The large intestine is the last stage of the” journey ” of food in the body. There is its final processing, digestion and preparation for excretion from the body. We often underestimate the role of the large intestine, as it performs many important functions that are not related to digestion. Let’s find out how this organ works, its functions, and what the billions of microorganisms that live in our intestines are for.
Structure of the large intestine
The large intestine got its name because of the greater wall thickness and the size of the lumen compared to the small intestine. Its average length is 1.5 meters. The large intestine consists of three sections:
- Cecum with the Appendix
- The colon (ascending, transverse colon, descending and sigmoid)
- Rectum (supra-ampullary, ampoule, and anal canal)
Between the small intestine and the initial part of the large intestine, there is a valve that opens in one direction (from the small intestine to the large intestine).
The lining of the large intestine:
The mucous membrane protects the intestinal wall from the harmful effects of digestive enzymes and dangerous substances that may be in the feces. The cells of the colon mucosa produce mucus and enzymes necessary for the digestion of food residues.
The mucous membrane has the form of crypts or reservoirs. They are needed for the accumulation of fecal masses until they are removed outside. In these reservoirs, water and nutrients are absorbed, after which the feces become more dense and ready to leave the body.
The submucosal base contains single lymphatic follicles and immune cells.
The muscle shell consists of two layers. The circular layer ensures the promotion of fecal masses to the rectum. The longitudinal layer, or longitudinal bands, is much shorter than the length of the colon. They provide folding of the intestine, which is literally assembled by longitudinal tapes. This is how bloating of the intestine (gaustra) is formed.
The serous membrane consists of a thin, smooth tissue that reduces friction between the colon, peritoneum, and internal organs.
Functions of the large intestine
The large intestine can be compared to a thrifty housewife who selects the remnants of useful and necessary food in the gruel, which she got from a more picky and wasteful neighbor-the small intestine.
But the completion of digestion and excretion of feces is not the only function of the large intestine. Thanks to the billions of beneficial microorganisms that live there, our immune system is formed and maintained, heat and energy are formed, vitamins and other useful substances are produced, and toxins are neutralized.
Digestion in the large intestine
Liquid food gruel gets from the small intestine to the thick intestine, where it is further broken down. The digestive juice of the colon consists of water, mucus, salts, and enzymes-lipase, nuclease, peptidase, alkaline phosphatase, and others. It is worth noting that the activity of these enzymes is 25 times lower than the activity of small intestine enzymes. This is because most of the nutrients are processed and absorbed in the small intestine, and high enzyme activity is not needed for the final breakdown. In addition, an important role in this process is played by the intestinal flora, which we will talk about a little later.
In the large intestine, water, salts, amino acids, fatty acids, glycerin, and monosaccharides are absorbed. These processes take some time. Therefore, undigested food residues accumulate in the crypts of the intestine, where they lose water and substances necessary for the body, are processed by bacteria and soaked in mucus. Thus, fecal masses are formed, which, with the help of contractions (peristalsis) of the muscle layer, move to the rectum and are stored in its ampoule. When it is filled, the receptors on the mucous membrane are irritated and give a signal to the brain about the need to remove feces from the body.
The last stage of food digestion is associated with the formation of a certain amount of harmful substances or xenobiotics. These are mainly products of the breakdown of amino acids-phenols, indole, skatol and hydrogen sulfide, which give the excrement a characteristic smell and are essentially poisons for the body.
Interestingly, skatol, which is the most “odorous” component of excrement, is part of perfume flower compositions, essential oils, and even used in the food industry for flavoring cheese, ice cream and sweets. Unexpected, isn’t it? It’s hard to believe, but skatol and indole in small amounts have a delicate floral aroma, and in slightly more concentrated ones – creamy-milky. So the well-known smell is just a highly concentrated floral fragrance.
Fortunately, the body has a whole mechanism for inactivating xenobiotics. Some of them are excreted from the body in an unchanged form or are processed by intestinal microorganisms. The other part passes through the portal vein into the liver, where they are decontaminated.
Flora of the large intestine and its functions
Speaking about the functions of the large intestine, it is impossible to ignore the microorganisms that populate it. Their number exceeds the number of all cells in our body, and they weigh from 3 to 5 kilograms. Now you can understand why thorough washing of the intestines gives an imaginary effect of weight loss. Maybe some people are confused by the presence of life inside us, but this evolutionarily formed symbiosis is primarily necessary for humans.
