Human esophagus diagram
- Gross Anatomy
- Layers of the Esophageal Wall
- Mucosa
- Submucosa
- Muscularis Propria
- Adventitia
- Vasculature
- Innervation
- Lymph Drainage
Gross Anatomy
The esophagus, a muscular tube, lies posterior to the trachea and extends from the hypopharynx to the stomach. It is approximately 25 cm in length and descends through the posterior mediastinum in a nearly vertical direction. The esophagus has three natural divisions: cervical, thoracic, and abdominal. The cervical segment, about 5 cm long, starts at the inferior border of the cricoid cartilage and ends at the thoracic inlet. The thoracic segment is the longest, at about 15 cm in length, and extends from the thoracic inlet to the esophageal hiatus of the diaphragm. The abdominal segment is about 5 cm long and begins at the esophageal hiatus and ends at the gastroesophageal junction or cardia. The esophagus is supplied by the inferior thyroid, left gastric, and bronchial arteries, and it drains into the azygos, hemiazygos, and left gastric veins.
Layers of the Esophageal Wall
The esophageal wall is composed of several layers, each with its own unique structure and function. From the lumen outwards, these layers are the mucosa, submucosa, muscularis propria, and adventitia. The mucosa is the innermost layer and is lined by stratified squamous epithelium. The submucosa is a layer of connective tissue that contains blood vessels, lymphatic vessels, and nerves. The muscularis propria is a layer of muscle that is responsible for the peristaltic contractions that move food down the esophagus. The adventitia is the outermost layer and is a layer of connective tissue that anchors the esophagus to surrounding structures.
Mucosa
The mucosa is the innermost layer of the esophagus and is responsible for protecting the underlying tissues from the acidic contents of the stomach. It is lined with stratified squamous epithelium, which is a type of epithelial tissue that is composed of multiple layers of cells. The mucosa also contains numerous mucus-secreting glands, which help to lubricate the esophagus and protect it from irritation.
Submucosa
The submucosa is the middle layer of the esophageal wall and lies between the mucosa and muscularis propria. It consists of loose connective tissue containing blood vessels, lymphatic vessels, and nerves. The submucosa also contains the esophageal glands, which secrete mucus to lubricate the esophageal lumen. The submucosa allows for the movement of the mucosa during esophageal peristalsis and provides a degree of flexibility to the esophageal wall.
Muscularis Propria
The muscularis propria is the muscular layer of the esophageal wall. It is composed of two layers of smooth muscle fibers, an outer longitudinal layer and an inner circular layer. The longitudinal layer contracts to shorten the esophagus, while the circular layer contracts to narrow the lumen. The muscularis propria is responsible for the peristaltic contractions that propel food down the esophagus towards the stomach.
Adventitia
The adventitia is the outermost layer of the esophagus. It is composed of loose connective tissue and contains blood vessels, nerves, and lymphatic vessels. The adventitia provides structural support for the esophagus and helps to protect it from external damage. It also contains the esophageal plexus, a network of nerves that innervates the esophagus.
Vasculature
The vascular supply to the esophagus is complex, originating from multiple arterial sources and draining into a network of venous plexuses. The arteries supplying the cervical esophagus include the inferior thyroid artery, the ascending pharyngeal artery, and the vertebral artery. The thoracic esophagus is supplied by the aorta, the left gastric artery, and the esophageal branches of the intercostal arteries. The venous drainage of the esophagus follows a similar pattern, with the cervical esophagus draining into the inferior thyroid vein and the thoracic esophagus draining into the azygos vein and the hemiazygos vein.
Innervation
The human esophagus is innervated by both the parasympathetic and sympathetic divisions of the autonomic nervous system. The parasympathetic innervation originates from the vagus nerve, which sends branches to the esophageal wall. These branches contain postganglionic cholinergic neurons that innervate the esophageal smooth muscle, glands, and blood vessels. The sympathetic innervation originates from the thoracic splanchnic nerves, which arise from the thoracic spinal cord. These nerves send branches to the esophageal wall that contain postganglionic adrenergic neurons that innervate the esophageal smooth muscle and blood vessels.
Lymph Drainage
The lymphatic drainage of the esophagus is divided into three regions: cervical, thoracic, and abdominal. The cervical region is drained by the deep cervical lymph nodes, which are located along the internal jugular vein. The thoracic region is drained by the paratracheal, tracheobronchial, and esophageal lymph nodes. The abdominal region is drained by the gastric and celiac lymph nodes.