Synonyms in a broader sense
Colon, Interstitium grassum, colon, rectum, rectum (rectum, rectum), appendix (caecum), appendix (Appenedix vermiformis)
Definition
As the last digestive tract section, the large intestine connects to the small intestine and frames the small intestine with its 1.5 meters length from almost all sides. The main task of the large intestine is to extract (absorb) the liquid and various minerals (electrolytes) from the food in the intestinal contents and thus thicken the stool. The large intestine is colonized by bacteria (microflora), which perform important functions for the large intestine and thus for the organism.
The large intestine begins behind the Bauhin’s valve (ileocecal valve), which shields the small intestine from the bacteria colonized colon. Behind it lies the appendix (cecum, caecum), which, as the name already describes, ends blind in the abdominal cavity. The appendix is about 7 cm long and has a projection, which is also called appendix vermiformis because of its appearance.
The appendix vermiformis is 9 cm long on average, but its length is subject to strong individual variations. The position of the appendix is very variable, which is why appendicitis does not always appear immediately. The length of the entire colon also varies.
The length of the colon varies from person to person. For example, age, sex, genetic disposition and height play a role. Roughly speaking, a normal human colon is between 1.20 and 1.50 meters long.
The individual sections also differ in length: In the right half of the abdomen lies the ascending colon (ascending colon), which is about 20-25 cm long. At the level between the 12th thoracic vertebral body and the 2nd lumbar vertebral body, the approximately 40cm long colon transversum (horizontal colon) runs horizontally to the left side. This is followed by the descending colon (descending colon) at 20-25cm, which merges into the sigmoid colon (s-shaped colon) at about 40cm.
Thus the colon forms a frame around the much longer small intestine (about 3.75m). Furthermore, the small appendix with the appendix appendix and the rectum, which is about 15-20 cm long, are part of the large intestine. There are certain structures that are particularly characteristic of the large intestine.
The macroscopically visible, colon-specific taenia, are three approx. 1 cm wide longitudinal stripes, on which the longitudinal muscles are somewhat compressed. The so-called housetren are also typical for the macroscopic appearance of the colon.
They are created by periodic contractions of the ring muscles, so that constrictions can be distinguished from bulges at intervals of a few cm. Also typical for the large intestine (colon) are fat appendages (Appendices epiploicae), which hang down from the taenia. For the enlargement of the surface there are crypts (Glandulae inetstinales) in the colon, which are 0.5 cm deep and close together.
For this purpose, the villi, which are typical for the small intestine, are no longer needed in the large intestine for food absorption. In addition, the colon is characterized by many goblet cells and particularly long microvilli, which represent the micro relief of the mucosa. The wall structure of the mucosa of the large intestine corresponds as far as possible to that of the other sections of the digestive tract.
- From the inside, the colon wall is lined by mucosa (tunica mucosa), which is divided into three sublayers. The uppermost layer is a covering tissue (Lamina epithelialis mucosae, epithelium). The epithelium of the colon contains a particularly large number of cells, which are filled with mucus that they periodically release into the intestinal tract, thus ensuring the gliding of the intestinal contents.
These are called goblet cells. The next sublayer is a shifting layer (Lamina propria mucosae), which contains a particularly large number of lymphocytes and lymph follicles for the defense function of the intestine. Then comes a very narrow layer of the patient’s own muscles (lamina muscularis mucosae), which can change the relief of the mucosa.
- This is followed by a loose shifting layer (Tela submucosa), which consists of connective tissue and in which a network of blood and lymph vessels runs, as well as a nerve fiber plexus called the plexus submucosus (Meissen plexus).
This plexus represents the so-called enteric nervous system and innervates (regulates intestinal activity) the intestine independently of the central nervous system (CNS).
- The next layer of colon muscle (tunica muscularis) is divided into two sublayers, each of which has fibers running in different directions: First, an inner circular stratum (stratum circulare), which forms the typical intestinal ducts (see above) through periodic contractions.The outer longitudinal muscle layer (stratum longitudinale) is somewhat compressed at the so-called tenens (see above). Between this ring and longitudinal muscle layer runs a nerve fiber network, the plexus myentericus (Auerbach plexus), which innervates these muscle layers. This musculature is responsible for the wave-like movement of the intestine (peristaltic movement).
- This is followed by another shifting layer (Tela subserosa).
- The end is a coating of the peritoneum which lines all organs. This coating is also called tunica serosa.
- Thyroid cartilage larynx
- Trachea (windpipe)
- Heart (Cor)
- Stomach (Gaster)
- Large intestine (colon)
- Rectum (rectum)
- Small intestine (ilium, jejunum)
- Liver (Hepar)
- Lung
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