Intestinal mucosa - intestinal villi

"Intestinal mucosa

Overall, one of the most important functions of the Galeazzi's glands (crypts) is to secrete a liquid, called enteric juice, which is rich in water, electrolytes, mucus and digestive enzymes. Among the digestive components we remember the "enterokinase, which activates pancreatic trypsinogen in trypsin (essential for the digestion of proteins), lactase (which breaks down lactose into glucose and galactose) and other enzymes, called disaccharidase, responsible for the digestion of disaccharides.

The enteric juice, which is filamentous due to the presence of mucus, adheres tightly to the microvilli and its presence is essential in the final phase of digestion and in the subsequent absorption of nutrients

In the lamina propria, in addition to the connective tissue, there are lymphocytes, granulocytes and lymphoid tissue (sometimes grouped in nodules called Peyer's plaques), which on the whole defend the organism from foreign agents.

One of the main characteristics of enterocytes is that they live only a few days. As they age, these cells detach from the villus, pass into the intestinal lumen and are eliminated in the faeces. The cell population renewal process is continuous and the cleaved enterocytes are promptly replaced by new cells migrated from the crypts. As they rise towards the top, the enterocytes mature, age and, when they reach their apex, break up. The peculiar phenomenon of cell migration means that every three to five days the enterocyte population is completely replaced by new cells. This rapid and continuous renewal has the purpose of keeping the digestive and absorbing efficiency of the intestine high. Unfortunately, as happens for other types of epithelium, the high speed of multiplication and replacement of cells increases the susceptibility to cancer; that to the colon, in particular, represents one of the leading causes of death in Western countries.

The presence of the villi makes it possible to fivefold the absorbent surface of the intestine, a function to which they are used in the first person. Inside each villous a dense network of capillaries flows, essential for the transfer of nutrients from the intestinal lumen to the bloodstream. At the center of this vascular mesh there is a lymphatic vessel called central chilifer of the villus, which is also important for distributing the absorbed substances to the various parts of the organism. In particular, while water, mineral salts, carbohydrates, water-soluble vitamins and amino acids pass directly into the vascular network of the villus, fatty acids, cholesterol, other lipids and fat-soluble vitamins flow into the lymphatic vessel.

The large intestine mainly performs a function of reabsorption of water from the fluid mass coming from the small intestine (kilo) and promotes the expulsion of waste through peristaltic movements. It is devoid of villi but retains the Lieberkuhn crypts, consisting of two types of cells: the absorbent ones in the most luminal portion and the goblet-shaped ones; the former, unlike the latter, tend to decrease towards the rectum. At the base of the crypts there are regeneration cells and enteroendocrine cells used for hormonal secretion.

The functionality and health of the intestinal mucosa can be undermined by various diseases, such as celiac disease, giardiasis and Crohn's disease.