The Esophagus is a part of the digestive tract formed by a muscular tube of about 30 centimeters, which connects the pharynx with the stomach . It extends from the sixth or seventh cervical vertebra to the eleventh thoracic vertebra. Food passes through it from the pharynx to the stomach. The main function of the organ is to transfer or swallow the ingested food to the stomach. The word esophagus is derived from the Latin oesophagus and this in turn, from the Greek word oisophagos literally “enter for food.”
Summary
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- 1 Anatomy of the esophagus
- 1 Morphology
- 2 Mucous layer
- 3 Submucosa layer
- 4 Own muscular layer
- 5 Adventitious Cloak
- 6 Topography of the esophagus
- 7 Sphincters of the esophagus
- 7.1 The upper esophageal sphincter
- 7.2 The lower esophageal sphincter
- 8 Innervation
- 9 Vascularization
- 2 Esophageal functions
- 1 Physiology of the esophagus
- 2 Mechanisms of swallowing
- 3 Esophageal diseases
- 1 Esophageal reflux
- 2 Mallory-Weiss syndrome
- 3 Barrett’s esophagus
- 4 Esophageal atresia
- 5 Esophageal Cancer
- 4 Embryogenesis of the esophagus
- 5 References
- 6 Sources
Esophagus anatomy
The esophagus is a mucosa-lined muscle duct that connects the pharynx to the stomach. It is found in the paravertebral region, and is originally located behind the laryngeal cartilages, following the inferior border of the inferior constrictor muscle of the pharynx at the height of the sixth cervical vertebra, from where it extends across the entire thorax to the seventh or eighth thoracic vertebrae, in the cardia, which continues with the stomach . [one]
At birth, the length of the esophagus is 8 to 10 cm, doubles in length at 2 to 3 years of age, and reaches 25 cm at puberty.
Morphology
The wall of the esophagus is made up of four layers, which are: mucosa layer, submucosa layer, muscle layer, and adventitia layer. [2]
Mucous layer
- It is a resistant and mucous layer that contains seromucous glands. This mucosa is continually renewed by the formation of new cells.
It is made up of an epithelium, which is divided, in turn, into several sections:
- Basal area.
- Muscular layer of the mucosa.
- Own lamina or chorion.
Submucosa layer
- It is composed of the cellulose plane, which adheres to the mucous layer. It comprises a significant number of blood vessels, nerve fibers, and mucous tubular glands, especially in its lower third.
Own muscular layer
It is an outer robe made up of two layers. One is the external longitudinal, which is vigorous; another is the circular layer, which is deep and thin. This layer includes three segments: the upper esophageal sphincter (EES), the body of the esophagus (CE), and the lower esophageal sphincter (LES).
Adventitious cloak
- It is made up of connective tissue. It is a thin, fibrous layer that wraps around the esophagus. It contains the nervesand vessels that supply and supply the organ.
All of these layers make up the tubular structure of the esophagus. In addition to this structure, there are two valves in the organ, one at the inlet and one at the outlet, which are the upper esophageal sphincter and the lower esophageal sphincter. [3]
Esophageal topography
From a topographical point of view, four parts can be distinguished: [4]
- An upper or cervical portion, which extends from the cricoid cartilage to a horizontal plane formed by the sternal hairpin,
- A middle or thoracic portion, which from this same plane extends to the diaphragm,
- A diaphragmatic portion, which corresponds to the esophageal ring of the diaphragm,
- A lower or abdominal portion between the diaphragm and the stomach
Esophageal sphincters
The sphincter is a ring muscle that opens and closes the opening of a body cavity to release or retain any substance or secretion.
Anatomically and functionally, the esophagus is divided into the upper esophageal sphincter and the lower esophageal sphincter. [5]
The upper esophageal sphincter
The upper esophageal sphincter separates the pharynx from the esophagus. It is formed by a striated muscle , that is to say, voluntary, which starts swallowing.
