Absorption takes place in the large intestine. Absorption of fats in the intestine

During the digestion of food colon plays an insignificant role, since food is almost completely digested and absorbed in the small intestine, with the exception of plant fiber. In the large intestine, chyme is concentrated by absorbing water, forming feces and removing them from the intestines. Absorption of electrolytes, water-soluble vitamins, fatty acids and carbohydrates also occurs here.

During hydrolysis in the large intestine, enzymes that come from the small intestine and enzymes of intestinal bacteria are involved.

The glands of the mucous membrane of the colon secrete a small amount of juice (pH 8.5-9.0), containing mainly mucus and a small amount of enzymes (peptidases, lipase, amylase, phosphatase, nucleases) with significantly less activity than in the small intestine. However, in case of indigestion in the higher parts of the digestive tract, the colon is able to compensate for them by increasing secretory activity.

The regulation of juice production in the colon is provided by local mechanisms. Mechanical irritation of the intestinal mucosa enhances secretion by 8-10 times

. Functions of the large intestine:

AT digestive - in the large intestine, digestion processes are completed under the action of pancreatic, intestinal juices and partial breakdown of dietary fiber and other organic substances by microbial enzymes;

AT suction - absorption of water (1/3), glucose, vitamins, amino acids, salts, partial absorption of food proteins, not digested, and there are no proteins - waste products of microorganisms in a non-hydrolyzed state (absorption is hindered only by the remoteness of protein residues from the intestinal mucosa)

AT regulatory - stimulation immune system(antigenic waste products of microorganisms and undigested proteins) and regulation of the autonomic nervous system;

AT synthetic - biosynthesis of vitamins by the microflora of the large intestine, which are partially used by the body: thiamine (B 1), riboflavin (B 2), pantothenic acid (B 3), folacin (Bc), niacin (PP), biotin (H), pyridoxine (B 6 ), phylloquinone (K) and their absorption;

AT protective - protection of the intestines from pathogenic microorganisms, preventing their vital activity and reproduction through antagonism

In the large intestine, its microflora plays a special physiological role. The microflora is capable of performing three functions: digestive, synthesizing and protective.

It has been proven that the intestinal microflora synthesizes vitamins 1,. IN 2 ,. AT 6 ,. AT 12 ,. RR,. K. It is important that the synthesizing functions are seriously impaired when there is a deficiency in the diet of fiber and organic acids found in vegetables, fruits, as well as when there is an excess diet of refined carbohydrates and billamy. The synthesis of vitamins also decreases with constipation, which contributes to the development of putrefactive microflora.

The protective function of normal microflora is to suppress pathogenic microbes that enter the intestine. For the normal life of microorganisms, a slightly acidic environment and dietary fiber are necessary. The best remedy maintaining the intestinal microflora in an active state are dairy products(act at the expense of lactic acid bacteria), pectins and fiber of fruits, berries, vegetables. Meat promotes the development of putrefactive bacteria. Rotting feces create an alkaline environment and promote the growth of pathogenic microflora.

Escherichia coli synthesize B vitamins. In which, in particular, play the role technical supervision, preventing the endless growth of tissues, supporting the immune system, carrying out anti-cancer protection when protein rots, methane is formed in the large intestine, which destroys B vitamins.

Doctor. Gerzon stated: "Cancer is revenge. Nature for food eaten incorrectly." In his book "Cancer Treatment", he writes that out of 10,000 cases of cancer, 9999 are the result of poisoning with their own feces

Mold, formed during the decay of food, contributes to the development of serious pathology in the body.

