The 7 parts of the intestine: characteristics and functions.

A summary of the parts of the intestine, described according to their physical characteristics and functions.

The digestive tract comprises a set of organs responsible for the process of digestion, i.e. the transformation of food by hydrolysis into molecules small enough to cross the cell plasma membrane. Thanks to the digestive tract, exogenous nutrients reach the cells, which use them for respiration and many other metabolic processes.

The digestive tract comprises several functions, including the following: transporting food throughout the body, secretion of acids, absorption of nutrients and excretion of non-metabolizable wastes. Without a doubt, understanding human life as it is without this system would be completely impossible.

When we think of the digestive system, we tend to think automatically of the stomach, where the food bolus mixes with many of the digestive juices. Beyond this very interesting structure, another equally essential section is often more obscured: the intestine.

In this article we will see what the parts of the intestine are and how they function in the process of digestion and evacuation.

What are the most important parts of the intestine?

The intestine is the part of the digestive tract that lies between the stomach and the anus. It is a a long, tube-shaped organ (located in the abdomen) in which the digestion process is completed, as most of the food is absorbed here.It is here that most of the nutrients and water that are ingested during the eating process are absorbed.

Adding up all its component parts, the intestine covers up to 7.5 meters in length. This fact makes great biological and evolutionary sense, because the more total surface area of tissue, the more nutrients and water can be absorbed until the inevitable excretion of food. In addition, to further increase the absorption surface, the intestinal mucosa has small projections, called intestinal villi.

Before proceeding further, it is necessary to clarify that the intestine is divided into 2 portions: the small and the large intestine.. We will explore their particularities separately because, although they are part of the same general structure, they have different functions and have a different anatomy. Let's get to it.

The small intestine

The small intestine can be defined as a thin, tube-shaped organ that connects the stomach to the large intestine. It is approximately 6 meters long, which is why it must present several folds and creases to be located in the human abdomen.

Its most important function is the absorption of nutrientsThe most important function is the absorption of nutrients, which is why it has specialized structures to further increase the available surface area without compromising the viability of the organ. Some of them are the following:

• Circular folds: transverse folds about 8 millimeters high and 5 centimeters long that present the mucous membranes of the small intestine. They increase the absorption surface by 3.
• Intestinal villi: finger-like structures that cover the small intestine and give it a velvety appearance.
• Microvilli: extensions of the plasma membrane of enterocytes, cells of the intestinal epithelium. They increase the absorption surface by 20 times.

The small intestine absorbs hundreds of grams of carbohydrates, about 50-100 grams of amino acids (essential for protein formation) and up to 7 liters of water daily. Having explored its general physiology and functionality, we can briefly describe its parts.

1. Duodenum

It is the first part of the small intestine, located between the stomach and the middle section of the small intestine, also known as the jejunum.. Food is already partially degraded in the duodenum by stomach acid, but here a substance essential for the absorption of nutrients is released: bile.

Bile, secreted in the liver and stored in the gallbladder, is released into the duodenum after food intake. It is composed of bile salts with the characteristics of an emulsion of fats, proteins, cholesterol and water (the latter accounting for 97% of the total). Thus, the absorption of vitamins, minerals and other nutrients begins in this portion of the small intestine.

2. Jejunum

This term refers to the part between the duodenum and the ileum.. Its function is the absorption of substances from the food chyme, which has already been attacked by bile salts. The jejunum has a large number of circular folds and intestinal villi, in order to maximize the absorption surface. Thanks to them, a not inconsiderable amount of absorptive work is carried out in a small portion of tissue.

3. Ileum

The jejunum and ileum are somewhat difficult to distinguish with the naked eye, as there is no exact separation between the two. In general, the ileum is "less": 1 centimeter smaller in diameter, less circular folds and villi and thinner walls..

The ileum has absorption, secretion and motility functions, although to a lesser extent than the jejunum. Even so, it is of essential importance: vitamin B12 and most of the bile salts are absorbed here.

Large intestine

The large intestine is defined as a long, tube-shaped organ that connects to the small intestine at one end and to the anus at the other. It is shorter in length than the small intestine, but it is still enormous, considering its location. considering its location: we are talking about approximately 1-1.5 meters.

Unlike the small intestine, the processing of the alimentary bolus (at this point known as the chyle) is no longer carried out here. The large intestine is limited to absorbing minerals, water and vitamins. Here are the parts of the large intestine.

1. Cecum duct

It is the "pouch" that forms the first part of the large intestine, connecting the small intestine to the colon.. The function of the cecum is very curious, as it contains symbiont bacteria capable of degrading substances that are impossible for humans to assimilate, such as cellulose. These compounds of vegetable origin can account for up to 10% of the daily caloric intake.

2. Colon

It is the longest part of the large intestine, with almost 1.5 meters in length and 6.5 centimeters in diameter.. This structure is responsible for extracting water, nutrients and electrolytes from partially digested food, resulting in feces.

When the food mass reaches this point, almost all the nutrients and 90% of the water have already been absorbed. Therefore, its function is the final absorption and action of the intestinal flora, which gives the stool its unpleasant organoleptic characteristics.

Unfortunately, the colon is probably familiar to you for more than just its physiological characteristics. In terms of incidence, colorectal Cancer is the third most common type of neoplasm, just after lung and breast cancer.just after lung and breast cancer. The average age of presentation is 70-71 years, although it can also occur in younger people.

3. Rectum

It is the last section of the digestive tract, located immediately after the sigmoid section of the colon. It has a length of about 15 centimeters, and it is the place of reception of the waste materials that remain after digestion. after digestion, i.e. the stool itself.

This is one of the most important organs for understanding human defecation. The rectal ampulla is a place of reception of feces and, when its walls are distended by the presence of organic matter, the nervous receptors of the vegetative system provoke the evacuation desires with which we are all familiar.

4. Anus

It is an orifice common to many animals through which the excretion of feces into the environment takes place, since the sphincter that regulates the defecation process is located here. The anal canal extends from the rectum to the perianal skin and is lined by mucous membranes. and is lined by a mucosa that covers the internal sphincter.

The internal lining layer of the anus is divided into 3 sections: glandular, transitional and squamous. This structure measures approximately 4 centimeters and is composed of 4 muscle groups involved in defecation.

Summary

As you may have noticed, each part of the intestine has a specific function and plays a fundamental role in the process of digestion.. From the movement of the food bolus to the degradation of substances, the intestine aims to absorb the maximum amount of water, nutrients and usable products before excretion itself takes place.

If we want you to keep a central idea of this space, it is the following: the intestine (especially in its small portion) presents multiple cellular and tissue structures unique to humans, in order to increase the absorption surface as much as possible without compromising the functionality of the organs involved.

Bibliographic references

• Colon cancer, SEOM. Retrieved January 3 at https://seom.org/info-sobre-el-cancer/colon-recto?start=2.
• Colon, NIH. Retrieved January 3 at https://www.cancer.gov/espanol/publicaciones/diccionario/def/colon.
• Duodenum, medlineplus.gov. Retrieved January 3 at https://medlineplus.gov/spanish/ency/article/002347.htm.
• Intestine, NIH. Retrieved Jan. 3 at https://www.cancer.gov/espanol/publicaciones/diccionario/def/intestino.
• Small intestine, NIH. Retrieved Jan. 3 at https://www.cancer.gov/espanol/publicaciones/diccionario/def/intestino-delgado.
• Large Intestine, NIH. Retrieved Jan. 3 from https://www.cancer.gov/espanol/publicaciones/diccionario/def/intestino-grueso.