A healthy intestinal mucosa plays an important role for the human body. If it is damaged, this can manifest itself in various symptoms and clinical pictures.
What is the intestinal mucosa?
The intestinal mucosa, also known as the mucosa, lines the intestine and is the innermost of four layers of the intestinal wall. The intestinal mucosa has a slightly different structure in each section of the intestine, adapting it to the different functions of the small intestine, large intestine, and rectum. It has important functions in digestion, protection against pathogens and for the immune system.
Anatomy and structure
The intestinal mucosa rests on a layer of connective tissue surrounded by smooth muscle. Between the intestinal mucosa and this musculature are nerve fibers. The intestinal mucosa is composed of three layers. It consists of a single-layered cylindrical epithelium, the lamina epithelialis mucosae. The cylinder epithelium is a specific form of epithelium, which takes its name from the elongated, cylindrical cells. The second layer is the so-called lamina propria mucosae, a connective tissue layer containing lymphatic and blood vessels as well as nerve fibers and immune cells. The third layer is a muscular layer called the lamina muscularis mucosae. This muscular layer is responsible for the intrinsic motility of the intestinal mucosa. The epithelial cells of the lamina epithelialis mucosae bear so-called microvilli, also known as brush border, which serve to increase the surface area. Due to the folded intestinal mucosa with the brush border of the lamina epithelialis mucosae, the surface area reaches approximately 200 square meters. The brush border is surrounded by a so-called glycocalyx to prevent self-digestion. The glycocalyx is composed of polysaccharides and is located on the outside of all cells. However, it differs between different cells in composition and structure, which determines its specific function. In addition to its main role in protecting against self-digestion, the glycocalyx of the intestinal mucosa is involved in the absorption of nutrients and contains digestive enzymes.
Function and Tasks
The main function of the intestinal mucosa is to absorb components from food and water. For this purpose, cells of the intestinal mucosa produce specific enzymes that cleave nutrients so that they can be absorbed and released into the blood. In this process, the absorption of the food components takes place either via active or passive resorption. In passive absorption, the food components come from the interior of the intestine, where they are present in high concentration, by osmosis into cells of the intestinal mucosa with a low concentration. In active absorption, the food components can also reach cells of the intestinal mucosa with an equally high or higher concentration of nutrients by consuming energy. The intestinal mucosa also protects against the invasion of harmful bacteria and parasites from food and the environment. It is colonized by numerous microorganisms beneficial to the body, known as intestinal flora. Approximately 400 to 500 different strains of bacteria are present in the healthy intestinal flora, but they only colonize after birth and are not yet present in the newborn baby. The intestinal flora prevents harmful microorganisms from colonizing the mucosa, modulates and stimulates the immune system, supplies the mucosa with nutrients and promotes metabolism. In addition, some bacterial strains of the intestinal flora produce important vitamins. The intestinal mucosa forms an important part of the immune system, as it contains more than 70 percent of antibody-producing cells of the body. It is therefore referred to as the gut-associated immune system. When pathogens invade, the antibodies bind to them so that the pathogens are recognized and destroyed by specific cells of the immune system. The immune system can distinguish between the bacteria of the healthy intestinal flora, food components and harmful substances or pathogens. Specific cells of the intestinal mucosa also produce various hormones that control the functions of the gastrointestinal tract.
Diseases and ailments
An unhealthy diet, taking medications such as antibiotics, cortisone or radiation or chemotherapy can throw the intestinal flora out of balance, as can taking painkillers over a long period of time, psychological strain and stress. If the intestinal flora is damaged over a longer period of time, this leads to changes in the intestinal mucosa and it becomes permeable to toxic substances or incompletely digested food components. Intestinal functions are disturbed and harmful germs can spread. If pathogens displace the beneficial microorganisms of the intestinal flora, this is referred to as dysbiosis or dysbacteria. Symptoms can manifest themselves in belching, flatulence, and even intestinal cramps or colic. Disturbances or damage to the intestinal mucosa can be the cause of many different clinical pictures due to its diverse functions. In addition to chronic inflammatory bowel diseases such as inflammation of the intestinal mucosa, Crohn’s disease or ulcerative colitis, allergies or weakened immune defenses can be the result. In Crohn’s disease, the inflammation can affect the entire digestive tract; in ulcerative colitis, the inflammation is limited to the colon and rectum. If only the appendix is affected by inflammation, it is appendicitis. Since untreated inflammation of the mucosa can lead to serious diseases such as colon cancer, symptoms should be taken seriously and a doctor consulted if necessary. Intake of pathogens via bad food or contaminated drinking water can lead to intestinal infections caused by pathogens that damage the intestinal mucosa. Classic symptoms are diarrhea, abdominal pain and loss of appetite. Triggers of particularly severe intestinal infections are, for example, typhoid and cholera pathogens. Another disease of the intestinal mucosa is celiac disease. Here, the mucosa of the small intestine has an intolerance to gluten, a grain protein.
