Anatomy of the large intestine (colon)

2021-02-10 12:00 AM

With the exception of the specially shaped rectum, appendix, and anal canal, the rest of the large intestine has the following physical features that distinguish it from the small intestine.

The large intestine is the last segment of the digestive tract and is an inverted U-shaped. About 1.5 - 2 m long, connected to the ileum through the ileum by the ileocecal valve. Responsible for receiving indigestible foods (fibre...), some bacteria in the large intestine can produce vitamins for the body, absorb water and create faeces for excretion.

Figure. Colon

  1. Colon up 2. Appendix 3. Transverse colon 4. Transverse colon 4. Suspended colon 5. Down colon 6. Suspended colon 7. Sigmoid colon 8. Rectum

Large intestine segment

The large intestine consists of four parts:

The colon and appendix.

The colon is composed of the ascending colon, the transverse colon, the descending colon and the sigmoid colon


The anal canal and end are the anus.

 Outward appearance

With the exception of the specially shaped rectum, appendix, and anal canal, the rest of the large intestine has the following physical features that distinguish it from the small intestine.

Three longitudinal strips: go from the base of the appendix to the sigmoid colon.

Colonic aneurysm vesicles.

The conjunctival sac.

Location, shape and relevance of parts of the large intestine


Is the colon part located under the ileocecal valve, located in the right pelvic fossa, 6-7cm long and about 7cm in diameter?

Figure. The colon and appendix

1.Colon up 2. ileum 3. Appendix hole 4. Appendix 5. Colon


Worm-shaped is 3 to 13 cm long, originating from the inner edge of the cecum, where three longitudinal muscle bands meet. The appendix is ​​directed downwards, the lumen of the appendix connects to the lumen of the cecum with a hole in the appendix.


As the next part of the inverted U-shaped colon embracing the jejunum and ileum, it is divided into four segments.

Colon up: located on the right side of the abdominal cavity, stick to the posterior abdominal wall with the colon up. From the bottom up to the bottom of the liver, the angle bends to create the right angle of the liver or colon, connected to the horizontal colon.

Transverse colon: running from right to left, slightly upwards to below the spleen creating an angle or angle of the left colon. The transverse colon is attached to the posterior abdominal wall by a mesenteric membrane called the transverse conjunctival. The transverse colon mesenteric division divides the peritoneum into two layers, the upper layer of the transverse colon contains the hepatosplenomegaly and the lower layer of the transverse colonic mesenteric contains the ileum, ... Big goes from the large curvature to run down to cover the slopes - ileum then upwards clinging to the transverse colon.

Down colon: located on the left side of the abdomen. Just like on the right side, the down colon adheres firmly to the posterior abdominal wall with downward conjunctival. In the left pelvic fossa, the descending colon is followed by the sigmoid colon.

Sigmoid colon: Sigmoid-shaped, very variable in length, hanging on the posterior abdominal wall by the sigma.


The part of the colon located in the pelvic fossa, front of the sacrum, behind the bladder, prostate gland, and male seminal vesicles; uterus and vagina in women. About 15-20cm long, a bulging upper part called a rectal balloon, narrow lower part is the anal canal.

The rectum is structured like other parts of the colon, but there is no conjunctival sac or colonic aneurysm.

The peritoneum covers only the upper 2/3 of the rectum so there is a part of the rectum outside the peritoneum.

The muscle layer consists of the outer longitudinal muscle, the inner sphincter. The sphincter that thrives in the anus forms the inner sphincter, which is involuntary and is always in spasm, except when defecating. In addition, the anus also has an external sphincter, a striated layer formed by the anal lift muscle.

The submucosa contains blood vessels and nerves, often forming tangles, in which the tangles of veins are often dilated, causing haemorrhoids.

Figure. Rectum and anus

  1. The sphincter floor of the rectum 2. The longitudinal muscle 4. The anal lift 5. The external sphincter 6. The rectal lumen 7. Anal column 8. Anal sinus 9. Ligament 10. Anal valve 11. Anus 12. The comb area 13. The strategy

Mucosa: in the shadow of the rectum, it creates a semicircular fold, while in the anal canal the mucous layer is connected to the skin of the anus. The boundary in these two parts is the comb, above the mucosal comb that forms convex columns in the anal lumen, the anal column, the columns connecting at the base by mucosal folds are the anal valve. The space between the columns that form the vesicles is the anal sinuses, where the mouth poured in from the anal glands when an infection causes an abscess and is the cause of the anal fissure.

Colon blood vessels

Based on the embryo and blood vessels, the large intestine is divided into two parts right and left, where the boundary is the right 1/3 and 1/3 junction between the horizontal colon.

Right colon blood vessels

The artery nourishing the colon must consist of the lateral branches of the upper mesenteric artery, the median colon artery, the right colon artery and the ileo-artery.

Left colon blood vessels

The artery that nourishes the left colon arises from the lower mesenteric artery. The lower mesenteric artery is the branch of the abdominal aorta, running in the leaves of the left and sigmoid conjunctiva, ending with the upper rectal artery.

Along the way, the lower mesenteric artery for the lateral branches is the left colon artery connected to the median (or right colon artery) and the sigmoid artery.

In addition, the rectum and anal canal also receive blood from the middle and lower rectal artery, which comes from the inner pelvic artery.