Thus, the intestinal microflora:

Forms a normal intestinal mucosa;

Participates in lipid metabolism bile acids;

Regulates water-salt metabolism and gas exchange;

Participates in the creation of general immunity and maintaining it at the proper level;

Synthesizes vitamins. K and groups. B in the large intestine;

Partially breaks down fiber and pectin fibers that were undigested in the small intestine;

Inactivates enzymes:. alkaline phosphatase, trypsin, amylase;

Ferments carbohydrates to acidic products (lactic and acetic acids);

Forms the so-called "secondary flow of nutrients and non-alimentary substances"

. Causes of dysfunction of the large intestine:

Excessive consumption of refined foods (without dietary fiber) and fats, which disrupts the motor and excretory functions and causes intoxication of the body;

o consumption meat products low quality and easily poisoned increases the processes of decay and intoxication of the body;

o consumption of inaccessible or poorly available and at the same time low molecular weight carbohydrates enhances fermentation (noisy) processes and flatulence in the intestines, which increases the risk of intestinal volvulus, hernias and ruptures in the intestines.

Suction is the function of the digestive system, which consists in the absorption of nutrients in the composition of food by the body. The process is provided by active or passive transport of substances through the wall of the organs of the gastrointestinal tract. Absorption occurs over the entire surface of the digestive system, but in some departments it is most active. In particular, the intensity of the process is the highest in and .

The intestine is the main area for nutrient absorption. This function is one of the most important tasks of the body.

Absorption in the small intestine

The small intestine is considered the main compartment for nutrient absorption. In the stomach and duodenum, nutrients are decomposed into their simplest components, which are then absorbed in the small intestine.

Here the following substances are absorbed:

Amino acids. Substances are components of protein molecules.
Carbohydrates. Large molecules of carbohydrates (polysaccharides) that are contained in food are decomposed into the simplest molecules - glucose, fructose and other monosaccharides. They pass through the intestinal wall and enter the bloodstream.
Glycerin and fatty acids. These substances are components of all fats, both animal and vegetable. Their assimilation occurs very quickly, since the components easily pass through the intestinal wall. This is how cholesterol is absorbed.
Water and minerals. The main place of water absorption is the large intestine, however, in the departments small intestine there is an active assimilation of fluid and essential trace elements.

Absorption in the large intestine

The main products for absorption in the large intestine are:

Water. The fluid freely passes through the membranes of the cells that make up the wall of the organ. The process proceeds according to the law of osmosis and depends on the concentration of water in the mucous membrane of the large intestine. Due to the correct distribution of fluid and salts, water actively enters the body and enters the bloodstream.
Minerals. One of the most important functions of the large intestine is the absorption of minerals. These can be salts of potassium, calcium, magnesium, sodium and other vital trace elements. Great importance They also have phosphates - derivatives of phosphorus, from which the main source of energy, ATP, is synthesized in the body.

Malabsorption in the intestine

In some diseases, the absorption of vital components - carbohydrates, amino acids, components of fats, vitamins and trace elements can be impaired. Insufficient intake of these substances in the body triggers a cascade of biological reactions that lead to a deterioration in the patient's condition.

The reasons

All causes of malabsorption can be divided into two main groups:

Acquired disorders. Secondary changes in intestinal absorption are not inherent in the genetic material of the patient. They are provoked by some factor that adversely affects the state of the digestive system and leads to a disruption in the absorption of nutrients.
congenital disorders. Such conditions are characterized by a genetically programmed absence of any enzymes that degrade nutrients. So, with lactose intolerance, a person lacks an enzyme that decomposes this substance, which is why it is not absorbed in the body. Such diseases are called fermentopathies.

Secondary Causes in turn, they are classified into groups depending on what pathologies provoked digestive disorders. It can be not only damage to the gastrointestinal tract, but also pathologies of other organs:

gastrogenic disorders - pathologies of the stomach;
pancreatogenic causes - diseases of the pancreas;
enterogenic causes - intestinal damage;
hepatogenic disorders - causes associated with impaired liver function;
endocrine dysfunctions - changes in work thyroid gland;
iatrogenic factors - disorders that occur against the background of drug therapy some means (NSAIDs, cytostatics, antibiotics), as well as after irradiation.

