The 7 parts of the intestine: characteristics and functions

The digestive system comprises a set of organs in charge of the process of digestion, or what is the same, the transformation of food by hydrolysis into molecules small enough to pass through the membrane cellular plasma. Thanks to the digestive tract, exogenous nutrients reach the cells, which use them for respiration and many other metabolic processes.

The digestive system comprises several functions, among which are the following: transporting the food throughout the body, acid secretion, nutrient absorption and waste excretion are not metabolizable. 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 automatically think of the stomach, the place where the bolus is mixed with many of the digestive juices. Beyond this very interesting structure, another equally essential section is usually more covered: the intestine.

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

• Related article: "Psychology of feeding: definition and applications"

What are the most important parts of the intestine?

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

Adding up all the parts that compose it, the intestine covers up to 7.5 meters in length. This data has a great biological and evolutionary meaning, since the more total tissue surface area, the more nutrients and water absorption can be carried out until the inevitable excretion of food. In addition, to further increase the absorption surface, the intestinal mucosa has small projections, called intestinal villi.

Before continuing, it is necessary to clarify that the intestine is divided into 2 parts: the small and the large. We explore their particularities separately because, despite being part of the same general structure, they fulfill different functions and have a different anatomy. Go for it.

Small intestine

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

Its most important function is the absorption of nutrientsHence, it has specialized structures and further increases 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-shaped 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.

The small intestine daily absorbs hundreds of grams of carbohydrates, about 50-100 grams of amino acids (essential for the formation of proteins) and up to 7 liters of water. Once its general physiology and functionality have been explored, 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 reaches the duodenum already partially degraded thanks to stomach acids, but here an essential substance 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 characteristics of emulsion of fats, proteins, cholesterol and water (the latter corresponds to 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 the substances of the alimentary chyme, which has already been attacked by the 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 done on a small piece of tissue.

3. Ileum

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

The ileum fulfills 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.

• You may be interested in: "Digestive system: anatomy, parts and functioning"

Large intestine

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

Unlike the small intestine, the bolus (at this point known as chyle) is no longer processed here. The large intestine is limited to absorbing minerals, water and vitamins. Next, we will comment on its parts.

1. Duct of the blind

It is the "bag" that forms the first part of the large intestine, connecting the small intestine with the colon.. The function of the cecum is very curious, since it contains symbiotic bacteria capable of degrading substances that cannot be assimilated by humans, such as cellulose. These compounds of plant origin can account for up to 10% of the daily caloric intake.

2. Colon

It is the longest part of the large intestine, measuring 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, giving rise to 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 performance of the intestinal flora, which gives the stool its unpleasant organoleptic characteristics.

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

3. Right

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, that is, the feces proper.

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

4. Year

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

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

Resume

As you can see, 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 breakdown of substances, the intestine is intended to absorb the maximum amount of water, nutrients and usable products before excretion takes place properly bliss.

If we want you to keep a central idea of ​​this space, this is the following: the intestine (especially in its thin portion) has multiple structures cellular and tissue unique in 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. Picked up on January 3 in https://seom.org/info-sobre-el-cancer/colon-recto? start = 2
• Colon, NIH. Picked up on January 3 in https://www.cancer.gov/espanol/publicaciones/diccionario/def/colon
• Duodenum, medlineplus.gov. Picked up on January 3 in https://medlineplus.gov/spanish/ency/article/002347.htm
• Gut, NIH. Picked up on January 3 in https://www.cancer.gov/espanol/publicaciones/diccionario/def/intestino
• Small intestine, NIH. Picked up on January 3 in https://www.cancer.gov/espanol/publicaciones/diccionario/def/intestino-delgado
• Large intestine, NIH. Picked up on January 3 in https://www.cancer.gov/espanol/publicaciones/diccionario/def/intestino-grueso