Esophagus

The esophagus begins at the cricoid cartilage (at vertebral level C6) and runs to the cardiac orifice of the stomach, a distance of approximately 25 cm.

The esophagus enters the thoracic inlet and transverses the posterior mediastinum before passing through the esophageal opening of the diaphragm (at vertebral level T10) to the stomach. It has a skeletal muscles in its upper third, a combination of smooth and skeletal muscles in its middle third and smooth muscles in its lower third region and is lined by non-keratinized stratified squamous epithelium.

The trachea lies anterior to the esophagus in the neck and superior mediastinum. The esophagus is crossed in the thorax in succession by the arch of the aorta, and the left main bronchus. The lower cervical and thoracic vertebrae lie posteriorly for most of its course, but near the diaphragm, the descending aorta comes to lie posteriorly between the esophagus and the vertebrae.

There are five main sites where the esophagus is constricted:

  1. The junction of the pharynx and esophagus (cricoid origin)

  2. At the aortic arch

  3. At the tracheal bifurcation (vertebral level T4) where the left main bronchus crosses the esophagus

  4. At the left atrium

  5. At the esophageal hiatus

The esophageal sphincters:

  1. Upper Esophageal Sphincter (UES)

    • The UES is skeletal muscle that separates the pharynx from the esophagus.

    • The UES is composed of opening muscles (i.e.,thyrohyoid and geniohyoid muscles) and closing muscles (i.e., inferior pharyngeal constrictor and cricopharyngeus).

  2. Lower Esophageal Sphincter (LES)

    • The LES is smooth muscle that separates the esophagus from the stomach.

    • The LES prevents gastroesophgeal reflux.

Blood Supply

  1. The inferior thyroid artery supplies the cervical esophagus.

    Multiple branches from the descending thoracic aorta supply the thoracic esophagus.

  2. The left gastric artery supplies the abdominal esophagus.

Venous Drainage:

  1. The inferior thyroid vein drains the cervical esophagus.

  2. The esophageal venous plexus drains the thoracic esophagus.

  3. The left gastric vein drains the abdominal esophagus.

Innervation:

The upper portion of the esophagus receives somatic nervous system by the enteric nervous system, which consists of the myenteric plexus of Auerbach only. The enteric nervous system is modulated by the parasympathetic and sympathetic nervous systems.

1. Somatic innervation to the esophagus is provided by the hypoglossal nerve to signal the upper esophageal sphincter to open.

2. Parasympathetic innervation is provided by the recurrent laryngeal nerves.

3. Sympathetic innervation to the esophagus is provided by the enteric nervous system.