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Colon. Venous drainage from the colon

The nervous system and the innervation of internal organs are perhaps one of the most complex areas of medicine. But knowledge of its basics, at least the bare minimum, will help in the future to better understand the activities of the genitourinary system and gastrointestinal tract, their pathology and diseases. Indeed, what mechanism, for example, moves food into the intestines? Who controls the processes of internal organs? From school years, each of us knows that the main organ is the central nervous system, i.e. the brain and spinal cord. But it turns out that the matter is not as simple as it seems at school. The central nervous system is precisely the central control apparatus, and there is also, as it is now fashionable to say in parliament, “local self-government,” i.e., an autonomous system for regulating the work of the internal organs of the human body. There are tens of millions of nerve cells in the gastrointestinal tract alone. Is it a lot or a little?

Of course, it’s not enough when compared with the 15-20 billion neurons of the brain. Even in modern physiology textbooks we find only a brief mention of these so-called intramural ("immured" in the walls of internal organs) neurons. However, morphologists have known about the existence of plexuses since the middle of the 19th century. They were found in a variety of organs, and most of all in the gastrointestinal tract, where they form a continuous multi-storey network along its entire length, starting from the esophagus and ending with the smooth muscles of the anus. Neurons are located here

groups, forming thickenings in this network - nerve nodules, or ganglia. The nervous system consists of the central nervous system (CNS) and the peripheral nervous system. The importance of the central nervous system is extremely great both for healthy people and especially for patients, which will be discussed repeatedly in the book. But in this case we will consider only the peripheral nervous system. It is divided into the somatic, which innervates the striated muscles and which “submits” to us (we can raise an arm, leg, turn our head), the sensitive nervous system (we feel heat, cold, touch, etc.) and, finally, the autonomic ( plant) nervous system, which innervates the internal organs, their smooth muscles and which “does not obey us” (we cannot force the stomach or intestines to move more strongly, etc.). In this case, we will be interested in the autonomic nervous system, which, in turn, is divided into sympathetic and parasympathetic. An important and very difficult point is the transmission of a signal from a nerve, a nerve ending to a muscle fiber, to a muscle and, in general, to a working organ. According to one hypothesis, an electrical potential of about 1 mV is created at the nerve ending, and as a result of complex processes, contraction of the muscle fiber and the entire muscle is observed. According to another hypothesis, a very small amount of a chemical substance is produced at the nerve ending - acetylcholine, which promotes the contraction of muscle fibers. It is interesting to note that acetylcholine is dissolved by alcohol; this is especially important to remember for big drinkers. This does not increase your strength over the years. Human blood is capable of inactivating acetylcholine at a temperature of 40 °C within 15 s. This may be the reason for the pronounced adynamia in patients with high fever. It should also be pointed out that the action of acetylcholine, released by nerve endings in the striated muscles, is immediate, strictly localized and extremely short-lived, which contributes to the ability of many musculoskeletal organs to perform fine movements (hands, vocal cords, tongue, etc.). On the contrary, in internal organs, including the smooth muscles of the intestines, the effect occurs more slowly, less localized and longer lasting.

Thus, nervous control over the smooth muscles of internal organs is less precise, slower, or, as physiologists say, more plastic than, for example, in striated muscles, which is explained by the peculiarity of the work of the ganglia described above.

There is a group of substances that potentiate and enhance the effect of acetylcholine. An increase in the amount of acetylcholine and substances that potentiate its effect is promoted by stress, nervous tension, despondency, etc. On the contrary, significant muscle work and physical activity help to destroy and utilize acetylcholine. Therefore, physical inactivity, constant nervous tension and stress are the cause of various spastic phenomena and intestinal dyskinesias.

Diseases of the digestive system,

The innervation of the colon is carried out by the branches of the superior and inferior mesenteric plexuses, as well as by the branches of the celiac plexus.

The nerve branches of the superior mesenteric plexus innervate the appendix, cecum, ascending colon and transverse colon. These branches approach the intestinal wall, located in the perivascular tissue of the main arterial trunks (a. ileocolica, a. colica dextra, a. colica media). Near the intestinal wall, they are divided into smaller branches that anastomose with each other.

