Esophagus

The esophagus (Latin: oesophagus) is a fibromuscular tube-shaped and elongated digestive system's and gastrointestinal tract's organ connecting the pharynx with the stomach. The esophagus provides the food and liquid transport by peristaltic muscle contractions to lower gastrointestinal tract parts.

 

Esopahgus anatomy

The esophagus is approximately 25 centimeters long and 2 centimeters wide. It starts at the inferior edge of cricoid cartilage at the sixth cervical vertebra (C6) level. It goes in the neck region and thoracic and abdominal cavities. The pharynx most distal part, known as the laryngopharynx, is above the esophagus, and the esophagus is its continuation.

From the thoracic cavity to the abdominal cavity, it gets through the diaphragm. In the thoracic cavity, the esophagus locates in the superior and posterior mediastinum. The esophagus ends at the eleventh thoracic vertebra level (T11) and passes into the stomach through the cardiac orifice of the stomach.

 

Esophagus parts

The esophagus has three anatomical parts: cervical, thoracic and abdominal.

 

Cervical part

The cervical part extends from the esophageal opening at the cricoid cartilage's inferior border to the thoracic inlet, also known as the superior thoracic aperture at the first thoracic vertebra level (T1). Anterior to it is the jugular incisure of the sternum. This part is around 5 centimeters long.

 

Anatomical relations

The esophagus cervical part is a continuation of the hypopharynx. It goes behind the trachea and connects with it through the loose connective and muscular tissue. Posterior locate the sixth to seventh cervical (C6 - C7) and first thoracic vertebra (T1) bodies connected to the esophagus with the prevertebral fascia and muscles.

At the sixth cervical vertebra level, the thoracic duct lies on the left side. Close to the thoracic part anterolateral goes the carotid sheath and thyroid gland's lobes. Inferior thyroid artery and recurrent laryngeal nerves also are next to the cervical portion.

 

Thoracic part

The thoracic part goes from the thoracic inlet and sternal notch to the esophageal hiatus located in the diaphragm. The thoracic portion goes from the first to the tenth thoracic vertebra (T1 - T10), and it situates in the superior and posterior mediastinum. This part contains curves and anatomical and physiological constrictions.

The upper thoracic part locates in the thoracic cavity's superior mediastinum. It lies between the vertebral column and trachea. The lower thoracic part goes in the posterior mediastinum. The total length of this part is around 17 - 19 centimeters.

 

Anatomical relations
  • Anterior to thoracic part locate trachea, left main bronchus, aortic arch, right pulmonary artery, esophageal plexus, pericardium, anterior vagus nerve, and left atrium. Part goes behind the aortic arch at the fourth thoracic (T4) to the fifth thoracic (T5) intervertebral disc level.
  • Posterior to thoracic part locate the thoracic vertebra bodies and thoracic duct, azygos and hemiazygos veins, posterior intercostal arteries, posterior vagal nerve, mediastinal pleura, descending aorta. At the eighth to ninth thoracic vertebrae level (T8 - T9) esophagus crosses the aorta.
  • On the left side, locate the left subclavian artery, left vagus nerve, thoracic duct, aortic arch, left inferior laryngeal nerve, and descending aorta.
  • On the right side, locate the mediastinal pleura, azygos vein, right vagus nerve, right main bronchus.

 

Abdominal part

The abdominal part extends from the esophageal hiatus to the stomach's cardiac orifice at the eleventh thoracic vertebra level (T11). Anterior is the seventh rib's cartilage and the end of the sternum. It is the shortest part - 1 to 3 centimeters long.

The esophagus goes through the diaphragm by esophageal hiatus made by diaphragm's right crus muscular fibers at the tenth thoracic vertebra (T10) level. It reaches the cardiac orifice at the eleventh thoracic vertebra (T11) level. The abdominal part covers the peritoneum.

 

Anatomical relations

The esophagus has an attachment to the diaphragm by phrenicoesophageal ligament made up of pleura, subpleural fascia, transverse fascia of abdomen and peritoneum, and phrenicoesophageal fascia.

