Gastrointestinal physiology in the mouth and esophagus

2021-06-13 10:59 PM

Chewing is the mechanical action of the mouth that crushes food and mixes it with saliva

Gastrointestinal physiology in the mouth and esophagus

The mouth and oesophagus are the first two segments of the digestive tract, which have the following digestive functions:

Receiving food and crushing it into small pieces.

Bring food from the mouth down to the end of the oesophagus just above the cardia of the stomach.

Breakdown of cooked starch.

The mechanical action of the mouth and oesophagus


Chewing is the mechanical action of the mouth that crushes food and mixes it with saliva. Chewing is a semi-automatic movement, sometimes it is done automatically and sometimes it is done actively.

Automatic chewing:

When eating normally, it is an unconditioned reflex caused by food stimulation to the oral mucosa.

Active chewing:

When encountering hard foods that are difficult to chew or in eating and communicating.


Swallowing is a coordinated mechanical action between the mouth and the oesophagus that pushes food from the mouth to the end of the oesophagus, just above the centre of the stomach.

Swallowing is done in 2 stages:

First stage:

As a semi-automatic movement, performed as follows:

Mouth closed.

The raised tongue presses against the roof of the mouth, pushing food into the throat.

Stage two:

When food enters the pharynx, swallowing moves into the second stage and from here swallowing is an unconditioned reflex called the gut reflex.

The gut reflex is a special reflex of the gastrointestinal tract, which is expressed as follows:

When food is stimulated into a certain segment of the digestive tract, that segment and the upper segment will contract while the lower segment expands. Thus, the gut reflex has the effect of pushing food forward.

Due to the intestinal reflex, when food falls into the pharynx, the pharynx will contract, the anterior pharynx (oropharynx) and the upper pharynx (nasopharynx) also contract, the epiglottis covers the larynx, while the first part of the oesophagus dilates. , as a result, food is pushed from the pharynx into the first part of the oesophagus. Here, the food again stimulates the gut reflex and continues to be pushed down. So, wherever the food goes, the gut reflex appears there to push the food down gradually down the end of the oesophagus.

Saliva secretion

Saliva is the digestive juice of the mouth originating from 3 pairs of large salivary glands: parotid, submandibular, and sublingual and from a number of other small glands such as cheeks, tongue...

Saliva is a mixed secretion of the upper glands. Quantity is about 0.8 - 1 liter/24h.

The composition and effects of saliva

Saliva is a liquid, viscous, foamy, pH near neutral (about 6.5), consisting of the following main components:

Salivary Amylase (ptyalin) :

Is an enzyme that digests glucide, works in a neutral environment and has the effect of breaking down ripe starches into the double sugar maltose.


Has the effect of making food pieces stick together, smooth and easy to swallow, and at the same time protects the oral mucosa against harmful agents in food.


There are many types of Na+, K+, Ca2+, Cl-, HCO3-... In which, only Cl- has digestive effects through the mechanism of increasing salivary amylase activity.

Some special ingredients:

Saliva also has white blood cells and antibodies, so it has an anti-infective effect.

ABO blood group antigen is also secreted in saliva, so we can determine blood group based on saliva.

Some viruses that cause diseases such as mumps, AIDS... are also found in the saliva of patients with these diseases.

Mechanism of saliva secretion

Saliva is secreted by the parasympathetic nervous system.

Normally saliva is also excreted in small amounts, except during sleep.

During meals, salivary secretion is enhanced because the parasympathetic cord is stimulated by two types of reflexes:

Unconditioned reflex:

Caused by food irritation to the oral mucosa. In addition to food, a few other factors can also stimulate the oral mucosa, causing unconditioned reflex secretion of saliva, for example, increased salivation in people with stomatitis, in teething children...

In addition, stimulating some other places such as the intestines, uterus... also increases saliva secretion according to unconditioned reflexes, for example, increased salivation in pregnant women, in people infected with worms...

Conditioned reflexes:

Caused by food-related factors:


Taste and appearance of food.

The noises, words, thoughts associated with eating and drinking...

In children, up to 3 - 4 months of age, the new salivary glands develop completely, by 4 - 5 months, children's saliva often secretes a lot due to the stimulation of the tooth germ, called physiological salivation.

Absorption in the mouth

The mouth does not absorb food but can absorb some drugs such as:


Nifedipine ...

These medications can be taken under the tongue to relieve angina or lower blood pressure.

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Gastrointestinal physiology