What is digestion? Definition, characteristics and phases

Digestion is a physiological process in which undigested matter is expelled in the form of feces.

In single-celled organisms, such as bacteria, this is essentially the expulsion of unusable material out of the cell. In contrast, in the case of multicellular organisms, such as humans, food goes through a longer process.

Many people confuse excretion with digestion, and although both are related to digestion, they are two different physiological processes.

Human digestion: definition and phases of this physiological process

Before going into more detail with the concept of management, it is necessary to understand how human digestion occurs and the processes that take place in food before it is eliminated as feces..

When we eat, food enters the digestive tract. The main function of this device is to process food to get as many nutrients as possible and to dispose of what is not usable or has been left as waste.

A whole host of organs are involved in the digestion process: mouth, salivary glands, esophagus, stomach, pancreas, liver, gallbladder, small and large intestine, appendix, rectum and anus.

The first place food passes is the mouth. There it is chewed and mixed with saliva, starting digestion and starting its decomposition. In this phase of the digestion of food is called bolus food.

The food bowl goes to the stomach through the esophagus and then reaches the small intestine, where digestion continues. Once the food is digested, the molecules that were present in it can be absorbed more easily.

These nutrients are introduced into the bloodstream, so that they travel to all parts of the body when needed.

Not everything is absorbed in the small intestine. Only the smallest and most soluble substances can be absorbed through the walls of this organ. Those which do not, which are larger and insoluble, in the event that their size has not been reduced by the action of enzymes, cannot be used. This is the pre-digestion phase.

What is digestion?

The part of the food that could not be absorbed in the small intestine passes into the large intestine. There, excess water is absorbed and by the action of bacteria the rest of the food is degraded.

The result is fecal matter, which is mostly water and bacteria, as well as substances that the human body cannot digest, such as cellulose and fiber. In addition to what could not be enjoyed, feces contain substances that could be harmful to the body and must be eliminated.

Bacteria in the digestive system play a very important role for humans, as they digest substances, such as certain types of carbohydrates, and synthesize proteins, such as B and K. They also fight other bacteria that could be harmful. for the body. Human, which cause diseases and digestive problems.

Correctly, the process of digestion occurs when what could not be used by the body is stored in the rectum. This is where, when the signal is given, they are discharged through the anus of waste.

The output of stool is controlled by the anal sphincter, which consists of two parts: the internal sphincter and the external sphincter. If there is debris in the rectum, the anal sphincter stretches and allows stool to come out.

Differences between digestion and excretion

Today, both in general culture and in some textbooks, these two terms are still confused. Although both are two phases present in digestion, they have certain nuances that differentiate them.

Digestion is the removal of things that come with food that cannot be used, such as non-digestible substances and harmful elements. for the human body. This is basically the part of the food that has not been introduced into the bloodstream and that the body has benefited from and that is eliminated as feces.

however, excretion is a process in which what is eliminated are substances that have been used to maintain vital functions. Cells need energy to perform their functions and for this they need nutrients. These nutrients are given in the form of organic molecules, which are crumbled inside the cell and produce energy. The residues of this process leave the cell and are excreted in the urine.

associated problems

Whether due to illness or a poor diet, there may be problems removing feces.

These issues may not be serious and can be resolved over time, however, if they persist you should seek professional help to make sure it is not a more serious issue.

1. Diarrhea

Diarrhea occurs when loose, watery stools are passed because they have been short of passage through the small intestine.

It can be caused by contaminated food and water, viruses, parasites, drug use and abuse, food intolerance and sensitivity, stomach surgeries, upset stomach and colon functioning problems.

2. Fecal incontinence

It is the inability to control when to defecate. This can be the result of loss of control of the sphincters or bowels, so you need to see a professional to help you learn how to control them again.

3. Constipation

Feces are difficult to remove, and they can be dry and very hard. Although being forced may not be able to do a tummy tuck every day, it is considered constipation to do it less than 3 times a week.

4. Encopresi

Encopresis is the involuntary removal of feces in inappropriate places and times. This elimination disorder typically occurs in children as young as 4 years old and can have multiple causes. It usually occurs when excretions retained in the rectum and colon build up, causing bloating in the abdomen, loss of bowel control, and even loss of appetite.

The child cannot control the outflow of feces, which can be both liquid and solid, or be large enough to block the toilet.

In the event that the child has not previously learned to control the sphincters, it is called primary encopresis. On the other hand, if he came to control them before suffering from encopresis, we speak of secondary encopresis. There may be emotional factors behind the child’s encopresis, such as poor family dynamics.

Bibliographical references:

  • Keeton, W. and Harvey, D. (2016). Human digestive system. British Encyclopedia.
  • Pocock, Gillian, (2006). Human physiology (third ed.). Oxford University Press.

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