1 - a. ileocolica; 2 - nerve branches of the plexus mesenterici superioris; 3 - ileum; 4 - a. appendicis vermiformis; 5 - appendix vermiformis; 6 - caecum.

The inferior mesenteric plexus is located in the perivascular tissue surrounding the artery of the same name, as well as at some distance from this artery. In some cases, the plexus consists of a large number of nodes connected to each other by internodal connections. In other cases, the plexus has two large nodes located on the inferior mesenteric artery (A. N. Maksimenkov).

The inferior mesenteric plexus has numerous connections with the celiac, renal, aortic and superior mesenteric plexuses. The nerves arising from these plexuses reach the intestinal wall either along the corresponding arterial trunks, or independently; they, like the nerves of the superior mesenteric plexus, are divided at the intestinal wall into smaller branches.

“Atlas of operations on the abdominal wall and abdominal organs” V.N. Voylenko, A.I. Medelyan, V.M. Omelchenko

The large intestine, intestinum crassum, begins in the right iliac fossa at the junction of the small intestine and ends at the anus. The total length of the large intestine is approximately 1.5 m. It has six sections: the cecum and the appendix; ascending colon; transverse colon; descending colon; sigmoid; rectum. General view of the large intestine 1 - ventriculus; 2 -...

The rectum, rectum, is the final section of the large intestine. Its upper border corresponds approximately to the II-III sacral vertebrae. The shape of the rectum depends on the degree of its filling. There is an ampullar shape, when the ampulla is well defined, and a cylindrical shape, if the ampulla is not pronounced. The rectum is divided into the ampullary part, ampulla recti, and the anal canal, canalis analis. Ampullary part...

Innervation of the left colon. 1 - colon transversum; 2 - nerve branches of the plexus mesenterici inferioris; 3 -a. colica sinistra; 4 - aa. sigmoideae; 5—colon descendens; 6 - nerve branches of the plexus mesenterici inferioris; 7 - colon sigmoideum; 8 - plexus mesentericus inferior; 9 - a. mesenterica inferior. The innervation of the rectum is carried out by branches going ...

The large intestine differs from the small intestine in certain characteristic features: The longitudinal muscles of the large intestine are concentrated in the form of three muscle bands, taenia coli, located along the entire intestine, starting from the base of the appendix to the rectum. There are free, mesenteric and omental bands. The free band, taenia libera, is located along the anterior wall of the cecum, ascending and descending colon; on the transverse...

The mucous membrane in the anal part of the intestine forms longitudinal folds in the form of rollers, columnae analis. These folds, moving downwards, thicken somewhat and connect with each other, forming a hemorrhoidal zone, zona haemorrhoidalis, in the submucosal layer of which the venous plexus is located. At the top of the rectal ampulla there is a fold of mucous membrane called the third sphincter. The mucous membrane of the emptied rectum...

The large intestine consists of the following sections:

  • cecum
  • colon
    • ascending colon
    • transverse colon
    • descending colon
    • sigmoid colon
  • rectum

Cecum

The large intestine includes the cecum, which in animals is usually quite large and always full. The mechanism of its filling is not well understood. When examining the large intestine of a hamster with X-rays, the passage of chyme through the sphincter with part of it entering the cecum was observed.

Bauhin's valve (ileocecal valve)

The large intestine is anatomically sharply separated from the ileum by a barrier in the form of either a strong ileocecal sphincter (in horses, donkeys), or in the form of ileocecal valves - bauhinium valves (in ruminants, pigs, carnivores and humans). Obviously, the passage of content through this barrier is somehow regulated. But little is known about this. It is only known that the wave of peristalsis does not pass from the jejunum to the large intestine and goes out at this barrier. It is also known that irritation of the splanchnic nerve, causing relaxation of the intestines, leads to contraction of the muscles associated with the valve.

Experiments on an isolated section of the intestine, consisting of a piece of colon with a valve, showed that the valve operates periodically and its opening and closing can be artificially caused by exposure to salts, acids, etc. in different concentrations. But it is hardly possible to completely transfer these observations to the whole organism. Recently, it has been established that in sheep the terminal portion of the ileum is functionally separate and plays the role of a sphincter that enhances the function of the valve.

The colon to the rectum is under the control of the vagus nerve, while the rectum is innervated by the last sections of the parasympathetic system from the sacral sections of the spinal cord.

