Synonym
colon
Definition Colon
The colon is a part of the human digestive tract. It is located between the appendix (caecum, not to be confused with the appendix, which is only part of the appendix), which connects to the small intestine and ends before the rectum (rectum). The entire large intestine (including the caecum) has a length of about 1.
5 metres, the main part of which is the colon, which is divided into four sections. The ascending colon (Colon anscendens) is located in the right middle abdomen, followed by the transverse colon (Colon transversum), followed by the descending colon (Colon descendens), which is located in the left middle abdomen and merges into the sigmoid colon (Colon sigmoideum). Here the large intestine ends and flows into the rectum.
In its shape, the colon descendens encloses the small intestine like a frame open at the bottom. The colon has some morphological peculiarities (concerning its shape). These include the wrinkles visible from the inside (Plicae semilunares) which, when viewed from the outside, cause a constriction of the wall of the colon at regular intervals.
This results in bulges in the colon wall, so-called house walls. Further typical for the colon are its three outer longitudinal muscle strips, the so-called taenia. Each of the three muscle strips has its own name.
Thus one distinguishes: Fourth characteristic of the colon are its fat appendages (Appendices epiploicae). The inside of the colon is lined with mucosa, which is pervaded by crypts. The uppermost layer of the mucosa (epithelium) contains numerous goblet cells, which are responsible for the production of mucus.
The predominance of crypts over villi (mucous membrane protrusions) and the large number of goblet cells are microscopically typical for the colon. – Taenia libera
- Taenia mesocolica and
- Omental taenia
The ascending colon is mainly supplied by the arteria colica dextra (right colon artery), the transverse colon by the arteria colica media (middle colon artery). Both vessels originate from the arteria colica sinistra (left colon artery), which supplies blood to the descending colon, and the colon transversum through the arteria colica media (middle colon artery).
Often there is a connection between the flow areas of the superior mesenteric artery and the inferior mesenteric artery, which is called a riolan anastomosis. In the event of closure of one of the two visceral arteries, it ensures that the otherwise poorly perfused part of the colon is supplied with blood. If you are interested in this topic in more detail, you can find more information under Blood supply intestineThe nervous supply of the colon is provided by the vegetative (involuntary, i.e. not controllable) nervous system.
Roughly speaking, the sympathetic nervous system ensures reduced intestinal activity. It supplies the colon via the major and minor splanchnicus nerve (large and small intestinal nerve). The parasympathetic nervous system stimulates intestinal activity; it supplies the “front” (oral) part of the colon via branches of the vagus nerve, while the “rear” (aboral) part is supplied via the pelvic nerve.
The point at which this supply change takes place is called Cannon- point. It lies in the area of the left colonic flexure, i.e. the transition between the transverse colon and the descending colon. If you are interested in this, you can find more information under our topic:
- Sympathetic nervous system
- Parasympatheticus
The main function of the colon is to thicken the food.
Thus a strong water absorption takes place. The further transport of food by peristaltic waves is also one of the tasks of the colon. Important diseases that (partly) affect the colon are for example
- The chronic inflammatory intestinal diseases such as
- Ulcerative colitis
- Crohn’s disease
- Diverticulosis (numerous protuberances of the intestinal wall = diverticulosis, an inflammation of the diverticula is called diverticulitis)
- Colonic polyps (protrusions of the mucous membrane, which can occur sporadically or in large numbers, in which case one speaks of polyposis coli) and – as one of the most common types of cancer –
- Colorectal cancer (colorectal carcinoma), whereby the majority of tumors are not located in the colon (colon) but in the rectum. – Ulcerative colitis
- Crohn’s disease