  • Anterior to the abdominal part locate the liver, left vagus nerve, esophageal plexus, and posterior surface of the heart.
  • Posterior finds the eleventh thoracic vertebra body, right vagus nerve, both crus of the diaphragm, left inferior phrenic artery, and aorta.
  • On the right side locates the liver, but on the left - stomach fundus.

 

Curves

The esophagus has two slight curves in the coronal plane, and it slightly deviates from the midline. It deviates to the left side in the neck part. But in the middle behind the left bronchus - to the right side from the midline. At the end of the thoracic portion, the esophagus deviates again to the left side. Curves form the appearance of the reversed letter "S."

 

Narrowings

The esophagus has four anatomical narrowings:

  • Pharyngoesophageal constriction at the esophageal opening level located at the sixth cervical vertebra level (C6); approximately 1.5 centimeters wide; corresponds to the upper esophageal sphincter's location;
  • Aortic constriction is located in the point where the esophagus crosses the aortic arch; it is at the fourth thoracic vertebra level (T4); it is 1,5 - 1,6 centimeters wide;
  • Bronchial constriction happens at the point where the esophagus crosses the left main bronchus at the fifth thoracic vertebra level (T5);
  • Diaphragmatic or phrenic constriction is at the tenth thoracic vertebra level (T10), where the esophagus goes through the diaphragm.

Esophagus also can have physiological narrowings. The first is below the bronchial constriction, and it happens when atrial dilatation is present. The second narrowing is at the point where the esophagus crosses the aorta at the eighth and ninth thoracic vertebrae level (T8 - T9), and it happens in case of atherosclerosis. The esophagus has one more constriction at the level of the sternum's superior border.

 

Sphincters

The esophagus has two sphincters located in its superior and inferior parts, preventing the stomach acid's backflow in the esophagus and air passage to the stomach when the digestion is not present. Sphincters are known as the upper and lower.

 

The upper sphincter

The upper sphincter makes the striated skeletal muscles, and it is the anatomical sphincter. It locates between the pharynx and esophagus. The junction is called the pharyngoesophageal junction. The fibers from the cricopharyngeus muscle make it with help from the inferior pharyngeal constrictor muscle fibers. It prevents air from the airways going further into the digestive system's parts by staying in a constricted position.

 

The lower sphincter

The lower sphincter is more physiological. It makes the longitudinal and circular smooth muscle cells, the right crura of diaphragmatic muscle, and the fibers from the phrenoesophageal ligament. It locates between the stomach and esophagus left to the midline at the eleventh thoracic vertebra level (T11).

The junction place is called the gastroesophageal junction. In the place where the sphincter locates, the gastric mucosa changes the oesophageal mucosa. Several anatomical features help the lower sphincter. The esophagus has an acute angle where it meets the stomach. The mucosa contains prominent folds at the junction, which helps to constrict the esophagus. When positive intrabdominal pressure is present, the walls of the esophagus are in a compressed condition.

 

Esophagus histology

The wall of the esophagus is composed of four layers:

  • Mucosa
  • Submucosa
  • Muscular layer or muscular propria
  • Adventitia or serous layer

 

Mucosa

Mucosa covers non-keratinized stratified squamous epithelium. In the stomach's cardia part, the mentioned mucosa change into the simple columnar epithelium. The place is known as the Z line - the squamocolumnar junction, and it has an irregular zigzag shape. Mucosa contains lamina propria and lamina muscularis mucosa. Mucosa contains individual lymphatic aggregates.

 

Submucosa

The submucosa contains mucus-producing esophageal glands, which lubricate it and facilitates the ingestion of food bolus. The oesophageal glands are acinotubular mucous glands. In the region close to the pharynx, the glands are simple in form. Still, the abdominal esophagus' glands closely resemble the stomach's cardiac glands and are called esophageal cardiac glands. Esophageal glands can contain endocrine cells.

