It is important that the esophageal motility occurs in a physiological way.
The possibility of swallowing foods and not suffering from reflux of acidic
material in the throat is the prerogative of a good esophageal peristalsis.
Patients who have the sensation of food stuck in the throat suffer from
alteration of peristalsis; sometimes the sensation of blockage of peristalsis (bolus)
can be caused by severe pathologies such as cancer of the esophagus or less
serious as esophagitis. Never underestimate, therefore, the signs of dysphagia,
that is of bad swallowing.
The transport of the bolus along the esophagus is guaranteed by peristaltic
contractions of the muscles of the wall. The transport speed of the striated
musculature of the upper tract is greater than that of the inferior tract;
overall the bolus takes 20-25 s to reach the entrance of the stomach. Fluids, on
the other hand, pass through the esophagus faster due to gravity; even liquids,
however, generate peristaltic waves; these are very slow and have no effect when
the body is in a vertical position; on the contrary, in lateral decubitus, they
allow the liquids to be transported at a speed equivalent to that of the solid
bolus. Thanks to the effectiveness of the esophageal peristalsis it is possible
to swallow liquids even with the body and the head upside down. The act of
swallowing is reflected and can not be controlled voluntarily. The passage of
the bolus through the pharynx causes coordinated muscular contractions at the
esophageal level. The afferent branch of this reflex arc passes along the
glossa-pharyngeal nerve, while the efferent branch passes through the vagus
nerve. Furthermore, the control of the sequence of muscular stimuli is borne by
the intramural myenteric plexus of the esophagus (Auerbach's plexus).
The mucosa is made up of three layers: covering epithelium (non-keratin layered
flooring type), own tunic and muscularis mucosae.
The outermost layer of the esophageal wall is muscular (muscolaris propriae), and consists of striated (voluntary) muscle fibers in the upper third, smooth (involuntary) muscle fibers in the lower third, while in the middle third the musculature is mixed as both has the transition from one type to another. For the entire length, however, the muscle fibrocellulas are organized in two layers: one with fibers with a circular pattern (more internal) and one with fibers with a longitudinal (more external) pattern; during swallowing these muscles contract, pushing food into the stomach (peristalsis). In the intermediate layer, on the other hand, the esophageal glands (cardial glands) are found, which pour their secretion into the lumen of the esophagus. This secretion allows the esophagus to remain moist. Among the smooth muscle fibrocellulas are nerve fibers belonging to the myenteric plexus of Auerbach which stimulates the esophageal peristalsis. The submucosa presents connective lapse with tubulo-mucous glands of the mucous membranes and nerve fibers of the Meissner plexus that regulate the glandular secretion and the motility of the muscularis mucosae. The lamina propria is richly vascularized and rises in folds.
The outer muscular layer of the esophagus, which has an almost longitudinal
course, results in continuity with the external muscular layer of the stomach.
Also the inner spiral-shaped muscular layer, characterized by fibers with an
almost horizontal course, results in continuity with the stomach wall, even if,
at the level of the cardia, it is divided into a circular middle layer and an
oblique inner layer. At the height of the cardial incision, the muscle fibers of
the inner layer have a spiral-like arrangement. The area between the esophagus
and the stomach is just 2-3 cm below the diaphragmatic hiatus and has the task
of closing the upper portion of the stomach. It is important to close it, to
avoid the reflux of the acidic gastric contents towards the esophagus, with
consequent damage to the esophageal mucosa.
For a long time it was not possible to know the functioning of the
gastro-esophageal sphincter, since histologically in this area the typical
sphincter muscular formation is not found. The sphincter of the lower extremity
of the esophagus is slightly above the point in which leads to the stomach,
above the mucosal limit between the esophagus and the stomach.
The muscle fibers of the esophagus, which follow a course similar to the thread
of a vine, form a sort of "closure". Under physiological conditions, the
esophagus is subjected to a relatively high longitudinal tension, whereby, when
they are drawn, the lumen of the bowel can shrink until it disappears completely.
This mechanism is particularly effective because in the lower portion of the
esophagus the muscle mass increases considerably and because the inclination of
the musk-fibers is greatly reduced, until having an almost horizontal course at
the level of the cardia. Furthermore, the abdominal portion of the stomach is
surrounded by a thick subepithelial venous plexus. The opening of the sphincter
is obtained by reducing the longitudinal tension of the e-sofago; in addition to
peristaltic movements, the lower portion of the esophagus shows upward movement
during swallowing. This prevents the vine-shaped muscle fibers from contracting
forcefully in the longitudinal direction, allowing the lumen of the bowel to
dilate. An inhalation causes a considerable increase in pressure in the
abdominal portion of the esophagus, also called antrum of the heart, which
prevents the passage of the esophageal contents towards the epiphrenic portion.
That is, the bolus remains stationary at that point for the duration of the
inspiration. Therefore, if you inhale deeply while swallowing, you notice an
unpleasant feeling of pressure in the epigastrium.
index of topics of gastroenterology