Topography and parts of the esophagus
Anatomically, the esophagus begins where the pharynx ends. In an adult, this transition is projected at the level of the 6th cervical vertebra. The organ ends at the transition into the stomach, which corresponds to the level of the 11th thoracic vertebra.
Throughout its entire length (which is about 25 cm), the tube is divided into three topographical parts:
- Cervical part (pars cervicalis) — the uppermost section, originating from the 6th cervical vertebra and extending up to the entrance to the thoracic cavity. Its length ranges from 5 to 8 cm.
- Thoracic part (pars thoracica) — the longest segment of the organ, spanning 15 to 18 cm. It passes through the entire thoracic cavity and ends at the esophageal hiatus of the diaphragm.
- Abdominal part (pars abdominalis) — the shortest fragment, only 1–3 cm long. Immediately after passing through the diaphragm, this section flows into the stomach.
Spatial configuration: curves and constrictions
Despite the fact that the esophagus is a tube, its course is not completely straight. The organ is located anterior to the spine and follows some of its curves, as well as adapting to neighboring structures. There are four curves in total:
- two curves are located in the sagittal plane;
- two curves are located in the frontal plane.
Three physiological constrictions located along the course of the organ are of paramount clinical significance. It is in these zones that the lumen of the tube naturally narrows:
- Pharyngeal constriction — located at the very beginning, at the transition site of the pharynx into the esophagus.
- Aortic constriction — formed where the esophagus is crossed by the aortic arch.
- Diaphragmatic constriction — located in the area where the tube passes through the esophageal hiatus of the diaphragm.
Histological structure of the wall
The wall of the organ is ideally adapted for propelling food and consists of three main tunics.
Mucous membrane (tunica mucosa) is lined with stratified squamous epithelium, which protects the tissues from mechanical damage. A characteristic feature of the mucosa is the presence of pronounced longitudinal folds that allow the lumen to stretch during the passage of a large bolus. Proper esophageal glands (glandulae oesophageae) lie in the submucosa, the secretion of which additionally lubricates the walls.
Muscular tunic (tunica muscularis) is responsible for peristalsis. It is formed by two layers: an inner circular and an outer longitudinal layer. The distribution of muscle tissue types along the length of the organ is interesting:
- striated muscle tissue predominates in the upper third;
- it is gradually replaced by smooth muscle in the middle third (mixed section);
- the musculature becomes exclusively smooth in the lower third.
Outer tunic varies depending on the region. The cervical and thoracic parts are covered by connective tissue adventitia (tunica adventitia), which loosely connects the esophagus to surrounding organs. The abdominal part, located in the abdominal cavity, is covered by a serous membrane (tunica serosa).
Blood supply, innervation, and lymphatic drainage
The organ receives its blood supply from multiple sources due to its significant length. Blood supply is provided by branches of the inferior thyroid artery (a. thyroidea inferior), the thoracic aorta (aorta thoracica), and the left gastric artery (a. gastrica sinistra).
Nerve regulation is carried out by the esophageal plexus (plexus oesophageus), which is formed by branches of the vagus nerve (n. vagus) and the sympathetic trunk (truncus sympathicus).
Lymph drainage from various regions is directed to the corresponding regional nodes: cervical, tracheobronchial, mediastinal, and gastric lymph nodes, which ensures reliable immune defense of the organ throughout its entire length.
Briefly: answers to topical questions
What anatomical and physiological constrictions are distinguished in the esophagus?
The esophagus has anatomical and physiological constrictions located at different levels.
Physiological constrictions:
- Pharyngeal — transition of the pharynx into the esophagus.
- Aortic — crossing with the aortic arch.
- Diaphragmatic — esophageal hiatus of the diaphragm.
Anatomical constrictions:
- Cricopharyngeal — at the site of transition of the pharynx into the esophagus (level of the cricoid cartilage, cricopharyngeus muscle — m. cricopharyngeus).
- Aortic — at the site of contact with the aortic arch.
- Bronchial — at the site of contact with the left main bronchus.
- Diaphragmatic — at the site of passage through the esophageal hiatus of the diaphragm.
Which organs are in contact with the thoracic part of the esophagus?
The thoracic part of the esophagus has syntopic relations with the structures of the superior and posterior mediastinum.
Syntopy of the thoracic region:
- Trachea — the esophagus is located posterior to it, projecting from under its left margin.
- Aortic arch (arcus aortae) — at the level of the tracheal bifurcation, the esophagus lies to the left against the posterior-right surface of the aortic arch; the aortic constriction is formed here.
- Initial segments of the left common carotid and left subclavian arteries — the esophagus borders them.
- Thoracic duct — passes between the left common carotid and left subclavian arteries.
- Left recurrent laryngeal nerve (n. laryngeus recurrens sinister) — runs on the left, in the groove between the esophagus and the trachea.
- Vertebral column — the esophagus is located anterior to it; the sagittal curve of the esophagus follows the curve of the spine and is separated from it by prevertebral tissue and fascia.
Which arteries supply blood to the esophagus?
Blood supply to the esophagus is provided by branches of several arteries.
The blood supply involves:
- Inferior thyroid artery (a. thyroidea inferior) — its branches supply the esophagus.
- Thoracic aorta (aorta thoracica) — gives off esophageal branches; the source specifies 3–6 esophageal branches (rr. esophagei) to the esophageal wall.
- Left gastric artery (a. gastrica sinistra) — participates in the blood supply to the lower thoracic and abdominal parts of the esophagus.
Through which veins is venous blood drained from the esophagus?
Venous drainage from the esophagus is carried out via esophageal veins (vv. oesophageales) and associated venous pathways.
Drainage is described along the following pathways:
- Unpaired thyroid plexus (plexus thyroideus impar) — collects blood, including from the esophagus, and drains it into the brachiocephalic veins.
- Azygos vein system (v. azygos) — receives esophageal veins (vv. oesophageales) from the thoracic segment.
- Left gastric vein — indicated for the lower thoracic and abdominal segments of the esophagus.
In the region of the lower third of the esophagus and the cardiac part of the stomach, anastomoses are formed that are clinically significant in portal hypertension.
To easily memorize the three physiological constrictions of the esophagus, you can use the acronym PAD: Pharyngeal, Aortic, Diaphragmatic.
Class and exam questions
At the level of which vertebrae is the esophagus located?
In adults, it begins at the level of the VI cervical vertebra and ends at the transition into the stomach at the level of the XI thoracic vertebra.
How does the type of muscle tissue in the esophageal wall change?
In the upper third of the organ, the muscular coat consists of striated muscle tissue. In the middle third it is mixed, and in the lower third it is represented exclusively by smooth myocytes.
Which coat covers the esophagus externally?
The cervical and thoracic segments are covered by adventitia (tunica adventitia), while the short abdominal segment is covered by a serous coat (tunica serosa).
What else to study on this topic
- Syntopy of the thoracic segment and its relation to the aortic arch
- Histological features of submucosal glands
- Mechanism of formation of the esophageal nerve plexus
- Blood supply characteristics of the abdominal segment
- Lymphatic drainage pathways from the upper and lower thirds of the organ
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