Esica, or sigmoid colon, is a fragment of the lower digestive tract. Esica is an inseparable part of the large intestine, which plays a key role in the transport of fecal content, the absorption of water and minerals, and even regulates the functions of the central nervous system and the immune system.

Esica-sigmoid colon(Latinsigmoideum ) is a fragment of the large intestine, to which also include the cecum, appendix, colon, rectum, anal canal. The above division of individual sections of the large intestine is not associated with systematic differences, but is based on a different topography and different attitudes of their mesentery. Topographically, the descending colon passes into the sigmoid colon at the level of the iliac crest, and at the level of the second and third sacral vertebrae, the sigmoid colon passes into the rectum.

Esica - construction

The division of the colon looks like this:

  • ascending colon
  • transverse colon
  • descending colon
  • sigmoid colon

The length of the colon can vary between 15 cm and 90 cm, but on average it is 40 cm. Esica has the shape of a horizontally arranged letter S. The distinguishing feature of the colon is its mesentery, thanks to which it has great mobility. The shape and position of the colon vary depending on the length of the colon, the length of the mesentery, the level of filling of the bladder and rectum, the size of the uterus of a pregnant woman.

When the pelvic organs enlarge, the sigmoid colon rises upwards. Filled with fecal content or gases, it also falls out of the pelvis and may occupy a number of different locations, e.g. the top of the loop may be located in the iliac fossa, in the umbilical region, it may reach the transverse colon, or even the visceral surface of the right lobe of the liver or the greater curvature of the stomach.

An interesting fact from the field of physiology is thatthe newborn's sigmoid colon , which produces only one loop, is heavily filled with meconium and does not fit into the relatively small pelvis. through which it reaches to the right iliac fossa.

The wall of the sigmoid colon has a four-layer structure, characteristic of the gastrointestinal tract. It consists of:

  • mucosa
  • submucosa
  • muscle membrane
  • serous membrane

The inner surface of the intestine is lined with a single-layer cylindrical epithelium. The mucosa has numerous intestinal crypts that are longer than that of the small intestine. The crypt wall is made of:

  • cylindrical (absorptive) cells
  • goblet cells
  • stem cells
  • enteroendocrine cells
  • Paneth cells

The epithelial cellsfrom the crypts move to the surface of the intestine, where they form the lining epithelium, the cells of which gradually exfoliate. In the mucosa and in the submucosa there is locatedgut associated lymphoid tissue - GALT , consisting of single endothelial lymphocytes, connective tissue lymphocytes and lymph nodes.

Muscle membraneis arranged in two layers: inner - circular, well-developed and outer - elongated, shaped in the form of three longitudinally running smooth myocytes, called bands of the colon. The characteristic structure of the wall in the form of bulges of the colon and crescent folds is caused by the tension of the above-mentioned bands of the colon.

The feature that distinguishes the large intestine from the small intestine isno villi , which are protrusions of the mucosa, which increases the lymphatic area of ​​the intestine 8 times. Their number in the small intestine is approximately 90 million.

Esica - functions

  • Absorption of mineral s alts and water- thanks to this function, the food content is compacted, which allows to maintain a proper water and osmolal balance. Under extreme conditions, the intestine can recover up to 6 liters of water per day.
  • Mucus secretion- it is transported to the lumen of the intestine, which gives the appropriate consistency of the digestive content and facilitates its excretion
  • Stool formation
  • Bacterial flora- bacteria that are located in the large intestine are specialized in the production of vitamin B12 (essential vitamin for the process of erythrocytopoiesis) and vitamin K (needed for the synthesis of coagulation factors)
  • Due to the presence of the intestinal flora specific to the intestinethey inhibit the growth of "bad" bacteria,which can cause various diseases
  • The gut-brain axis- bacteria in the gut produce specific chemicals that regulate the functions of the central nervous system, e.g. microbiota dysbiosis may be associated with increased inflammation the body, irritable bowel syndrome,and even depression

What is intestinal peristalsis?

The intestines contract and relax with the aid of smooth muscles. Earlier it was mentioned that there are two types of the muscle layer, i.e. the longitudinal layer, which is responsible for the shortening movements of the intestines, and the circular layer leading to the narrowing of the intestines. These movements spread along the length of the intestine and are called perist altic movements.

How is the muscle cells stimulated and the bowel moving as a result? The contraction of the muscle cells of both layers is ensured by pacemaker cells called interstitial cells (Cajala). These cells are located between both muscle layers and generate cyclic high-amplitude depolarization waves that spread to the muscle cells of both layers.

There is a Meissner nerve plexus in the submucosa and an Auerbach plexus in the muscular membrane, these structures can be called the intestinal nervous system as it regulates and excites some bowel movements. In these plexuses there are motor and sensory neurons and neurons that connect other neurons.

These neurons are responsible for triggering local reflexes. Sensory neurons collect information about the quality and quantity of food content, and connecting neurons mediate the transmission of this information to motor neurons. These neurons, together with the Cajal cells, lead to shortening and contraction movements, and thus to the passage of chyme along the intestine. An interesting fact is that in the entire gut, the number of neurons is greater than the number of neurons in the spinal cord.

Major diseases of the sigmoid colon

The most common pathology of the sigmoid colon isdiverticulitis . Diverticula are small hernias of the mucosa that are pushed out along with the submucosa through the wall of the large intestine in places of reduced resistance. There are pseudo-diverticula and true diverticula, the former do not have a muscle layer, while true diverticula contain all layers of the intestine.

The main factor responsible for the development of diverticula is a diet low in plant fibers, impaired motor function of the intestine, low physical activity, stress, consumption of highly processed products. The major complication of diverticular disease is diverticulitis ( diverticulitis ) and massive diverticulitis.

Diverticulitisis formed when the intestinal mucosa is damaged by food debris in the diverticula, which leads to inflammation within the diverticulum, and then in the pericolic fat, in the mesentery and the surrounding wall bowels. Complicationdiverticulitis is:

  • intestinal abscess
  • mechanical obstruction
  • diffuse peritonitis
  • colo-bullous fistulas

Diverticulitis manifests:

  • pressure soreness of the lower abdomen on the left side
  • painful diarrhea
  • constipation
  • fever
  • thin people feel a hard, tense sigmoid colon

Laboratory tests show leukocytosis, increased ESR and CRP.

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Category:

Anatomy