Esophagus (Parts, Curvatures, Constrictions, Layers) - Anatomy

Summary

The video explains the esophagus’s location and subdivisions, its curvatures and constrictions, and the layers that make up its wall.

Location and parts

The esophagus connects the pharynx to the stomach and is about 25 cm long on average. It has three parts:

• Cervical part: Begins at the pharyngeal opening into the esophagus and ends at the superior thoracic aperture.
• Thoracic part: Extends from the superior thoracic aperture to the esophageal hiatus, where the esophagus passes through the diaphragm.
• Abdominal part: Runs from the esophageal hiatus to the cardiac orifice of the stomach.

Curvatures

Although the esophagus descends generally toward the stomach, it does not follow a perfectly straight path. It:

1. Curves slightly to the left near its beginning.
2. Curves to the right in the middle of the thoracic part.
3. Curves back to the left in the lower thoracic region before passing through the diaphragm.

Constrictions

The video distinguishes anatomical constrictions, which are structural, from physiological constrictions, which depend on muscle activity and relax after death.

Anatomical constrictions

• Pharyngoesophageal constriction: At the pharynx–esophagus junction, around C6–C7. It consists of skeletal muscle and closes during breathing.
• Bronchoaortic constriction: Behind the left principal bronchus, around T4.
• Diaphragmatic (phrenic) constriction: At the esophageal hiatus, around T10. “Phrenic” refers to structures associated with the diaphragm.

Physiological constrictions

• A constriction where the esophagus crosses the aorta, around T8–T9.
• The lower esophageal sphincter, where the esophagus enters the stomach, around T11.

The video describes these physiological constrictions as smooth-muscle structures controlled involuntarily by the autonomic nervous system.

Layers of the esophageal wall

From the lumen outward, the wall has these layers:

1. Tunica mucosa

   • Lined by stratified squamous non-keratinized epithelium.
   • Includes mucus glands, blood vessels, nerves, and lymphoid nodules.
   • Supported by the lamina muscularis mucosae.

2. Tela submucosa

   • Loose connective tissue containing esophageal glands that produce lubricating mucin.
   • Also contains esophageal cardiac glands, which produce neutral mucin to help protect the esophagus from acidic gastric contents if reflux occurs.

3. Tunica muscularis

   • Has an inner circular muscle layer and an outer longitudinal muscle layer.
   • The upper third is mainly skeletal muscle; skeletal muscle is gradually replaced by smooth muscle, and the lower third is smooth muscle.

4. Outer covering

   • The cervical and thoracic parts are covered by tunica adventitia, a connective-tissue layer.
   • The abdominal part is covered by tunica serosa, associated with the peritoneum, which provides a smooth surface that allows organs to move with less friction.

Speakers and sources featured

• Narrator: “Meditay,” presenting the anatomy lesson.
• Visual material: Anatomical illustrations and a histology slide are used to explain the esophagus and its wall.