In the large intestines, along with peristaltic movements that move the chyme to the anus, antiperistaltic contractions also occur, as a result of which the chyme moves in the opposite direction, and waves of peristalsis alternate with waves of antiperistalsis. In those places where there are taenia, i.e., longitudinal muscles are collected in ribbons, the taenia, with their contractions, shorten the intestine (in a horse, for example, two to three times) and collect the intestinal wall into pockets where chyme can lie for a long time in the form of dense pieces.

In the initial part of the large intestine, digestive processes are still finishing, in the final part - the rectum - feces are formed, and it is an excretion organ.

The digestive juice of the large intestines, due to the weakness of its enzymes, can hardly have any significance in the chemistry of digestion.

Microflora of the large intestine (bacteria)

The microflora of the large intestine plays a very important role in digestion, especially of fiber. It contains favorable conditions for the development of various types of bacteria that settle there from the first days of the animal’s life. They reproduce so intensively that, according to some estimates, they make up half (by weight) of all feces.

Carbohydrates, mainly fiber, undergo lactic acid, acetic acid, and butyric acid fermentation here.

Defecation

Defecation is a complex reflex. Feces irritate the mucous membrane of the last segments of the intestine, stimulation goes to the center of the act of defecation, located in the lumbar region of the spinal cord and, in response to irritation, two stimuli pass to the intestine: inhibitory to the sphincter of the anus and to the rectus muscles intestines - motor (Fig. 31). The abdominal press also participates in the act of expulsion of feces, which indicates the participation of the entire body in this process.

The large intestine (intestinum crassum) is a continuation of the small intestine and acts as the lower part of the digestive tract. The final stage of digestion occurs in the large intestine.

The human large intestine consists of the following sections:
- blind, on which there is also a vermiform appendix (appendix);

- colon, which, in turn, consists of the following sections:

Rising,

transverse,

descending,

and sigmoid colon intestines;

straight, consisting of an expanded part (rectal ampulla) and a narrowed part (anal canal), ending in the anus.

The large intestine originates from a short segment called the ileocecal valve. This segment is located immediately after the ileal outlet of the small intestine. A vermiform appendix branches off from the ileocecal valve - the appendix, the length of which is from 8 to 13 cm. Next, the cecum passes into the colon, which got its name due to the fact that it encircles the abdominal cavity. This is the longest section of the colon - its length is up to 1.5 m, and its diameter is 6 - 6.5 cm. The initial section of the colon is called the ascending colon, the following sections are called the transverse and descending colon. The colon is attached to the back of the peritoneum using a special peritoneal fold - the mesentery. The rectum ends in the anal canal. The anus is closed by the sphincter, which consists of striated and smooth muscles.

The inner part of the walls of the colon is lined with a mucous membrane, which facilitates the movement of feces and protects the intestinal walls from the destructive effects of digestive enzymes and mechanical damage. Thus, the structure of the large intestine is maximally adapted to the process of digesting food and removing unnecessary waste from the body.

Position (topography). The initial portion of the colon is located in the right iliac region. At this site, the final segment of the small intestine flows into it almost at a right angle. The cecum is located 4-5 cm above the center of the inguinal ligament. Below and to the left, loops of the ileum are adjacent to the cecum. The posterior surface of the ascending colon is adjacent to the fascia that covers the iliacus muscle and to the fascia of the right kidney. To the left and in front of the ascending colon are the greater omentum and loops of the small intestine. The transverse colon is located in the right hypochondrium, as well as in the epigastric region and in the left hypochondrium. Its middle part in some cases reaches the level of the navel or is even located below. In front, the transverse colon attaches to the anterior abdominal wall, but is separated from it by the greater omentum. In the upper part it is adjacent to the lower part of the liver, from below - to the loops of the small intestine, in the back - to the lowest part of the duodenum and to the pancreas. The descending colon in its upper part is adjacent to the anterior side of the left kidney.

