Index
The human body has two types of intestines.
The first one is connected to the stomach, called the small intestine, and operates as the middle part of the digestion process of food. And the final part of the digestion process is called the large intestine. It is a large tube that escorts waste from the body.
The colon is an inverted, U-shaped part. The colon is part of the large intestine and extends between the cecum.
The colon can be easily recognized through several morphological features, such as semilunar folds and haustra bags.
Histologically, the mucosa is lined by a simple columnar epithelium and contains crypts of Lieberkuhn and numerous goblet cells.
Anatomy
Parts of the colon
The colon is the longest part of the large intestine. It starts from the cecum at the ileocecal valve and ends at the rectum.
The colon frames the convolute of the small intestine in the abdominal cavity.
However, it can be shortened and quite flexible in the event of incomplete rotation of the umbilical loop during embryogenesis.
The colon can be subdivided into four parts: ascending, transverse, descending, and sigmoid colon.
The ascending colon lies secondary retroperitoneally on the right side of the abdominal cavity and moves to the right colic flexure on the lower side of the liver.
The transverse colon moves intraperitoneally to the spleen, forming the left colic angle.
This part is attached to the posterior abdominal wall by the mesocolon and is therefore very flexible.
Beginning at the left colic flexure, the descending colon proceeds retroperitoneally down the left abdominal wall and changes to the S-shaped sigmoid colon in the left iliac fossa.
Because the sigmoid colon lies intraperitoneally, it also has a mesocolon.
This last part of the colon ends in the rectum at S2 and S3.
Structure of the colon
The colon is made up of several layers, from the inside to the outside:
- A mucosa without a valve.
- A highly vascularized and innervated submucosa.
- Circular (internal) and longitudinal (external) smooth muscle.
- A serous envelope (peritoneum).
Morphological characteristics
Macroscopically, the colon has different morphological characteristics compared to the small intestine.
The semilunar folds arise on the inner surface through muscular contractions. These are functionally caused and therefore movable. These folds form pockets on the outer surface (haustra).
Macroscopically, the colon has different morphological characteristics compared to the small intestine.
The longitudinal musculature is concentrated in three strong ribbon-like strips (taeniae coli).
The mesocolon joins the mesocolic tapeworm and the greater omentum to the omental tapeworm, while the free (or liberal) tapeworm is accessible and fully visible.
Another characteristic of the colon is the small fat-filled sacculation formed by the serosa (appendages epiploicae).
Blood supply
Branches of the superior mesenteric artery (right colic artery, middle colic artery, and colic branch of the ileocolic artery) supply the ascending and transverse colon.
The descending colon and the sigmoid colon are supplied by branches of the inferior mesenteric artery (left colic artery and sigmoid arteries).
The left and middle colic arteries form Riolan’s (inconstant) anastomosis.
Venous blood drains through the veins corresponding to the superior and inferior mesenteric veins.
Innervation
Up to the Cannon-Boehm point in the left colic angle, the sympathetic innervation is carried by the nerves of the superior mesenteric plexus. In contrast, the vagus nerve carries parasympathetic innervation (cranial nerve X).
After that point, the inferior mesenteric plexus nerves carry the sympathetic innervation, and the pelvic splanchnic nerves have the parasympathetic innervation.
Histology
The colon has the typical histological structure of the digestive tract: mucosa, submucosa, muscular, and serious, adventitial.
The mucosa is lined with long microvilli with a simple columnar epithelium (epithelial lamina).
It is covered by a layer of mucus that helps transport stool.
The mucosa does not contain villi but rather many crypts of Lieberkuhn in which numerous goblet cells and enteroendocrine cells are found.
The connective tissue layer (mucosa of the lamina propria) is filled with macrophages, plasma cells, and other immune cells.
The submucosa comprises blood vessels, lymph nodes, and particularly fatty tissue.
The internal circular musculature of the muscular is strongly pronounced, while the external longitudinal musculature is found practically only in tapeworms.
Function
The main task of the colon is the temporary storage and transport of stool.
The function of the colon is to eliminate the remains of food from which the nutrients have already been extracted; it also removes bacteria and other wastes from the body’s metabolism.
This process is called intestinal peristalsis and lasts approximately 36 hours.
In this way, it absorbs about 1 liter of water daily, which leads to thickening of the stool.
In addition, it absorbs sodium, potassium, and chloride, but it can also secrete potassium.
The intestinal physiological flora is rich in anaerobic bacteria (approximately 1011 per gram) that live in symbiosis with the human body.
They fulfill other essential functions such as the breakdown of indigestible food ingredients (e.g., cellulose), the production of vitamin K, and the support of the immune system.
Also called the large intestine, the colon follows the small intestine and forms the last part of the digestive system. It consists of several components:
- The cecum (from which the vermiform appendix emerges).
- The ascending colon (right).
- The transverse colon.
- The descending colon (left).
- The sigmoid colon.
- The rectum.
Its function is mainly to eliminate waste, absorb water, maintain water balance and absorb specific vitamins.
The chyle from the small intestine lacks almost all (90%) of the nutrient already absorbed by the digestive system.
Chyle mixes with mucus and intestinal bacteria in the colon to form fecal material.
The bacteria that digest the fibers form new molecules that the colon can assimilate.
The pH is between 4.5 and 7.5. The first things that are eliminated as they pass through the colon are liquids and salt.
The waste then reaches the sigmoid, where it is stored.
Later, when the body is ready to defecate, the waste is expelled through the rectum.
Size
The colon is more exhaustive than the small intestine but also shorter.
The small intestine is approximately 6.7 meters long and 4 to 8 centimeters in diameter.
Colon diseases
The colon, also known as the large intestine, is part of the digestive system.
It is a long, hollow tube at the end of your digestive tract where the body makes and stores stool.
Many disorders affect the colon’s ability to function correctly.
Diseases that are generally associated with the colon are:
Colorectal cancer
This type of cancer starts in the colon or near the rectum (lower colon).
One of the most common causes of death is associated with cancer.
Colonic polyps
They represent an abnormal growth of tissue located in the inner lining of the colon or rectum.
Polyps are benign and non-cancerous growths. However, they can sometimes become cancerous.
Polyps can be adenomatous, which can turn into cancer.
And hyperplastic and inflammatory polyps.
Colon dysplasia
Dysplasia is cells in the colon lining that look abnormal under a microscope.
These cells are generally not cancerous, but they can turn into cancer cells.
Colon dysplasia can develop in people who have had illnesses such as ulcerative colitis or Crohn’s disease for many years.
The spastic colon
This condition is also known as irritable bowel; it is more than a colon problem.
They are spontaneous contractions or loss of movement in the muscles of the small and large intestines.
Ulcerative colitis
They are ulcers that appear in the colon and rectum.
Diverticulitis
Diverticulitis is an inflammation or infection that occurs in the bags of the colon.
Prevention
It would help if you ate a healthy diet high in fruits and vegetables, rich in fiber, drank adequate water, and regular exercise to promote good colon health.
Supplements such as curcumin and omega-3s can help reduce inflammation.
It may also be helpful to take vitamins such as vitamin B6.
Colon cleansing
It is common for people to use colon cleansing substances to maintain a healthy colon.
This process includes the administration of laxatives, tea, supplements, enemas, or colon hydrotherapy to remove waste from the colon.
When cleaning is done, it can have side effects, and some of these methods can even be dangerous.
Treatment of diseases in the colon will vary depending on the condition and severity.
Treatment generally includes a healthy diet, medications, and surgery in some more severe cases.