Submucosa also contains many blood and lymph vessels, nerve plexuses, and dense irregular connective tissue, including a relatively massive amount of elastic and collagen fibers. Submucosa's nerve plexuses are also known as the Meissner's plexus.

The mucous membrane and submucosa contain many muscle fibers allowing the esophageal folds to smoothen when swallowing bolus. Mucosa and submucosa make in the longitudinal direction going seven to ten plicas. It is the reason why the esophagus in the cross-section looks star-shaped.

 

Muscular layer

The muscular part is very thick and has two layers. The outer or external is longitudinal, and the inner is circular. The thickest part of the layer is around the entrance to the stomach. Between the muscle cells is a significant amount of elastic fibers helping to move the hard and rough food particles through the esophagus. In the muscular part, striated skeletal muscles change the smooth muscles.

The upper one-third contains only striated skeletal muscles, the middle one-third has striated skeletal and smooth muscles, but the lower one-third contains just the smooth muscle fibers.Nerve cells are between the outer longitudinal and inner circular muscle fibers. They form the muscular layer's nerve plexus, also called the Auerbach's plexus.

 

Adventitia/serosa

The adventitia layer forms fibrous tissues covering the cervical and thoracic parts. The abdominal parts cover the peritoneum or serosa instead of the adventitia.

 

Esopahgus functions

The esophagus's primary function is to transport the partially digested food from the pharynx to the stomach.

  • Esophageal glands produce mucus, lubricating the bolus and helping in its transportation.
  • Esophagus transport the food by rhythmic wave-like muscle contractions and motion of circular muscular tissue called peristalsis. Contractions go downwards from the superior to inferior esophagus parts. These muscular contractions move the bolus further. Contractions of smooth muscles happen above the bolus, while below is the relaxed part, and that's how the bolus moves. Peristalsis divides into primary and secondary contractions. Secondary peristalsis clears any remained food particles.
  • The esophagus not only moves the food further inside the body. It helps to move it outside of it in case of vomiting in various diseases, issues (hyperemesis gravidarum or the morning sickness in pregnancy), or stimulation of gag reflex, so it also has a protective role.

 

Neurovascular supply of esophagus

Arterial blood supply

All esophagus parts with the arterial blood supply provide esophageal branches from various arteries. Esophageal branches from the inferior thyroid artery (from the thyrocervical trunk) provide the cervical part's arterial blood supply.

The thoracic part is perfused by the bronchial arteries and esophageal branches from the thoracic aorta. The abdominal part gets arterial blood supply from the left gastric artery - a celiac trunk branch. Left inferior phrenic artery from abdominal aorta also perfuses abdominal portion.

 

Venous drainage

The cervical part is drained by the inferior thyroid veins carrying blood next to brachiocephalic veins and next to the superior vena cava. The thoracic part is drained by the esophageal plexus to oesophageal veins and hemiazygos vein next to azygos vein system carrying blood to superior vena cava. Also, the inferior thyroid, intercostal and bronchial veins help to drain the middle part of the esophagus. The abdominal part is drained by the left gastric vein to the portal vein's system. It also drains via the azygous vein.

 

Lymphatic drainage

Lymphatic drainage for the esophagus provides various lymph node groups. The superior one-third drains into deep cervical lymph nodes, the middle one-third to superior and posterior mediastinal nodes, but the lower third drains to celiac and left gastric lymph nodes.

 

Innervation

The esophagus is supplied by the autonomic nervous system's fibers primarily via the sympathetic trunk (sympathetic fibers) and vagus nerve (CN X) (parasympathetic fibers). Sympathetic fibers from spinal nerve T1 to T10 segments participate in esophagus innervation via the sympathetic trunk. Parasympathetic neurons innervate the striated muscles and the upper esophageal sphincter via the vagus nerve (CN X) from the nucleus ambiguous.

