A Simple Guide to Digestion of Food in the Mouth and Gullet

Teeth are classified as incisors, canines, premolars and molars.

Incisors are primarily used for biting pieces from foods such as raw carrots or apples and peeled but uncut bananas while molars are used primarily for grinding foods after they are already in bite size pieces inside the mouth.

Human teeth play an important part in eating.

They prepare food for swallowing and digestion.

They break down food into smaller pieces with each tooth type doing an individual task.

Canine teeth tear food and premolars mash and grind it, and molars handle most of the overall chewing.

The tongue pushes food into the right position and saliva starts to break it down and moistens it to facilitate swallowing.

What happen when a person grows old and have no teeth or if the teeth are decayed and hurt a lot?

A Person cannot chew properly if he or she does not have teeth or have teeth that are painful which make food particles more difficult to swallow and digest.

The mouth also is also very important in the digestive system but it does much more than get digestion started.

The tongue allows us to taste

The lips that line the outside of the mouth both help hold food in while we chew.

The hardest substances in the body the teeth are also necessary for chewing (or mastication) the process by which we tear, cut, and grind food in preparation for swallowing.

Chewing allows enzymes and lubricants released in the mouth to further digest food.

Saliva is a watery substance secreted daily (0.75-1.5liters) located in the mouths of humans and secreted by the salivary glands.

Human saliva is 99.5% water while the other 0.5% consists of electrolytes, mucus, glycoproteins, enzymes and antibacterial compounds such as secretory IgA and lysozyme.

The enzymes found in saliva are essential in beginning the process of digestion of dietary starches and fats.

These enzymes also play a role in breaking down food particles entrapped within dental crevices, protecting teeth from bacterial decay.

Furthermore saliva serves a lubricating function, wetting food and permitting the initiation of swallowing, and protecting the mucosal surfaces of the oral cavity from desiccation.

The digestive functions of saliva include moistening food and helping to create a food bolus.

This lubricating function of saliva allows the food bolus to be passed easily from the mouth into the esophagus.

Saliva contains the enzyme amylase, also called ptyalin, which is capable of breaking down starch into simpler sugars that can be later absorbed or further broken down in the small intestine.

Salivary glands also secrete salivary lipase (a more potent form of lipase) to begin fat digestion.

Salivary lipase plays a large role in fat digestion in newborn infants as their pancreatic lipase still needs some time to develop.

It also has a protective function, helping to prevent bacterial build-up on the teeth and washing away stuck food particles.

The production of saliva is stimulated both by the sympathetic nervous system and the parasympathetic.

The saliva stimulated by sympathetic nerves is thicker while saliva stimulated by the parasympathetic nerves is more watery.

Sympathetic stimulation of saliva is to facilitate respiration whereas parasympathetic stimulation is to facilitate digestion.

TABLE OF CONTENT

Chapter 1 Why Teeth are So Important

Chapter 2 Saliva

Chapter 3 Oral Phase

Chapter 4 Pharyngeal Phase

Chapter 5 Esophageal Phase

Chapter 6 Digestion in the Mouth

Chapter 7 Swallowing