It is located in the area where the pharynx and esophagus meet. It is made up of a thick striated muscle band, which means that it is voluntary. There, the lower fibers of the pharynx merge with the higher fibers of the esophagus. It is located at the height of the fifth cervical vertebra. It is also known as a “pharyngoesophageal sphincter.” This segment is ring-shaped and wraps around the esophagus like a clamp. It remains closed and only opens when swallowing starts, that is, when the food bolus is passing. The pressures on this segment cause it to adopt a slit shape. [6]
The lower esophageal sphincter
Separate the esophagus from the stomach. This is claimed not to be an anatomical sphincter, but a physiological one. However, a muscle thickening has been found in this area. [7]
It is not really an anatomical sphincter, but a physiological one, since there is no sphincter structure, but it does have high pressure when measured at rest. Its normally high tone decreases, in response to various stimuli such as the arrival of the primary peristaltic wave, distension of the esophagus when it passes the food bolus (secondary peristalsis) and gastric distention. High pressure at rest is maintained by both nerve and muscle contributions, while relaxation occurs in response to neurogenic factors. Its function is exclusively motor propels the food through the thorax in its transit from the mouth to the stomach (it does not perform absorption or digestion functions).
It has an extension of 2 to 4 centimeters and is located in the upper part of the thoracic cavity and in the lower abdomen . When the food bolus reaches the lower esophageal sphincter, aided by gravity , relaxation of this sphincter occurs. This allows food to pass into the stomach. Then the sphincter returns to its normal tone and this prevents gastric reflux. [8]
Innervation
Innervation of the esophagus
The esophageal walls receive both sympathetic and parasympathetic innervation from the myenteric and submucosal plexuses, and are even innervated by somatic motor neurons whose efferent fibers run through the vagus nerves . [9]
Between both layers is a nervous plexus called the Auerbach plexus. [10]
Vascularization
From top to bottom, the esophagus receives blood from the inferior thyroid artery, esophageal branches from the thoracic aorta, and from the left phrenic and left gastric arteries . Venous and lymphatic drainage follows the arteries. [eleven]
The esophagus is irrigated by different arteries depending on the portion that it covers.
- In the neck, it is supplied by the superior esophageal arteries, branches of the inferior thyroid artery that comes from the subclavian.
- In the thorax, through the middle esophageal arteries, through the bronchial and intercostal arteries, which are direct branches of the aorta.
- In the abdomen, through the lower esophageal arteries from the left lower diaphragm and the left gastric artery.
Esophageal functions
The main function of the esophagus is to transfer or swallow the ingested food to the stomach, and its distal end is responsible for preventing, in a retrograde gastroesophageal way, the reflux of those ingested foodstuffs. The primary mechanical force responsible for the movement of food through the esophagus comes from the muscular outer layer.
Esophageal physiology
The esophagus is the initial part of the digestive tract and its function is to transport the food bolus from the pharynx to the stomach , through the chest and prevent backflow. Swallowing is a complex act, in which we can distinguish three phases: [12]
- Voluntary or oral phase
- Pharyngeal phase, involuntary
- Esophageal phase, involuntary.
The three act in coordination in the transport of the food bolus.
Swallowing mechanisms
Swallowing is divided into 3 stages: oral, pharyngeal and esophageal. The oral phase is voluntary. Once the food is in the pharynx , the swallowing process is no longer voluntary and becomes reflex with a neurological control center located in the brain stem. The process begins with the abrupt elevation of the base of the tongue , which pushes the food bolus towards the posterior pharynx , simultaneously producing a forward and upward movement of the larynx that occludes the glottis through the epiglottis, while the nasopharynx is closed by the uvula and the soft palate.
The upper esophageal sphincter relaxes and the constrictor muscles of the pharynx cooperate in propelling the esophageal body of the ingested bolus where primary muscle peristaltic waves drag it into the gastric cavity. Occasionally, contractions occur that are not accompanied by an oropharyngeal phase called secondary waves whose main job is to empty the esophagus of retained food. Non-peristaltic, simultaneous, small-amplitude contractions, which can appear spontaneously, are called tertiary waves.
