As a flexible muscular tube, the esophagus primarily serves to transport food from the pharynx to the stomach and is not itself involved in digestive processes. Heartburn and difficulty swallowing are signs of impairment of the esophagus that require medical evaluation.
What is the esophagus?
The most common complaints associated with the esophagus are heartburn and reflux disease. The esophagus (food pipe) is a stretchable muscular tube that serves as a connecting pathway between the pharynx and stomach primarily to transport food between these two structures. As a result of its elasticity, which allows it to expand to up to 3.5 cm in diameter, the esophagus can adapt to the size of the ingested food to a large extent in terms of shape and expansion. However, this is physiologically impossible at three strictures (cricoid narrowing, aortic narrowing, diaphragmatic narrowing), so that insufficiently chewed food or swallowed foreign bodies can block the esophagus here. In addition, these strictures are of clinical importance because tumors or inflammation manifest mainly at these sections of the esophagus.
Anatomy and structure
In adult humans, the esophagus has a length of 25 to 30 cm with a diameter of about 2 cm and can be divided into three sections. The cervical section joins the larynx (voice box) and extends to the junction with the thoracic cavity. The thoracic section, which runs through the rib cage, is the longest section of the esophagus at about 16 cm and lies initially behind the trachea and later behind the heart. The adjoining esophageal section, about 1 to 4 cm long, passes through the so-called hiatus oesophageus (diaphragmatic opening) into the abdomen (abdominal cavity). The innermost layer of the esophagus consists of mucosa, a thin connective tissue displacement layer, and a muscle layer through which the mucosal surface can be adapted to the food. The middle connective tissue displacement layer contains the glandulae oesophageae (esophageal glands), which form esophageal mucus and ensure the gliding ability of the esophagus. The outermost layer consists of muscle layers that ensure food transport and a connective tissue layer that loosely links the esophagus to adjacent tissue structures.
Functions and Tasks
The main function of the esophagus is to transport ingested food from the pharynx to the stomach, which is centrally controlled by the reflex interaction of the transverse and longitudinal muscles of the middle layer. In addition, the lumen (inner space) of the esophagus is closed at its cranial (belonging to the head) and caudal (lower) ends respectively by so-called esophageal sphincters (sphincter muscles). During the act of swallowing, the cranial sphincter relaxes, allowing food to pass from the pharyngeal space into the esophagus. Via wave-like contractions of the musculature (peristalsis), the food is transported to the lower end. When this peristaltic wave reaches the caudal end, the esophageal sphincter located there reflexively opens and the food can pass into the stomach for digestion. In addition, esophageal sphincter function ensures that aspiration (inhalation of food particles or foreign bodies) does not occur during swallowing and that acidic stomach contents do not flow back into the esophagus and damage the esophageal mucosa. Peristaltic muscle activity also ensures constant self-cleaning of the esophagus. Swallowed saliva additionally serves to neutralize gastric acid in the esophagus.
Diseases
Disorders of the esophagus usually manifest themselves in terms of difficulty swallowing (dysphagia), heartburn, pain behind the sternum (breastbone), and coughing. One of the most common impairments is impaired closure of the lower esophageal sphincter (cardiac insufficiency), which causes acidic and aggressive gastric contents to flow back into the esophagus. This reflux of gastric acid, known as gastroesophageal reflux, causes irritation of the esophageal mucosa, which, if left untreated, can lead to inflammation or reflux esophagitis later in life.In addition, mechanical disorders of the esophagus may be present, which may be related to mucosal outpouchings (esophageal diverticula), acquired dilatation of the esophageal hiatus (hiatal or sliding hernia), or displacement of the esophagus by membranes or narrowing due to scarring or foreign bodies. Restrictions in the mobility of the esophagus are subsumed under the term motility disorders. These include achalasia, in which the lower esophageal sphincter fails to relax; idiopathic diffuse esophageal spasm, which is associated with contractions in the middle and lower segments that restrict peristalsis; and hypercontractile esophagus (also known as nutcracker esophagus), which is characterized by seizure-like long or extremely strong contractions in the distal segment. In a weakened immune system, bacterial, viral and mycotic infections or noxae (including drugs, radiation) can also cause inflammation of the esophagus (esophagitis). Rare carcinomas (esophageal carcinoma or esophageal cancer) manifest predominantly at the three physiologic strictures and rapidly infiltrate and metastasize the surrounding connective tissue of the esophagus.
Typical and common diseases
- Esophagitis
- Esophageal stenosis
- Esophageal diverticulum (esophageal diverticulum)
- Reflux disease
- Diffuse esophageal spasm