Let’s look at the functions of the intestinal flora:
— Digestion. Intestinal microorganisms use special enzymes to break down the remains of proteins, fats and carbohydrates and promote the absorption of water, trace elements and other necessary substances.
— Vitamin production-synthesis of B, D, PP, K, E, biotin and folic acid.
— Participation in the processes of fermentation and putrefaction. In fact, the composition of our flora and the processes that prevail in the intestine depend on our diet. Rotting does not cause us very good associations, however, it is quite a natural process of breaking down the amino acids of the protein. When rotting, toxic by-products are formed – skatol, indole, and others. With small amounts of them, the body is able to cope, but if there are a lot of poisons, they literally poison the body. Therefore, too much protein in the diet or a violation of their digestion in the small intestine can have undesirable consequences.
Fermentation processes occur when carbohydrates are consumed. A side effect of fermentation is the formation of gases. The processes of rotting and fermentation are completely normal and are inherent in absolutely all people, both meat lovers and vegetarians.
In our intestines, under the influence of clostridium and some types of lactic acid bacteria, the result of fermentation can be alcohol. Medicine has known cases when people after eating carbohydrates in the literal sense of the word got drunk. This is due to the peculiarities of the intestinal flora.
– Protective function. The natural and evolutionary struggle for the existence of a normal intestinal flora helps a person to get rid of harmful microorganisms.
— Neutralization of toxic substances. Microorganisms perform the function of a sorbent-they capture and remove harmful substances.
— The release of heat and energy as a result of fermentation. Thanks to the intestinal flora, a person receives up to 10% of the heat that is generated in the body.
— The formation of the immune system and its modulation. The intestine contains up to 70 % of the lymphocytes of the entire body, its mucous membrane is literally saturated with immune cells. Under the influence of intestinal microorganisms, antibodies are synthesized and antigens are recognized. The bacteria produce signaling substances that help the immune cells to migrate to the site of intruders and recognize them.
The intestinal flora affects the immune system and thus can help reduce the symptoms of allergies. Therefore, many doctors recommend allergy sufferers to put in order the digestive system, in particular the intestines.
The microflora of the large intestine is bacteria, fungi and protozoa. They enter the human body with the first meals, multiply and remain there forever. It is worth noting that each person has their own, individual set of microorganisms, which includes about 500 of their species and depends on many factors – the type of nutrition after birth (natural or artificial), lifestyle and habitual diet, the presence of diseases and bad habits, etc.
Our flora is so sensitive to food that if you followed a vegetable diet, and then switched to meat, then quite quickly the microorganisms that process vegetables will replace the” lovers ” of meat. There are studies that confirm that the species composition of the flora under certain conditions can change within a few hours. You now understand why the analysis of feces for flora is completely uninformative. In order to evaluate the analysis, you need to know the norm. And it is individual for each person, and even changes depending on the circumstances.
The intestine, without exaggeration, can be called the most popular organ that everyone tries to clean. Competition with it, can make, perhaps, only the liver and kidneys. We are frightened by kilograms of toxins and slags that prevent us from living normally. At the same time, these stereotypes are so strong that even completely healthy people, under the influence of advertising pressure, begin to feel an urgent need to clean something.
It is a big mistake to compare the intestines with a water pipe, which can be washed with water and various “cleaning products” – apple juice, sorbents, cocktails with vinegar and soda, and laxatives. In fact, it is a complex system, interference in which can lead to a violation of digestion and the immune system.
There is no scientific justification for the fact that toxins, feces and slags accumulate in the intestine during life. Our liver, kidneys and intestines perfectly cope with decontamination and elimination of harmful substances, microorganisms and toxins without outside help.
Intestinal juice contains a lot of mucus, which is sometimes mistakenly considered harmful. But we have already seen that this is not the case. In addition, the temporary accumulation of feces in the reservoirs of the large intestine is also incorrectly explained. These are not slags at all, but the remains of undigested food, from which the body still needs to get water and nutrients. Removing them from the body before the end of the digestive process is contrary to physiology.
Enemas and washings should be carried out strictly for medical reasons – for poisoning and intoxication, when it is urgently necessary to remove harmful substances from the body. Also, cleansing is carried out before surgical operations and examination of the intestine. In all other cases, the purification of the intestine can only do harm.
Keep an eye on the health of the intestine and do not get carried away with its “cleansing”!