The human digestive system, which includes the large intestine, is characterized by a variety of structures and functions of its various departments. This makes it difficult to diagnose digestive disorders, which affects the timeliness and effectiveness of therapeutic agents and methods. It is no secret that with the deterioration of the ecological environment, as well as with the irresponsible attitude of the person himself to his he alth, the number of gastroenterological diseases has increased in the world. They often become chronic, reducing the duration and quality of human life. This article is intended to explain in an accessible form the structure and functions of the human small and large intestines, as well as to acquaint you with the most common disorders in the work of these sections of the gastrointestinal tract.
General characteristics of the digestive system
Her work can be compared to a giant food processing factory, its splitting, assimilation and utilization of substances. Each section of the system has specificbiochemical reactions involving an arsenal of enzymes and biologically active substances, such as vitamins.
The large intestine, the structure and functions of which we are studying, is physiologically regarded as an organ involved in secretion, digestion, absorption and removal of substances from overlying sections. To understand the functions, first consider how the large intestine works.
Colon membranes
4 layers are clearly visible on histological preparations: mucous, submucosal, muscular and serous. They provide the main functions of the human colon: the formation of lymphocytes that play a protective role, the synthesis of B vitamins and vitamin K with the participation of beneficial bacterial flora, the production of mucus that improves the promotion of chyme. One of the most important functions of the large intestine is the absorption of water and solutions of organic and inorganic substances, leading to the formation of fecal masses from chyme.
Morphology of the large intestine
It has a length of up to 1.5 m and is divided into 6 parts: the caecum with appendix, the ascending, transverse, descending and sigmoid colons, as well as the rectum. The presence of three longitudinal muscle cords passing through the large intestine provides pendulum-like and perist altic contractions of its walls. On palpation, the colon is easily diagnosed, since their mucous membrane has the appearance of alternating expansions and narrowings. They are formed in those places where the circular muscles of the intestine are most pronounced. For a more completehighlighting the functions of the human large intestine, consider the features of its first section.
Cecum
Located in the right iliac part of the peritoneum, it has a length of 3 to 10 cm and looks like a bag. The appendix extends from the back. The walls of the caecum secrete enzymes, such as secretin, through which the chyme is digested. It also absorbs excess water.
The appendix contains micronodules that perform immune protective functions. It also actively develops beneficial microflora. The most common pathologies of the caecum include typhlitis, appendicitis, tumors and polyps.
Ascending and transverse colon
They are a continuation of the caecum and do not secrete digestive enzymes, but only participate in the absorption of water and s alt solutions. This leads to the compaction of the chyme and the formation of feces from it. The large intestine, whose functions primarily consist in the evacuation of undigested food debris, has bends: the right (hepatic) and the left (splenic), related to the transverse colon. Its functions are the production of mucus and the absorption of water and electrolytes. Diseases associated with the ascending colon include diverticulosis, polyposis, aganglionic megacolon (Hirschsprung disease), colitis.
The transverse colon is the longest. From above, it contacts the liver, gallbladder, spleen, and caudal pancreas. Its wallscontinue to secrete mucus and absorb water and mineral s alts.
Digestion in the large intestine
Carried out thanks to the enzymes of intestinal juice: cathepsin, peptidase, lipase, amylase. Their activity is about 200 times lower than that of the corresponding enzymes of the small intestine. That fact is extremely important. That for the processes of splitting in the large intestine, the presence of probiotics is necessary - groups of microorganisms that decompose fiber. These include bifidobacteria, lactobacilli.
In the large intestine, their total mass is 3-5 kg and is called the intestinal microflora. It enhances the secretion of intestinal juice, affects the protein-mineral metabolism, participates in the formation of immunity. The large intestine, whose functions we have named, is physiologically he althy if the processes of fermentation and putrefaction are balanced in its metabolism. As soon as the composition of the microflora changes (for example, due to malnutrition or as a result of drugs, especially antibiotics), putrefactive bacteria are activated and diseases arise: colitis, dysbacteriosis, dyspepsia.
Descending and sigmoid colon
In the area of the splenic flexure there is a section about 30 cm long, in which the processes of absorption of water and electrolytes and the promotion of feces continue. It is called the descending colon. At the location of the iliac crest is its part, which has the sphincter of Balli. Next, consider what is the function of the large intestine in the last part of the colon, calledsigmoid colon. She is partially mobile. If during its palpation rumbling is heard, it means that inflammation occurs in the sigmoid colon, accompanied by the accumulation of liquid contents and gases. In it, as in the transverse colon, there is often a decrease in peristalsis, which leads to the phenomenon of constipation - a spastic delay in defecation. It is in these departments that the large intestine, whose functions are the transport and evacuation of toxins, forms feces, which then enter the rectum.
Disorders of the sigmoid region have serious consequences for human he alth. With its inflammation (colitis or sigmoiditis), diarrhea and painful spasms in the left iliac part of the peritoneum are diagnosed. They are accompanied by bloating and belching. A physiologically normal decrease in pendulum and perist altic movements in the sigmoid colon can be complicated due to a sedentary lifestyle, improper diet, depleted in fiber and plant fibers. The result of these disorders is constipation, leading to intoxication of the whole organism. In the sigmoid colon, the formation of hernial sacs is possible - protrusions, leading to the development of diverticulosis. It is more common in the elderly, combined with irritable bowel syndrome. Its symptoms are alternating constipation and diarrhea, nausea, fever. The disease can be complicated by an abscess and is especially dangerous.
Rectum
She is the final section of the alimentary canal. Her dinais up to 15 cm. The large intestine, whose functions in this part of the gastrointestinal tract are to remove feces, ends with the anus and anus. The rectum has sphincters: the first on the border with the sigmoid colon, the next three are called proximal, internal and arbitrary external. All of them are involved in the physiologically normal process of defecation. The mucous layer of the rectum has folds with depressions called anal sinuses.
Between them and the anus there is an annular area - the hemorrhoidal zone. In it, thanks to the submucosal layer, slight stretching and displacement of the mucous membrane, densely braided with capillaries of the rectal arteries and veins, is possible. The superior rectal vein does not have valves, so its walls often expand - this leads to congestion and the appearance of hemorrhoidal bumps. The lymphatic system of the rectum is involved in immunity and prevents the spread of infection.
In this article, we studied the structure and main functions of the large intestine.