Symptoms

To general symptoms malabsorption include:

diarrhea, change in the nature of the stool;
heaviness and arising after eating;
increased weakness, fatigue;
pallor;
weight loss.

Depending on what substances are not absorbed by the body, clinical picture diseases can be complemented. So, with a lack of vitamins, visual impairments appear, skin manifestations and other symptoms of beriberi. Fragility of nails and hair, bone pain indicate a lack of calcium. Against the background of insufficient iron intake, the patient develops anemia. Potassium deficiency can adversely affect the functioning of the heart. Vitamin K deficiency can lead to an increased tendency to bleed.

The general range of disorders depends on the severity of malnutrition of the body, the nature causative factor that influenced the development of the disease.

In any case, malabsorption is a serious traumatic factor for the body, adversely affecting its functional activity. Therefore, when this condition is detected, it is urgent to undergo treatment.

Structure

Colon

The large intestine follows the small intestine and has a larger diameter (about 7 cm at the beginning and about 4 cm at the end). The total length of the colon ranges from 1 to 1.5 meters. By appearance the large intestine differs not only in diameter, but also in 1) the presence in it of three external longitudinal muscle strands, or ribbons, which are 1/6 shorter than the intestine itself; 2) characteristic dome-shaped swellings of the wall.

The large intestine is divided into the following sections:

caecum with appendix. The caecum lies below the confluence of the small intestine with the large intestine. The length of the appendix is on average 8 cm; the length of the caecum is about 6 cm and the diameter is 7 - 7.5 cm.
ascending colon
transverse colon
descending colon
sigmoid colon (has S-ob different shape)
rectum ending with a powerful muscular sphincter formed by striated skeletal muscle tissue.

The wall of the large intestine has essentially the same structure as the small intestine. But the colonic mucosa has a smooth surface, no villi. There are no annular folds, but there are small semilunar folds of the mucosa. On the inner surface of the large intestine at the confluence of the small intestine there is damper, consisting of two folds and preventing the return of the food mass into the small intestine. In the mucosa, compared with the small intestine, intestinal glands are not so numerous.

Enzymatic digestion of food due to its own enzymes is practically absent here, because. the intestinal juice of the large intestine contains few enzymes, and the chyme that enters here is poor in undigested nutrients. The large intestine, unlike other parts of the digestive tract, is rich in symbiotic microorganisms, mainly bifidobacteria and lactobacilli. The number of bacteria in the intestine healthy person is about 10 15 . Digestion in the large intestine occurs very intensively under the influence of intestinal microflora. Symbiotic bacteria break down substances that are difficult to digest, such as cellulose, hemicellulose, pectin etc., which are part of the walls of plant cells. The microflora also digests the components of digestive juices. The symbiotic microflora of the large intestine plays an important role in the production of certain amino acids, vitamins (for example, vitamins K and B), in suppressing the growth of foreign, including pathogenic bacteria, in the suppression of putrefactive processes. Thus, the intestinal microflora plays a very important role in maintaining not only the processes of digestion, but also performs other important functions for the human body, including supporting the body's immunity. The caecum is the area where intestinal microorganisms multiply. So, the digestion of food in the large intestine occurs mainly under the influence of natural symbiotic microflora. The intestinal microflora is very sensitive to the action of antibiotics, toxic substances, and stress. The weakening of the microflora leads to a general weakening of the body, a decrease in its protective properties. Simultaneously with taking antibiotics, it is recommended to take multivitamins, preparations of bifido- and lactobacilli. The composition of the intestinal microflora includes putrefactive bacteria, which from the products of protein decay can form toxic substances that enter the bloodstream, but under normal conditions are neutralized by the liver. Therefore, it is necessary to empty the intestines regularly.

The absorption processes continue in the large intestine, but the absorption of water from the food mass occurs especially intensively and in large quantities, so the excrement contains a small amount of it.

