Thin intestine
thin intestine it is the portion of that begins after and finishes in the blind person of . It is divided in three portions: duodeno, yeyuno e ileon.
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Function of the thin intestine:
The duodeno gathers the content of the stomach and it mixes it with secretions biliary and pancreática (in addition to own the duodenal one), taking it until yeyuno. The nutritional transit continues by this tube of about 6 meters (in the alive one) throughout which completes the process of the digestion and the absorption of the useful substances takes place. The phenomenon of the digestion and the absorption is going to depend greatly on the contact of with the intestinal walls, reason why whichever greater he is this one and in one more a ampler surface, as much better it will be the digestion and absorption of foods. This gives one us of the more important morphologic characteristics of the thin intestine that they are the presence of numerous you fold that they amplify the surface of absorption like:
- Fold circular.
- Intestinal Vellosidades (of 0.5 mm of height and an own lamina nucleus).
- Microvellosidades in the epithelial cells.
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Form and relations of the thin intestine:
The duodeno is characterized by its relation with the stomach, and páncreas, but yeyuno and íleon are more difficult to distinguish, and there is no a net separation between both.
In general, they are possible to be distinguished because:
- Yeyuno has greater diameter than íleon (3 centimeters yeyuno, 2 centimeters íleon).
- Yeyuno has more you fold circular, more intestinal vellosidades and finer, whereas íleon has less.
- However, in íleon the linfoides follicles (plates of Peyer) and the vascular irrigation in form of arches are greater, than in yeyuno. In addition their walls are thinner and less vascularizadas.
Topographically as much yeyuno as ileon occupies the infracólico space, although:
- Yeyuno above locates a little and to the left (umbilical region) that íleon (down and to the right).
- In general, the yeyunales handles are of more horizontal direction, whereas the ileales are of vertical direction.
The end of the thin intestine is íleon terminal that ends at the blind person by means of the ileocecal valve.
In the constitution of the intestinal wall, in addition to the usual layers of mucosa, submucosa, muscular and serosa, it emphasizes the presence of acúmulos of linfoide weave that reach to the submucosa. They are located in the antimesentérico edge and its number is of 30 or 40, and up to 2.5 cm of diameter. Since it has been mentioned previously, they are more numerous in íleon.
All the length of the thin intestine is united to the later wall through the root of mesenterio. This union of mesenterio to the later wall begins at level of L2, crosses the hook of the páncreas (by where it penetrates the superior mesentérica artery), it crosses in front of the inferior digging, it follows the ilíacos glasses common and external externally to finish in the right ilíaca grave, at level of the promontory, lateral to the right sacroilíaca joint, about 6 cm, of the mean line.
Arterial irrigation of the thin intestine:
The irrigation comes from the superior mesentérica artery, branch of the aorta, that walks within mesenterio and of which are born the arteries:
- Pancreáticoduodenales inferior. Soon it emits,
- Yeyunales branches and
- Ileales branches: Estos ramos yeyunales e of ileales tienen la particularidad de formar arcadas arteriales que SE anastomosan unas con otras. Arches of first order, new arches from these (of second order) and even of third order in íleon form. Finally, it originates
- Ileocólica artery, that ends up giving four branches: cólica a) ascending that raises by the ascending colon, b) cecal previous, c) cecal later, and the d) appendicular artery for the appendix. Other branches of the superior mesentérica artery leave towards the right angle of colon:
- Right Cólica and finally for the proximal part of the colon transverso
- The cólica artery average, that anastomosa with the previous one. Therefore, the superior mesentérica artery irrigates all yeyuno, íleon and right half of the heavy intestine including the appendix.
Venous drainage:
The venous drainage is enough similar, being the responsibility of the superior mesentérica vein, the main component of the vein carries, along with the inferior mesentérica vein and the esplénica vein.
Histología of the thin intestine
The intestinal mucosa is specialized in the digestion and the absorption of nutrients and for it must increase its surface that it gives to the light, of three ways:
- Fold circular, valves of Kerckring or plica, that are visible at first and are you fold permanent formed by mucosa and submucosa.
- Intestinal Vellosidades or villi, that has a size of 0.5 to 1 millimeter and gives the aterciopelada texture of the interior of the intestine.
- Criptas de Lieberkühn, that is located tubular glands between the vellosidades. At heart of of these criptas they appear the cells of Paneth.
Epitelio intestinal of the mucosa is formed by different cells that are:
- Absorbent cells or enterocitos: of these cells presents/displays in its luminal pole multiple microvellosidades that confer the aspect of border in brush to the optical microscope.
- Caliciformes cells: They are secretory of mucin.
- Cells endocrinas: They are cells argentafines, also calls cells of basal grains. They belong to system APUD.
- Cells indiferenciadas, responsible for the renovation.
- Cells of Paneth, that produces lisozimas, that is defensive, antibacterial.
The own lamina presents/displays a loose conectivo weave, with glasses and nerves. It is invaded by a linfocítica population and originating smooth muscular fibers of the muscular layer of the mucosa. Muscle of Brucke is denominated to him and is the motor muscle of the microvellosidades.
The lacteal conduit or quilífero power station is a central lymphatic glass of the microvellosidad. One is in all cross section of the microvellosidad. The coating of the quilífero is discontinuous.
Glicocálix is fundamental in the conclusion of the digestive process, as far as which it is the last link of the degradation. Of the absorbed elements, the fats go to the central quilífero, and the others to the blood.
If there are glands different from those from criptas, in the duodenal submucosa, we were in a duodeno, and if not in yeyuno íleon. The duodeno presents/displays these glands that secretan a mucin that neutralizes pH acid of quimo.
In the alimentary canal the presence of MALT, associated linfoide weave to mucosa is characteristic. This linfoide weave is in corion or own lamina of the mucosa. It is generally diffuse a linfoide weave or to nodular. Next to this linfoide weave are generally plasmocitos. In íleon the linfoide weave is specially well-known by its disposition in plates, denominated plates of Peyer. The lymphatic nodule produces a modification in epitelio of coating.
The glands of Brunner are the glands of the duodenal submucosa, that are characteristic of him.
The amount of caliciformes cells increases from the duodeno to the rectum, the absortivas cells diminish of duodeno to rectum. In the stomach there are no caliciformes cells, since own epitelio is mucígeno.
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Mouth - Pharynx - Esophagus - - Páncreas - Biliary vesicle - - Thin intestine (duodeno, yeyuno, íleon) - - Blind person - Rectum - Anus |