The visceral motor neurons from the dorsal motor nucleus act through connection with the esophageal myenteric nervous system and innervate the smooth muscles and the lower esophageal sphincter. The parasympathetic fibers stimulate glandular secretion of the mucosal glands of the esophagus and initiate muscular contractions. The sympathetic and parasympathetic nervous systems regulate the glandular secretion of these glands.

The parasympathetic nerve supply comes from the vagus nerve's dorsal nucleus (CN X) via the recurrent laryngeal nerve's esophageal branches. The sympathetic nerve supply comes from the cervical and thoracic parts of the sympathetic trunk.

The upper one-third's mucosa, glands, and striated skeletal muscles innervate esophageal branches from the recurrent laryngeal nerve, vagus nerve (CN X) branch. The sympathetic trunk cervical part's fibers provide sympathetic innervation.

The thoracic part's mucosa, glands, and striated skeletal muscles innervate esophageal branches from the esophageal plexus (vagus nerve (CN X)). Sympathetic trunk fibers provide sympathetic innervation. The abdominal part innervates esophageal branches from the esophageal nervous plexus and superior gastric plexus from the vagus nerve (CN X).

 

Barett's esophagus

Barett's esophagus characterizes by changes in the cells lining the gastroesophageal junction point caused by acid reflux. Cells can change their type, size, or shape as well. They can start abnormal growth. The mucosa thickens and remains red when exposed to acid. Typically esophageal mucosa has light pink color or pinkish-white color. Barett's esophagus's most common cause is gastroesophageal reflux disease.

 

Gastroesophageal reflux

Gastroesophageal reflux disease (GERD) or acid reflux in which stomach acid regularly or periodically flows back in the esophagus because of the weak lower esophageal sphincter. Acid reflux presents with heartburn and chest pain, regurgitation, chronic cough, nausea, laryngitis.

 

Symptoms

Barett's esophagus can present without any symptoms. Barett's esophagus symptoms include a burning sensation at the lower part of the esophagus and regurgitation, chest pain can be present, and it can be difficult to swallow the food. Usually, the symptoms are related to the same symptoms as acid reflux disease, as it is the leading risk factor causing the condition.

 

Risk factors

The most common risk factors are:

  • GERD
  • Positive family history
  • Increased age (individuals after 50 usually develop the condition)
  • Male gender
  • Smoking
  • Alcohol consumption
  • Obesity (abdominal obesity)

 

Monitoring the condition

Barett's esophagus increases the risk of cancer development. Healthcare professionals suggest doing the endoscopic check-ups one year after the diagnosis, and if there are no changes, repeated endoscopy once every three years.

 

Esophagus cancer

Esophageal cancer is one of the most common cancers in the World, with high death rates affecting any part of the esophagus. The most common risk factors are:

  • Positive family history
  • Increased age (people after 55 years are more likely to develop cancer)
  • Male gender
  • Smoking
  • Alcohol consumption
  • Obesity
  • Presence of GERD
  • Barett's esophagus
  • Poor and unhealthy nutrition
  • A diet with a lack of vegetables and fruits and a high amount of meat
  • Hot liquid consumption
  • Radiation treatment for upper abdomen and chest
  • Injury to the esophagus
  • Achalasia
  • Human papillomavirus infection
  • Other cancer type presence or history (throat, mouth, lung)

 

Cancer types

The most common esophageal cancer type is squamous cell carcinoma, followed by adenocarcinoma. Squamous cell carcinoma most often affects the upper and middle parts, but adenocarcinoma - the lower regions.

 

Symptoms

Esophageal cancer, usually in the first stages, does not have any symptoms. Still, it can present with burning sensation and chest pain, pressure feeling, and weight loss. It can be challenging to swallow, chronic coughing and hoarseness, tiredness, vomiting can be present. Esophageal bleeding can be present, resulting in a black or dark stool.

 

Prevention

Prevention includes:

  • Quitting smoking
  • Reducing the amount of alcohol consumption
  • A healthy diet with vegetables and fruits
  • Losing weight
  • Managing the GERDS
  • Monitoring the Barett's esophagus