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Anatomy of the Throat and Esophagus

  • 0:06 Deglutition
  • 1:16 Divisions of the Pharynx
  • 3:05 Larynx and Epiglottis
  • 5:22 Esophagus and Peristalsis
  • 6:42 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

After food has been partially broken down in the mouth, it moves through the pharynx, or throat, and the esophagus. In this lesson, you will learn how food is swallowed and how it is propelled by peristalsis through the esophagus.

Deglutition

The digestive system allows us to take in food and break it down into basic nutrients that can be absorbed into the blood and used by the body. We previously learned that the mouth breaks food down mechanically with the process of chewing. We also learned that food is broken down chemically in the mouth with the presence of enzymes in the saliva called salivary amylase.

Once a bite of food is mixed with saliva and broken down by the teeth, it has been transformed into a slippery mass that can be easily swallowed. In this lesson, you will learn about the process of swallowing and the structures of the throat and the esophagus.

To help understand this stage of digestion, let's visit with Frank. Frank recently finished a long day at work, and his stomach was growling. So, he stopped by the local hot dog stand for a quick bite to eat.

Frank's teeth and saliva broke down his first bite of hot dog, and the slippery mass is now ready for deglutition. This is the term used to describe the act or process of swallowing. It will help you remember this term if you note that the root of the word comes from the Latin language and means to 'gulp or swallow.'

Divisions of the Pharynx

The three parts of the pharynx
Pharynx Divisions

During deglutition, or swallowing, the partially digested food passes out of the mouth and into the pharynx. The pharynx is what you might commonly refer to as your throat. Anatomically, it is described as the passage that leads from the cavities of the nose and the mouth to the rest of the alimentary canal. So we see that the pharynx is the upper part of the alimentary canal, which we previously learned is the name used to describe the continuous tube that travels through the body and allows for digestion and absorption of nutrients.

An interesting point about the pharynx is that it not only carries the foods and drinks that you consume; it also carries air, which passes through on the way to the lungs. Now, you swallow hundreds of times a day and likely do not give the process much thought. However, there is a well-orchestrated series of events that must happen so that food and drink you swallow doesn't 'go down the wrong tube,' so to speak.

So how does swallowing prevent food and drink from passing into the wrong tube? Well, to explain this, we need to take a closer look at the anatomy of the pharynx. We see that the pharynx has three divisions. The superior division is called the nasopharynx. It's the part of the pharynx that is continuous with the nasal passages and nose. It's easy to remember this division because the word 'naso' means nose. The next division is the oropharynx. It's the part of the pharynx that lies at the back of the mouth. This division is also easy to remember because the word 'oro' means mouth. The lower division of the pharynx is called the laryngopharynx. It is the lower part of the pharynx that leads to the rest of the alimentary canal. You can recall this term by remembering that the word 'laryngo' means larynx. We will describe the larynx shortly.

Larynx and Epiglottis

Location of the larynx
Larynx Diagram

You can see from looking at the different divisions of the pharynx that food must be routed properly to make it down the alimentary canal. For example, if Frank's ability to swallow is compromised, his chewed-up hot dog could go out of his nose. But luckily for Frank, when he swallows, a flap called the soft palate works properly. This is a soft flap of tissue at the roof of the mouth that closes the nasopharynx during swallowing.

When Frank swallows his hot dog, the soft palate rises and directs the food mass down into the oropharynx. The next possible place that the food mass can get off track is if it were to pass into the larynx. The larynx is described as the air passageway to the lungs. Because the larynx contains the vocal cords, many people refer to it as the voice box. When Frank swallows his hot dog, the larynx rises, causing its opening to be covered by the flaplike epiglottis. The epiglottis is a flap of cartilage that guards the larynx during swallowing.

So we see that during the act of swallowing all undesired routes are blocked off. The tongue blocks the mouth, the soft palate closes off the passage to the nose and a flap called the epiglottis flops over the passage to the lungs. This is the well-orchestrated process of swallowing, and like we said earlier, you do this hundreds of times a day.

The process usually runs very smoothly, but you may have noticed that it doesn't always work so well, especially if you try to talk while swallowing. When you do this, it's possible to 'short-circuit' your routing mechanism. Because talking requires the larynx to be open, food can manage to enter the respiratory passage. This triggers a reflexive coughing, which forces air out of the lungs in an attempt to expel the food that went down the wrong tube.

Once Frank's bite of hot dog enters his pharynx, the process of swallowing - and all digestion from this point on - is under reflexive control and no longer under his voluntary control. We previously learned that the parasympathetic nervous system is the division of the nervous system that is under involuntary control, and we see that the parasympathetic nervous system plays an important role in the digestion of food.

Esophageal muscles move in a wavelike pattern to transport food
Esophageal Muscles

Esophagus and Peristalsis

Food is moved through the pharynx and then enters the esophagus. This is the muscular tube that connects the throat to the stomach. Your esophagus is about 10 inches long, and it acts only as a passageway for food and drink. The esophagus passes behind the airway to the lungs and in front of the spinal column. It pierces the diaphragm before reaching the stomach.

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