Blood supply colon is carried out by various arterial vessels. Vessels from the superior mesenteric artery go to the right part of the colon, and vessels from the inferior mesenteric artery go to the left part of the colon. The final section of the colon, i.e., the rectum, is supplied with blood by arteries coming from the inferior mesenteric, internal iliac and internal pudendal arteries. The ileocolic artery departs from the superior mesenteric artery to the area of ​​the ileocecal angle. It goes from top to bottom, deviating to the right, and lies behind the peritoneum lining the posterior abdominal wall. The level of its origin is located 6-10 cm below the origin of the superior mesenteric artery.

Innervation is provided by the branches of the superior and inferior mesenteric plexuses and the branches of the celiac plexus. The nerve branches of the superior plexus innervate the appendix, cecum, ascending and transverse colon. Closer to the intestinal walls, the branches divide into smaller branches. Innervation of the rectum is provided by branches coming from the sacral section of the sympathetic trunk.

The most important functions of the large intestine are:

Digestive – processing of food bolus with enzymes. Enzymes extract water and nutrients from food (the process of reabsorption);

Muscular– increases (peristalsis increases when a new portion of food arrives) or reduces (at rest) the frequency of muscle contractions to move food masses;

Reservoir – accumulation and retention of feces, gases ;

Suction– useful and nutrients are absorbed in the ascending, blind and descending sections of the colon, from where they are distributed to all organs through the lymphatic and blood channels;

Protective– the mucous membrane protects the organ from destruction by digestive enzymes;

The colon removes toxic substances from the body;

Evacuation – removal of feces.

Innervation of the colon is provided by the superior and inferior celiac plexuses.

Right half of the colon is provided by nerves due to the solar plexus, which includes the vagus nerves, both celiac nerves, the superior ganglia and 2 inferior ganglia of the thoracic border of the sympathetic trunk. Numerous branches extend from the solar plexus to the internal organs, which in turn form plexuses along the blood vessels. At the origin of the superior mesenteric artery, the superior mesenteric nerve plexus (Plexus mesentericus superior) is formed, from which numerous nerve branches extend along the vessels to the small intestine, in particular to the terminal ileum and to the right half of the colon. Sympathetic fibers to the abdominal organs mainly come from the greater and lesser splanchnic nerves, and parasympathetic fibers from the vagus nerves. The fact of unequal distribution of portions of sympathetic and parasympathetic conductors for different parts of the digestive tract has been firmly established. Thus, in the area of ​​the appendix, in the cecum and in the ileocecal obturator apparatus, sympathetic conductors predominate. The vagus nerves increase tone and peristalsis, and irritation of the splanchnic nerves decreases the tone and peristalsis of the intestines. However, to date there is no consensus on the issue of intestinal innervation.

ation of the colon. In some cases, there may be unambiguous innervation from sympathetic and parasympathetic conductors. In such cases, motor and inhibitory impulses can travel along the same conductor, for example through the vagus nerve.

The closest sources of the nerve plexus for left half of the colon The inferior mesenteric and hypogastric nerve plexuses serve.
The inferior mesenteric nerve plexus is formed from nodal nerve clusters surrounding the initial section of the mesenteric artery. The inferior mesenteric plexus includes nerve branches from the left reno-aortic and superior mesenteric plexus, as well as branches from the superior (2) ganglia of the lumbar border sympathetic trunks.
From the inferior mesenteric plexus along the arterial trunks and in the spaces between them, numerous nerve branches extend fan-shaped to the splenic curvature, descending colon and sigmoid colon. Along their length, these nerve branches intertwine and, in turn, form a looping network of plexuses. At the level of the arterial arcade of the first order, nerve branches depart from the nerve plexuses, which enter the intestinal wall parallel to the blood and lymphatic vessels.

The hypogastric nerve plexuses, in addition to the nerve branches from the ganglia of the border trunk and branches from the inferior mesenteric plexus, include branches of the anterior roots of the II-III-IV sacral nerves, homologous to the branches of the vagus nerves. From the hypogastric plexuses ascending branches participate in the formation of the sigmoid plexus,
The intraorgan nervous apparatus of the colon is represented by the subserosal, muscular and submucosal nerve plexuses. The most pronounced nerve plexuses are in the submucosal and muscular layers, containing a large number of nerve
elements.
The intraorgan nerve plexuses of the colon are connected with each other and with the nerve branches entering the intestinal wall from the mesenteric nerve plexuses, and, in essence, are the peripheral part of the nervous system.