BOWEL ELIMINATION: TECHNIQUES AND FACTORS THAT AFFECT IT - ANATOMY AND PHYSIOLOGY - 2025

The intestinal elimination is the process by which food waste are eliminated from the body in digestion; It is the last link in the chain of processes carried out by the digestive system. Individuals need to restore or meet minimal energy and metabolic requirements to carry out their physiological processes.

This restoration process is done mainly through diet; that is to say, feeding. The start of feeding is the first stage of the digestion process, in which successive and logical stages are described, such as ingestion, digestion, absorption, assimilation, and egestion.

The importance of knowing the physiology and anatomy inherent to the intestinal elimination process lies in the fact that numerous pathological processes are associated with its modification and, therefore, the diagnosis of clinical entities could be helped or be based on the recognition of their alterations.

Anatomy

The digestive system comprises a series of structures derived from the embryonic endoderm. Each of these has a role in the digestive process and a predominant activity. For example, the small intestine is characterized as an organ whose predominant function is the absorption of various nutrients.

Regarding intestinal elimination, the portion of the digestive system that is closely related to this is the large intestine.

The large intestine, like most of the digestive system, has 4 layers in its constitution, from the inside out, described as mucosa, submucosa, muscular and serous.

The main difference with the small intestine is that the large intestine does not have villi or connivent valves but, on the other hand, it has a large number of Lieberkuhn's glands.

It begins at the ileo-caecal valve and from an intestinal cul-de-sac - also known as the cecum - its approximate length ranges from 1.20 m to 1.60 m.

It is divided into various portions, which are divided as follows: ascending colon, transverse colon, descending colon and sigmoid colon, which ends in the upper portion of the rectum.

Physiology

In short, the digestive process is made up of various stages or phases. The initial stages include the ingestion of plant or animal products, followed by the extraction of the necessary nutrients and substances from these foods.

Later comes the disposal of everything that is not useful or that is capable of generating some damage to the organism; the latter is known as intestinal elimination.

The predominant function of intestinal elimination lies in two well-described physiological processes: intestinal motility, also known as peristalsis; and the absorption, not so much of nutrients, but of water and sodium.

Peristalsis consists of involuntary contraction and relaxation movements of the intestinal walls that promote the movement of the contents of the organ.

The muscular layer of the intestine has longitudinal and circular muscle fibers, which are electrically connected through gap intercellular bridges.

These muscle fibers contract in response to the propagation of slow, almost continuous electrical waves. In turn, these waves are divided into slow and spike.

Slow waves

Slow waves control gastrointestinal motility almost entirely and continuously, but have the particularity that by themselves they do not trigger action potentials, but rather depolarize the membrane at rest.

Spike waves

Spike waves, also known as spike potentials, are true action potentials, which are generated in response to changes in the membrane by altering resting membrane potentials.

For the contraction to take place, depolarization causes an opening of calcium-sodium channels, unlike in other types of nerve fibers where fast sodium channels open.

In the case of the intestine, the calcium-sodium channels have a slow and sustained opening, which explains the long duration of the action potential and the appearance of slow and tonic contractions. This entire motility system is commanded by the autonomic nervous system.

Pathologies

In the context of intestinal elimination there are various pathologies capable of altering the physiological processes inherent to egestion and, therefore, expressing its symptoms in the form of alteration of the frequency, quality, quantity or aggregates of the stools. Among the most prominent pathologies are the following:

Diarrheal syndrome

It is defined according to the World Health Organization (WHO) as an increase in stool frequency at a rate of more than 3 times a day, and a decrease in stool consistency.

It is classified as acute or chronic diarrheal syndrome depending on the length of time, and its etiology ranges from viral infections to more complex conditions such as Crohn's disease.

Constipation

The antithesis of diarrhea includes in its definition a decrease in the frequency of bowel movements. It can also be associated with changes in its consistency.

Its etiology is also multifactorial; in adults the most common cause is functional constipation.

Malabsorption syndrome

It is a syndrome characterized by the difficulty or inability to absorb certain nutrients, which generates a deficit of these in the body.

One of the most frequent causes is celiac disease, to which the presence of fat in the stool or steatorrhea is attributed as one of its symptomatic manifestations.

Bowel elimination techniques

They are all those techniques whose final objective is the promotion of fecal elimination. Some of these include the following:

- The education of individuals regarding foods that may cause delay or slowing down of their intestinal motility. Such is the case with foods rich in pectin, such as bananas.

- Report on foods that can help the formation of the fecal bolus, as is the case of insoluble fibers such as wheat and whole vegetables.

- Use of substances that promote peristalsis, such as laxatives, if necessary.

- Carry out manual or surgical maneuvers if they are useful to remove possible obstructions in the intestine; for example, digital rectal examination in fecaloma or surgery in intestinal obstructions.

References

1. Diarrhea. Recovered from: who.int
2. Procedures related to disposal. Chapter IV. Recovered from: san.gva.es
3. Treaty of medical physiology. 11 Edition. Editorial Elsevier Spain. Physiology of the digestive system.
4. Heuman DM, Mills AS, McGuire HH. (1997) Gastroenterology. Philadelphia, PA: WB Saunders Co
5. Rodrigo, Luis; Garrote, José A.; Vivas, Santiago (September 2008). "Celiac Disease". Med Clin (Barc) (Review) (Barcelona, ​​Spain) 131 (7): 264-70