The mouth begins the digestion process by breaking down food into a more digestible form. After being ingested through the mouth, food travels down the throat, also called the pharynx. It then passes into the esophagus, then into the stomach. Read on to learn more about the biology of the mouth and its role in digestion. This article also explains the functions of other parts of the digestive system.


The mouth is the starting point of the gastrointestinal (GI) tract. A person’s gastrointestinal tract is made up of hollow organs that connect to each other. The digestive tract is about 8 to 9 meters long and extends from the mouth to the anus. The mouth is made up of several parts that aid in digestion. These parts have different functions.

1. Ingestion

The first stage of digestion is ingestion, during which a person puts food into their mouth with their hands or another utensil.

2. Mechanical digestion

Chewing is the beginning of mechanical digestion. It is the process by which the mouth breaks down large pieces of food into smaller pieces.


The jaws consist of an upper jaw, the maxilla, and a lower jaw, the mandible. When we eat, we separate the jaws to bring food into the mouth.

The lips contain sensory receptors that help assess the texture and temperature of food. The lips and cheeks help hold food in place inside the mouth. The muscles attached to the jaws allow them to move up and down to chew.

The jaws contain teeth that are used to cut, tear, crush and grind food. The first dentition, or milk dentition, includes 20 teeth. An adult dentition has 32 teeth. The cheeks help move food between the teeth for chewing. The tongue is a large muscle that plays various roles in digestion, such as:

sucking food
moving food between teeth
help with swallowing by pushing chewed food to the back of the throat
encouraging the production of saliva, also known as spitting up
absorption of nutrients through its underside.

The tongue also contains many small bumps on its surface, called papillae, which have two different functions.

Mechanical taste buds allow a person to sense the texture and shape of food. Taste buds contain taste buds that allow food to be tasted. Certain flavors encourage the production of saliva and stomach acid, which aids digestion.

3. Chemical Digestion

During chewing, saliva mixes with food and helps soften and break it down. Saliva also lubricates food particles and makes them easier to swallow.
When food and saliva mix, they form a bolus. It is what a person swallows after chewing.


The salivary glands produce saliva, which is made up of the following substances that help in the chemical digestion of food:

lingual amylase and lipase enzymes, which help break down starch and fats

A human has three pairs of large salivary glands in the following places in their mouth:

parotid glands in front and under the ears
submandibular glands under the mandible
sublingual glands under the tongue
The mouth also contains hundreds of smaller salivary glands.

5. Preparation for swallowing

When chewing, the tongue compresses food against the two palates of the mouth. This helps form the food bolus, which can then be swallowed.


The hard palate is the roof of the mouth. The soft palate is located behind, in the throat. It prevents food from entering the nasal cavity.
After the person has finished chewing their food, the tongue pushes the food bolus down the throat. From there it goes down the esophagus to the stomach.

Other parts of the digestive system

Here is the role that other organs play in digestion:

Stomach: Continues the breakdown of food using acids and enzymes.

Pancreas: Produces digestive juices to break down carbohydrates, fats, and proteins that the body secretes into the small intestine.

Liver: Produces bile, a digestive juice that breaks down fats and some vitamins.

Gallbladder: Stores bile and secretes it into the small intestine when needed.

Small intestine: Forms digestive juice which mixes with bile and pancreatic juice to finalize the breakdown of fats, carbohydrates and proteins. It absorbs water and some nutrients.

Large Intestine: Absorbs more water from the gastrointestinal tract into the bloodstream. It breaks down the remaining nutrients to make vitamin K. The remaining waste is turned into stool.

Rectum: Stores stool until the body eliminates it through the anus.

Frequently Asked Questions

Below are answers to the most frequently asked questions about the role of the mouth in digestion.

What are the digestive processes in which the mouth is involved?

The mouth is involved in the following four processes:

mechanical digestion
chemical digestion
nutrient absorption

What are the digestive enzymes present in the mouth?

The mouth contains the enzymes amylase and lingual lipase, which help break down starch and fats.


The mouth is an important part of the digestive process. Digestion begins in the mouth, which breaks food down into smaller particles. Once chewing is complete, food can pass into the esophagus and stomach. The gastrointestinal tract continues to process food before the anus evacuates waste.

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