The sphincter is functional but involuntary, formed by the angle of the oesophagus entering the stomach, the compression of the intra-abdominal walls, the aid of the mucosa folds and the right crus of the diaphragm, a tendon that is tethered for muscular contraction. During peristalsis, the sphincter allows food in the stomach by relaxing, but when at rest, it is closed to help prevent the reflux of gastric contents acid into the tube. There are four places in the oesophagus where food or foreign objects could lodge. These are the arch of the aorta, the cricoid cartilage, the left main stem of the bronchus and the diaphragmatic hiatus.
The blood supply to the oesophagus can be categorised as to where they receive their supply: either from the thorax or the abdomen. The thorax is supplied from branches of the thoracic aorta and the inferior thyroid artery whereas veins include branches of the azygous veins and the inferior thyroid vein. The abdominal part of the oesophagus receives blood supply from the left gastric artery (of the coeliac trunk) and left inferior phrenic artery. The veins could run through one of two ways: to the portal circulation through the left gastric vein or to the systemic circulation through the azygous vein. This connects both the portal and systemic venous systems, known as the porto-systemic anastomosis. The nerve supply includes the oesophageal plexus which combines the parasympathetic vagal trunks and cervical and thoracic sympathetic trunks.