This is the portion of the alimentary canal that reaches the stomach from the pharynx . By means of this organ of a muscle-mucous nature, the food bolus passes – that is, the food chewed by the teeth and partially digested by the enzymes of the saliva – which comes from the mouth and is directed to the stomach. The passage of the bolus is facilitated by the contraction of the muscular component present in the esophageal wall.
From a structural point of view, it presents (starting from the outermost layer to the innermost one):
- an external tunic of a connective nature ;
- a muscular tunic made up of striated bundles for the upper two thirds and smooth for the lower one;
- a submucosal layer that contains mucous glands; a mucous tunic ;
- a tunic characterized by papillae that insinuate themselves into the epithelium;
- a layer of multilayered epithelial tissue .
What is the esophagus?
With a diameter of 2.5 cm. approximately, the esophagus is about 25 centimeters long as a whole : it starts from the neck – at the height of the sixth cervical vertebra – to reach, through the thorax, the abdomen up to the height of the eleventh thoracic vertebra, where the its lower end.
Given its length, it is possible to distinguish a cervical portion (about 4-5 cm long, between the sixth cervical vertebra and the second thoracic vertebra), a thoracic portion (about 15 cm long, which is in contact first with the dorsal wall of the trachea, therefore with the bronchus and with the left cardiac atrium), a diaphragmatic portion (approximately 1-2 cm long) and an abdominal portion (which measures approximately 3 cm and which is between the opening esophageal diaphragm and its outlet in the stomach).
It is then characterized by four narrowings which, starting from the top, are distinguished in: cricoid, aortic, bronchial and diaphragmatic narrowing . The beginning of the esophagus corresponds to the cricoid narrowing (the narrowing takes its name from the cricoid cartilage, which is located in contact with the first ring of the trachea, in the shape of a ring); the aortic and bronchial narrowings correspond to the relationship of the esophagus with the arch of the aorta and with the left bronchus; the diaphragmatic constriction , finally, is at the height of the orifice esophageal aperture.
Between one narrowing and another, it tends to dilate slightly forming three spindle-shaped formations called – from top to bottom – cricoaortic spindle, bronchodiaphragmatic spindle and precardial funnel.
Being a rather long organ, it occurs in relation to numerous structures within the human organism. Its cervical part is partly connected to the trachea by means of connective bundles and via the tracheoesophageal muscle , and partly covered by the left lobe of the thyroid . The thoracic part can be divided into two sections : one above and one below the crossing of the esophagus with the left bronchus. A muscle formation similar to the tracheoesophageal muscle joins the left bronchus with the esophagus at the point where the two ducts cross each other: it is the broncoesophageal muscle . Therethe diaphragmatic part of the esophagus corresponds to the section of this portion of the digestive tract which insinuates itself into the esophageal opening of the diaphragm. The abdominal part of the esophagus is in relationship with the liver (anteriorly) and with the abdominal aorta (posteriorly).
The esophagus can be home to many diseases . The most common is gastroesophageal reflux , caused by an insufficiency of the lower sphincter (cardias) which allows the acidic contents of the stomach to rise in the stomach, causing the characteristic burning.
What is the esophagus for?
Its main function is to allow the food bolus to pass from the mouth to the stomach . When the bolus is swallowed it reaches the bottom of the throat, from which it passes into the esophagus through the mouth of the esophagus (a sphincter that opens appropriately and represents the beginning of the esophagus). The bolus then continues on its way to the stomach via the esophagus ; its passage in the stomach depends on the opening of the lower sphincter (cardias) , which connects the esophagus with the stomach and represents its final portion.