Digestion in the Mouth

Saturday, January 23, 2021

Digestion begins Here!

The mouth is a very versatile part of the body. It enables you to make inappropriate jokes in class, perform concerts in the shower, kiss your dog on the nose, save someone’s life through mouth-to-mouth resuscitation, and a crowd favorite - eat! Today, we will look at how the various parts of the mouth work in concert to digest the food you eat.  

You walk downstairs and smell freshly baked cookies. Your mouth waters. Or, more accurately, your mouth salivates. When you smell food, the salivary glands release saliva, a fluid made of water mostly, as well as proteins, mucus, minerals, and enzymes. Salivation is the first step in the digestive process. It prepares the mouth to receive and break down food. 


Saliva (a.k.a. spit) serves many important functions, including: the enzyme in it, salivary amylase, breaks down food into a liquid form that is easier for the body to digest. Saliva also serves as an indicator for how well hydrated you are (dry mouth? drink more water!). It also prevents tooth decay by removing bacteria and dead cells from the mouth.  

You have 32 adult teeth that rip and chew your food. There are four types of adult teeth: canines, incisors, premolars, and molars. The canines, or vampire teeth, are the very pointy teeth found on the top and bottom of your mouth. They help tear food apart. The incisors are the front four teeth on the top and bottom of your mouth that hold and cut food. They also sense the texture of your food. The premolars have two cusps and also cut and tear food. They are found right behind your canines and are slightly smaller than molars. The molars are the last kind of adult teeth. They provide broad surfaces on which food is ground into mush.  

You have three types of salivary glands: the parotid gland, the submandibular gland, and the sublingual gland. The parotid glands are the largest of the three types and are found in the cheeks. The submandibular gland is the second largest salivary gland and produces the most saliva (about 65%). It is found on the floor of the mouth. The sublingual glands produce the least amount of saliva (around 5%) and are widely dispersed under the tongue. They are the smallest of the three glands.   

salivary glands

Your tongue is actually a very flexible muscle. The tongue contains nerves, blood vessels, and tiny receptors known as taste buds that are part of what enable you to taste your food. The tongue facilitates movement of food in your mouth, pushing food to your teeth if it needs to be chewed more and down to the throat when you are ready to swallow. 

digestion starts here

Your mouth is responsible for two types of digestion: mechanical and chemical. Mechanical digestion is the process of physically breaking your food down into smaller pieces. Chewing is the first step of mechanical digestion. Chemical digestion is the process of breaking down food molecules through chemical reactions. Like mechanical digestion, chemical digestion begins in the mouth. Saliva’s amylase enzyme helps chemically deconstruct carbohydrates. Stomach acid also plays a role in chemical digestion.  

Though food and air regularly pass through your mouth and down your throat, you rarely choke. This is because there is a leaf-shaped flap of cartilage that acts as a guard to your windpipe. This flap is called the epiglottis. While breathing, the epiglottis remains open, allowing air to pass from your mouth, down the windpipe, to your lungs. When swallowing, however, the epiglottis closes to prevent food from entering your windpipe and choking you. Instead of passing through the windpipe, food travels from your mouth, down the esophagus, to your stomach.    

Four major muscles are responsible for chewing. These four muscles are: the masseter, the temporalis, the medial pterygoid, and the lateral pterygoid. 

The masseter has a rectangular shape, moves your jawbone, and is actually the strongest muscle in the body, capable of exerting up to 200 pounds of pressure. 

The temporalis is a fan-shaped muscle responsible for closing the mouth, moving the jaw side to side while chewing, and grinding food down between the molars. 

You have two medial pterygoid muscles on either side of your jaw that help the jaw move forward, side to side, and down while chewing food. 

The lateral pterygoid functions much like the medial pterygoid, except that it is not responsible for closing the jaw. 

masseter mouth muscles

Once food is a chewed up, round mass, it is called a bolus. Once this bolus has passed through the stomach and undergone more chemical and mechanical processing, it is known as a chyme. 

The roof of your mouth is actually made up of two parts: the hard palate and the soft palate. The hard palate is formed from bones and does not move. The soft palate is made of muscle and is capable of movement. The hard palate accounts for two-thirds of your mouth’s roof and is located in the front of the mouth. The soft palate is located at the back of the mouth, closer to the throat.

anatomy oral cavity

As a recap: salivation occurs when you smell and eat food and is the first step in digestion. Saliva chemically breaks down your food.

You have 32 adult teeth that fall into one of four categories: canines, incisors, premolars, and molars.

You have three types of salivary glands in your mouth: the parotid, submandibular, and sublingual.

Your tongue is a very flexible muscle that pushes food around while eating.

Food undergoes two types of digestion in the mouth: mechanical and chemical. Mechanical digestion physically breaks food into smaller pieces while chemical digestion chemically breaks down food into smaller molecules.

The epiglottis is a flap of cartilage that stands guard over your windpipe and protects you from choking.

The four muscles responsible for chewing are the masseter, the temporalis, the medial pterygoid, and the lateral pterygoid. A round mass of chewed-up food is known as a bolus.

The roof of your mouth has two parts: the hard and soft palate.

Related Links

Digestive System Simple Terms

The path of food through the digestive system

10 Facts about Digestion

Does Eating Turkey Make You Sleepy?


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