Published May 21, 2023 by

Digestive System: Definition, Anatomy and Functions


What is the digestive system?

The digestive system is known as the set of organs that are in charge of the digestive process, that is, the transformation of food so that it can be absorbed and used by all the cells of the organism.  In addition to humans, most of the higher animals have a digestive system that performs this function.

During digestion or the digestive process, the different types of nutrients found in the food consumed (carbohydrates, lipids and proteins) are transformed into simpler units, thanks to the different digestive enzymes.  Under these conditions, the most elementary usable parts of the nutrients can be absorbed and then transported through the blood to all the cells of the body, where they are used to obtain energy and carry out all the essential functions for the maintenance and development of life. .

The functional process of the digestive system includes all the events that take place, from the entry of food into the mouth, to the expulsion of feces (indigestible remains) through the anus, passing through the absorption of nutrients through the intestinal walls.  It is a long process, which involves a set of complex mechanisms, in which numerous organs and parts of the body are involved, and which is essential for life, given that human beings (like all animals) are heterotrophs, and therefore Therefore we can only incorporate the organic matter we need through food.

Digestive system anatomy

Food gives the body the energy necessary for life.  The digestive system processes food separating the basic nutrients that can be assimilated by the body. From the mouth, through the stomach and intestines, to the anus, lies the digestive system, which is a long, muscular tube. Food is digested as it passes through the digestive system, which transforms it into elements that can be taken into the circulation. Certain organs (such as the liver, gallbladder, and pancreas) help with digestion.  The parts of the food that cannot be digested are expelled from the body in the form of excrement.

Digestive tube

It extends from the mouth (entrance orifice) to the anus (terminal or exit orifice).  It measures about ten meters in length and is made up of several differentiated portions.


It forms the entrance to the digestive tract.  It is in charge of receiving the food that is ingested and crushing it.  Three main functions are developed: chewing, insalivation and swallowing.


Musculo-membranous cavity that is located at the back of the mouth and communicates at the top with the nasal cavity and middle ear, and at the bottom with the larynx and esophagus.  It has a double function: passage of breathed air and ingested food.


Tube about 25 cm long that connects the pharynx with the stomach. It crosses the diaphragm and is located between the trachea and the spinal column.  Its main function is to carry food to the stomach.


Hollow "J" shaped organ measuring approximately 25 cm in length, situated below the diaphragm.  Two orifices or valves are differentiated: cardia, which communicates with the esophagus, and pylorus, which serves as a limit with the small intestine.  The gastric mucosa that covers it is of special importance to protect it from the acids that are part of the composition of the gastric juice. In the stomach, food is crushed by mechanical agitation and unites with the gastric juice, forming a highly acidic mush called chyme.

Small intestine  

Tubular structure situated below the stomach.  Under normal conditions it can measure between 6 and 7 meters in length and about 3 cm in width.  It occupies most of the abdominal cavity, where it remains rolled up.  Duodenum, jejunum and ileum are three major parts of small intestine.

Large intestine  

It is 1.5 to 2 meters long and extends from the ileocecal valve (which closes the opening of the small intestine) to the anus.  It consists of three segments: blind, colon and rectum, and communicates with the outside through the anus.  Its functions are the absorption of water and minerals and the elimination of waste products through the anal sphincter.

Function of various  parts of digestive system :

The basic function of the digestive system is the transfer of nutrients from the external environment to the internal environment, so that the cells of the organism have molecules that allow their metabolic maintenance and restoration.

The nutrients accessible to the organism can be of very different nature and size.  Those that are small in size can be absorbed without undergoing any change;  while those that have a large size have to go through a fractioning or breaking process that is called digestion.

The digestive system is not an excretory system, since most of the products that come out of it, the feces, correspond to non-absorbed material, bacteria and degraded cells of the digestive system itself.


Chewing triggers the start of the digestive process in the mouth. 

The salivary glands produce saliva, a digestive juice that moistens food for easier transport down the esophagus to the stomach.


The function of the pharynx is therefore to direct air or food to its proper place.  The oropharynx is part of the upper digestive tract, although it also serves as a passage for air in mouth breathing or coughing.  It goes from the pharyngeal entrance to the base of the epiglottis.  When we eat, we introduce food through the oral cavity where we chew it and then push it back with our tongue.  That "back" is the pharynx, a conduit where the already crushed and moist food can continue its process in the body until it reaches the stomach.  The pharynx is where the muscular contractions are carried out that will allow the food to continue its course and reach the esophagus.

The contractions also prevent food from entering the trachea and thus from leaking into the respiratory canal.  The epiglottis is the valve that, with contractions, the pharynx is in charge of closing and preventing us from choking on a piece of food.


The esophagus is the initial part of the digestive tract and its function is to transport the food bolus from the pharynx to the stomach, through the thorax and prevent its reflux.


Functions of stomach includes:

* temporarily store food

* mechanically break food into small particles

* mix the food bolus with the gastric secretion until obtaining a semi-liquid mass called chyme

* chemically digest proteins

* progressive emptying of chyme at a rate compatible with digestion and absorption by the small intestine

* secrete intrinsic factor, which is essential for the absorption of vitamin B12, into the ileum

Small intestine :

Long tube-shaped structure that joins the large intestine to the stomach. Its job is to keep the stomach's digestion going while absorbing nutrients (vitamins, minerals, carbs, lipids, and proteins) and water for the body to use. 

Large intestine

The following activities of the large intestine are all necessary for the body to function properly and include:

* Water absorption and stool formation

* Vitamins, short-chain fatty acids and nutrient recycling

* pH regulation

 *immune function

* function of the appendix