7 Pharynx and Esophagus

Pharynx

From the mouth the bolus of food enters the pharynx, commonly referred to as the throat, a funnel shaped tube that extends to the esophagus. Swallowed food passes from the oropharynx to the laryngopharynx and into the esophagus. A structure called the epiglottis covers the tracheal opening ensuring food enters the esophagus and not the respiratory system. When food enters the trachea by accident, this often results in a coughing or choking reflex, which can colloquially be referred to as when food “enters the wrong pipe.”

Esophagus

From the pharynx, the esophagus is a long collapsible muscular tube about 25cm long which pierces the diaphragm on the leftward side through the esophageal hiatus. 

The esophagus is lined with smooth muscle which is why swallowing is an involuntary action. These muscles also rhythmically contract in a pattern known as peristalsis. You may have actually been aware of the peristalsis if you have ever swallowed something while sitting upside down. If not, you can try this right now and notice how despite fighting against gravity the liquid will swallow. View peristalsis through the following diagram:

View the esophagus with respect to the pharynx and other structural landmarks:

The esophagus has two key sphincters which look like hatches controlling the entry of food. The upper esophageal sphincter(UES) remains closed until swallowing relaxes the sphincter allowing the transfer of food into the esophagus.  The lower esophageal sphincter(LES) (cardiac sphincter) located about 3cm before the stomach opens to allow food into the stomach.

What Can Go Wrong?

While the esophagus is primarily concerned with propelling food downwards, but it can also elicit vomiting when a gag reflex is initiated.

Heartburn and gastroesophageal reflux disease(GERD) are common issues where the lower esophageal sphincter fails to close following passing of food into the stomach. In these instances acidic stomach acids can reach through the LES and into the esophagus, insinuating a burning sensation around the lower portion of the esophagus which is conveniently located near the heart – hence the name heartburn. If not treated these conditions can worsen to esophageal cancer, ulcers or tears.