Esophageal diseases
Esophageal reflux
Esophageal reflux
Esophageal reflux, the term gastroesophageal reflux is a disease that involves the return of the contents of the stomach to the esophagus, and the discomfort and injuries that accompany this abnormal step. It is the transit of content from the stomach to the esophagus and can irritate the esophagus, causing heartburn and other symptoms, bothersome, that deteriorate the quality of life of patients, or complications. [13]
Mallory-Weiss syndrome
They are lacerations to the mucous membrane of the esophagus, usually caused by making prolonged, strong efforts to vomit or cough. It may appear with some frequency at the junction point between the esophagus and stomach and may be accompanied by bleeding.
Tears of the esophagus are associated with alcoholic habits, eating disorders and in some evidences the presence of hiatus hernia is shown as a predisposing condition. They can also be caused by epileptic seizures.
Barrett’s esophagus
It is also called Barrett’s syndrome, which refers to an abnormal change in the cells of the terminal portion of the esophagus.
It is a metaplasia, which can be the result of injuries due to exposure to stomach acid or reflux esophagitis. Which is present in 10% of patients seeking medical attention for gastroesophageal reflux. It is considered a pre-malignant disorder, as it is associated with an increased risk of cancer of the esophagus .
Barrett’s esophagus is caused by gastroesophageal reflux, which allows the contents of the stomach to damage the cells that surround the surface of the lower esophagus. However, not all GER patients develop a Barrett’s esophagus. It was not possible to predict with certainty which of the heartburn patients will have a Barrett’s esophagus.
Esophageal atresia
It is a disorder of the digestive system, in which the esophagus does not develop properly. It constitutes one of the most frequently observed malformative pathologies for surgical treatment in neonatal intensive care units. It is defined as the interruption of the esophageal lumen with or without communication with the airway. Although it is a malformation of the digestive system, it must be included within the congenital malformations that condition the picture of respiratory distress. Because it is an embryopathy, it manifests in a high percentage associated with other malformations such as cardiac, musculoskeletal, anorectal, and genitourinary malformations.
Esophageal atresia is a birth defect, which means it occurs before birth, and there are several types of it. In most cases, the upper part of the esophagus ends and does not connect with its lower part or stomach . The upper end of the lower segment of the esophagus connects to the trachea, a connection called a tracheoesophageal fistula (FTE). Some babies with FTE will also have other problems, such as heart or other digestive tract disorders.
Esophageal cancer
Esophageal cancer
Esophageal cancer is a condition in which cells malignant (cancer) cells form in the tissues of the esophagus.
The wall of the esophagus comprises several layers of tissue, including mucous membrane, muscle, and connective tissue . The cancer esophageal begins inside coating the esophagus and spreads outward to the other layers as it grows.
Esophageal embryogenesis
The formation of the esophagus and trachea comes from a ventral diverticulum of the anterior intestine that will give rise to the trachea in its ventral portion; and in its dorsal portion, to the esophagus. This occurs around four weeks of age of the embryo , where the respiratory diverticulum (pulmonary outline) in the ventral wall of the anterior intestine, gradually separates from the dorsal portion since, in an initial period, the pulmonary outline communicates widely. with the anterior intestine . When it extends in the caudal direction, it is separated by the appearance of two longitudinal ridges, the tracheoesophageal ridges, which when fused later will form the tracheoesophageal septum. [14]
Between the 3rd. and the 6th. week of embryonic life, the anterior intestine of the cardiovascular and respiratory systems is defined . The anterior intestine arises from the endodermal lining of the anterior part of the primitive alimentary canal, which includes not only the esophagus but also the stomach , the portion of the duodenum, anterior to the mouth of the biliopancreatic ducts, the liver and the pancreas .
