Anatomy and Physiology of the Mouth

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  • 0:08 Alimentary Canal
  • 1:07 Saliva and Salivary Glands
  • 2:46 Salivary Amylase and…
  • 4:14 Mechanical Digestion
  • 5:24 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy


The digestive system is a long tube that breaks food down both mechanically and chemically. In this lesson, you will learn about the mouth and how it begins the digestive process - with the help of the teeth and the enzyme called salivary amylase.

Alimentary Canal

The digestive system is basically one continuous tube that runs through your body. The purpose of the digestive system is to break down and absorb the nutrients that you eat and drink. These nutrients are then absorbed into your bloodstream and carried to every cell in your body.

This continuous tube of the digestive system through which food passes, and from which wastes are eliminated, is called the alimentary canal. You can recall this term by relating the word 'alimentary' to 'elementary.' Just as elementary school kids get snacks for nourishment, the alimentary canal provides nourishment to your body.

The alimentary canal is sometimes called the gastrointestinal (GI) tract, or simply, the digestive tract. Whichever name you prefer, the starting place is always the same, and that is the mouth. In this lesson you will learn about the anatomy of the mouth and how it gets the digestive process started.

Saliva and Salivary Glands

Salivary glands located below the tongue and jaw
Sub Salivary Glands

To get a clear understanding of the mouth's role in the digestive process, let's follow Frank as he gets off of work. Frank just put in eight long hours at work and is feeling very hungry. He decides to stop at the local hot dog stand for a deluxe hot dog with all the fixins.

As Frank stands in line, he smells the delicious aroma of the piping-hot hot dogs, and his mouth starts to water. Well, it's not exactly correct to say that Frank's mouth produces water. Instead, it's saliva that is produced. Saliva is an enzyme-containing secretion that moistens food and initiates the digestion of starches.

Just like you, Frank has three pairs of glands that secrete saliva into the mouth. These glands are collectively called your salivary glands. These paired glands are found surrounding your mouth. Two of the paired glands are found at the floor of the mouth. They are the submandibular salivary glands and the sublingual salivary glands, as shown here. We see that the prefix 'sub' means 'below.' The word 'mandibular' means 'jaw,' and the word 'lingual' means 'tongue.' So these pairs of salivary glands are named for their locations below the jaw and tongue. The other pair is found with one in each cheek, lying just in front of the ears.

Interestingly, it is these salivary glands located in the cheeks, known as the parotid glands, that become inflamed in the once-common childhood disease called mumps. Because the inflammation causes the cheeks to swell and appear somewhat lumpy, a person with mumps is sometimes said to have 'chipmunk cheeks.'

Location of the parotid glands in the mouth
Parotid Glands

Salivary Amylase and Chemical Digestion

As we have mentioned, there are enzymes found in saliva that break down starches. These enzymes are called salivary amylase. In normal, everyday life we think of starches as foods such as potatoes, bread and pasta. But in a science lab, we think of starches as a type of food made up of many sugars that are linked together.

Salivary amylase starts to break the links that hold these complex sugars together, essentially breaking them into simple sugars. Chemical digestion is the term used to describe the breakdown of food using chemicals such as enzymes. There are numerous enzymes and chemicals that break down food as it passes through the alimentary canal, but in the mouth, chemical digestion occurs due to salivary amylase.

Before we move on, there's another interesting function of this enzyme. Because salivary amylase breaks down complex starches into simple sugars, we notice a slight sweet taste when we eat foods like potatoes, bread and pasta. So you can thank salivary amylase for helping you taste your food.

Saliva is not only involved in digestion. It also plays a protective role, thanks to additional enzymes and antibodies found within the saliva. Because of these substances, we see that saliva inhibits bacterial growth within the mouth and protects against bacterial infections. Therefore, a person that does not produce sufficient amounts of saliva will be at higher risk for bacterial infection.

Mechanical Digestion

Frank is now ready to dig into his hot dog. Without hesitation, he takes his first big bite, and the process of mechanical digestion begins. The mechanical digestion of food is defined as the physical breakdown of food into smaller pieces. Mechanical digestion occurs in different ways throughout the alimentary canal, but in the mouth it is done by the teeth that chew and grind the food particles in a process called mastication. With the help of the tongue, the chewed food is mixed with saliva to moisten and hold the food together making it easier to swallow.

The alimentary canal, or GI tract, is 30 ft in length
Alimentary Canal

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