The Villi Intestinal , In anatomy and physiology, Are those prolongations of the wall of the small intestine in which the absorption of food occurs.
These are special structures in which the nutrients that complement the function of the intestinal folds are assimilated. In fact, they are found within the same and function as transverse projections of the deeper cellular layers of the mucosa that reach up to 1 millimeter in length.
Much smaller than the intestinal villi are microvilli, which are also structures dedicated to the assimilation of nutrients.
In turn, microvilli are microscopic filaments that emerge from mucosal cells. Thanks to them and the intestinal villi, the absorption of food that is concentrated in the mucosal walls, multiplies thousands of times, since it takes full advantage of its surface.
In this way, the intestinal villi are extensions that cover the mucosa or lining that is in the small intestine. These are very tiny tubes of epithelium that have a large number of capillaries and which in turn rose a lymphatic vessel.
In its lower part, or base, the crypts of Lieberkühn are observed, which are glandular depressions that are in charge to realize the secretion of the enzymes that participate in the digestion of the intestines.
The absorption process is performed when the nutrients to be digested, which are in the form of carbohydrates and proteins, go to the portal vein by means of the capillaries that have the intestinal villi to pass later to the liver.
The lymphatic vessels are responsible for absorbing the fats that have been digested, so they do not go to the liver but to the bloodstream. In this cycle, the hormone secretin is present by the action of the mucosa of the small intestine.
As for their anatomical and physiological environment, these villi are respectively in the small intestine and in the later stages of digestion.
As curiosity, the villi are reminiscent of sea sponges, which sometimes make fingerings in which there are absorption cells, capillaries and lymphatic vessels. Therefore, all this structure is what allows these prolongations to fulfill their functions within the digestive system.
Anatomic-physiological context
After a meal or drink is ingested, the bolus is reduced in the stomach and traverses the small intestine.
The action of the enzymes is responsible for performing their chemical decomposition. It then goes through the intestinal tract, where it actually takes place the absorption of the nutrients that the body requires to grow, stay active and energized.
In this line, obtaining the nutrients occurs when some elements found in the small intestine have their share in the functions of the digestive system.
This intestine has two muscles (one circular and one longitudinal) and a membrane in which the intestinal villi are fixed, which share space with the microvilli and the folds of the intestines.
The organic fluids run constantly in their cavities and these contain various chemical substances but only those that have no utility go to the large intestine, where they are transformed into feces.
Thus, the intestinal villi form a microscopic structure that is inside a much larger structure, which extends for about six meters in length in the abdominal region.
On the other hand, in their physiological aspects, these villi are located in the final stages of digestion.
Structure and morphology
The intestinal villi, as mentioned, can be up to 1 millimeter in length, although this is not usually the norm because the size tends to be much smaller.
Its shape is similar to that of tiny projections that envelop and cover the mucosa of the small intestine, where most of the digestion takes place.
In this way, the coating covers a wide surface by its rolled design and above all by the existence of these villi.
Following criteria of space, the intestinal villi are tiny but numerous, which is why they are distributed throughout the small intestine.
This means that these villi have a passive role in digestion, since they do not move but are constantly being irrigated by the flow of nutrients that pass through the intestinal tract.
The food that has been consumed is moved by the rhythmic contractions that effect the muscular walls of the small intestine, although this one receives a chemical rain of secretions, enzymes and the bile.
However, the nutrients could not reach the liver or other parts of the organism without the contribution of intestinal villi which, because of its large distribution in the mucosa, allows its maximum use, since it touches them in its path.
In fact, intestinal villi can reach up to 25,000 per square inch, which equals about 40 per square millimeter.
Their number is greater at the beginning of the small intestine and is decreasing more and more as one advances in its journey, reason why its quantity is much smaller when they arrive at the borders that they adjoin with the large intestine. Viewed from a distance, the villi appear to be velvet.
On the other hand, in its outermost layer, the intestinal villi have absorption cells where the capillaries are and the lymphatic vessel that absorbs the fats.
Finally, above the villi is a layer of membrane, which has cells of various kinds in which the absorption of nutrients can go either to the blood or to the lymphatic system, with Goblet cells Which in the intestinal cavity secrete a mucous substance.
Additionally, the microvilli add up to 600 per cell of the epithelium, which explains why the small intestine has a potent ability to take food passing by.
Importance
Based on the above, the intestinal villi are extremely relevant in the human body because without them there would not be proper nutrition. Therefore, the person would be excreting what should serve to live well.
In this vein, intestinal villi do more than behave like marine sponges in the digestive system. They are the extensions that guarantee the entrance of the elements that impel the vitality of the organism.
Diseases
It is not always possible for intestinal villi to perform well. Occasionally, these can fail for causes that may be easy or difficult to determine, depending on the pathology that is being discussed.
Whatever the case, the truth is that there are circumstances in which these prolongations have clinical problems that can be diagnosed by the doctor; Problems that have as common denominator a malfunction of the digestive tract.
Thus, poor absorption of nutrients means that the small intestine is damaged, which makes it appear that the villi are not in good condition and therefore do not make an appropriate absorption of the nutrients that come with food.
An example is celiac disease, in which the mucosa of the small intestine has a condition in which there is no tolerance to gluten. In this link you can find the main Gluten free food For celiac.
References
- Abbas, B. and Hayes, T.L. (1989). Internal structure of the intestinal villus: morphological and morphometric observations at different levels of the mouse villus. Journal of Anatomy , 162, pp. 263-273.
- Abrahams, Peter H; Spratt, Jonathan D. Et al (2013). McMinn and Abrahams' Clinical Atlas of Human Anatomy, 7th edition. Amsterdam: Elsevier Health Sciences.
- Ball, Jane W., Stewart, Rosalin W. Et al (2011). Mosby's Guide to Physical Examination, 7th edition. Missouri: Mosby.
- Drake, Richard; Wayne Vogl, A. and Mitchell, Adam W.M. (2009). Gray's Anatomy for Students, 2nd edition. Amsterdam: Elsevier.
- Encyclopaedia Britannica (2016). Villus. London, United Kingdom: Encyclopædia Britannica, Inc. Recovered from britannica.com.
- Hall, John E. (2015). Guyton and Hall Textbook of Medical Physiology, 13th edition. Amsterdam: Elsevier Health Sciences.
- Hansen, John T. (2014). Netter's Clinical Anatomy, 3rd edition. Amsterdam: Elsevier Health Sciences.
- Palay, Sanford L. and Karlin, Leonard J. (1959). An Electron Microscopic Study of the Intestinal Villus. Journal of Cell Biology , 5 (3), pp. 363-371.