With a mixed diet, about 10% of the food taken is not absorbed by the human body. Undigested food debris and dead bacteria, which make up up to 50% of feces, glued together by intestinal juice mucus, are removed through the rectum.

Earlier in our articles it was noted that in the digestion of fats to monoglycerides and free fatty acids, both end products of digestion are first dissolved in the central lipid part of bile micelles. The molecular size of these micelles is only 3-6 nm in diameter; in addition, micelles are strongly charged from the outside, therefore they are soluble in chyme. In this form, monoglycerides and free fatty acids are delivered to the surface of the microvilli of the brush border of the intestinal cell and then penetrate into the recess between the moving, oscillating villi. Here, monoglycerides and fatty acids diffuse from the micelles into the epithelial cells, since fats are soluble in their membrane. As a result, bile micelles remain in the chyme, where they work again and again, helping to absorb more and more portions of monoglycerides and fatty acids.

Therefore, micelles perform the function " crossings”, which is extremely important for the absorption of fats. In fact, with an excess of bile micelles, about 97% of fats are absorbed, and in the absence of bile micelles, only 40-50%.

After entry into epithelial cells fatty acids and monoglycerides are taken up by the smooth endoplasmic reticulum of cells. Here they are mainly used to synthesize new triglycerides, which are later released through the base of the epithelial cells in the form of chylomicrons to pass further through the thoracic lymphatic duct and into the circulating blood.

Direct absorption of fatty acids into the portal circulation. A small amount of short and medium chain fatty acids (which are derived from butterfat) are absorbed directly into the portal circulation. This is faster than conversion to triglycerides and absorption into lymphatic vessels. The reason for the difference between short and long chain fatty acid absorption is that short chain fatty acids are more water soluble and are not normally converted to triglycerides by the endoplasmic reticulum. This allows short chain fatty acids pass by direct diffusion from the intestinal epithelial cells directly into the capillaries of the intestinal villi.

Absorption in the large intestine

Average per day about 1500 ml of chyme passes through the ileocecal valve into the large intestine. Most of the electrolytes and water from the chyme are absorbed in the large intestine, leaving usually less than 100 ml of fluid to be excreted in the faeces. Basically, all ions are also absorbed, only 1-5 meq of sodium and chlorine ions remain for excretion with feces.

Main absorption in the large intestine occurs in the proximal colon, hence the name of the absorptive colon, while the distal colon functions specifically to store faeces until the right time for excretion, hence the name storage colon.

Absorption and secretion of electrolytes and water. The mucosa of the large intestine, like the mucosa of the small intestine, has a greater capacity for active absorption of sodium, and the electrical gradient created by the absorption of sodium ions also ensures the absorption of chlorine. tight contacts between epithelial cells large intestine have a greater density than those in the small intestine. This prevents significant back-diffusion of ions through these junctions, thus allowing the colonic mucosa to absorb sodium ions more completely, despite a higher concentration gradient than would be the case in the small intestine. This is especially true in the presence a large number aldosterone, because it significantly increases the ability to transport sodium.

Like the mucosa of the distal both the small intestine and the colonic mucosa are able to secrete bicarbonate ions in exchange for absorbing an equal amount of chloride ions. Bicarbonates help neutralize the acidic end products of bacterial activity in the colon.
Absorption of sodium and chloride ions creates an osmotic gradient in relation to the colonic mucosa, which, in turn, ensures the absorption of water.

Maximum absorption in the large intestine. The large intestine can absorb no more than 5-8 liters of fluid and electrolytes daily. When the total amount of incoming contents into the large intestine through the ileocecal valve or together with the secretion of the large intestine exceeds this volume, the excess will be excreted in the feces during diarrhea. As noted earlier in this chapter, cholera toxins and some other bacterial infections cause the crypts in the terminal ileum and colon to secrete 10 liters or more of fluid daily, resulting in severe and sometimes fatal diarrhea.