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Sigmoid Colon

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What is Sigmoid Colon?

The sigmoid colon is a part of the large intestine, the last section of the bowel, closest to the rectum and anus. It is a loop that resembles a Latin letter S or Greek letter sigma (ς). The length of sigmoid colon is around 40 centimetres, i.e., roughly a foot and a half long.

This part usually lies within the pelvis but can displace into the abdominal cavity due to freedom of movement. It comprises a set of muscle tissue arranged in two ways. Some bundles of muscle tissues, running up and down the length of the sigmoid colon, while some are arranged in annular bands around the tube. The annular bands pinch the tube shaping small sacs called haustra, making the sigmoid colon appear like a line of plethoric beads.

Sigmoid colon function is to hold faeces until you have the urge to use the bathroom. 


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Layers of Colon

There are four layers of colon, namely, mucosa, submucosa, muscularis, and serosa.

The mucosa membrane is the innermost layer of the colon and is made of mere columnar epithelial tissue. Its primary functions are to prevent the body from absorbing the bacteria present in the faecal matter and help the faeces waft through the tube.

The second layer of the colon is a sheet of connective tissue, nerves, and blood vessels called the submucosa. It supports other layers of the large intestine and absorbs the remaining nutrients present in the digested food.

The submucosa is surrounded by the muscular, the third layer of the colon, which contains multiple layers of visceral muscle cells that helps along the sigmoid tube in a process known as peristalsis.

The outermost layer of the colon, known as the serosa, is a smooth thin sheet of epithelial tissue. Its primary function is to secrete a watery fluid to keep the organ protected from frictional movement. 


Sigmoid Colon Function 

The primary sigmoid colon function is to act as a chamber that holds the faecal matter until it is expelled out of the body.

The slurry known as chyme passes through the ileocecal valve, and the cecum reaching the colon mixes with beneficial bacteria present there. It then flows through the four sections of the colon (haustra) over hours due to peristalsis. In some cases, this process can increase its speed by stronger waves of peristalsis that ensue a heavy meal.

If you think the only function of the sigmoid colon is to act as a chamber that holds faeces, you are highly mistaken. Though, maximum nutrients are already being absorbed in the small intestine and stomach before reaching the sigmoid colon. Sigmoid still plays a crucial role in absorbing vitamins from the faeces while it's waiting to be discharged.

These vitamins are necessary for good health and are produced by good bacteria present in the colon through fermentation and include:

  • Vitamin K

  • Biotin (vitamin B7)


Sigmoid Colon Problems

How is one supposed to know that one is having sigmoid colon problems? Well, you would probably feel sigmoid colon pain which is usually categorized as abdominal pain. Besides, one might also witness other symptoms such as nausea, loss of appetite, blood in stool, and might also experience constipation or diarrhoea. Besides these symptoms, some people suffering from sigmoid colon problems might also feel fatigued, lose weight and become anaemic. Now with an acquired knowledge about sigmoid colon pain and its general symptoms let's get into the depth and know what sigmoid colon problems can arise. 

  • Polyps

Polyps are masses of tissue occurring in the colon; although most are non-cancerous, late detection can turn them cancerous as they get bigger over time. Its occurrence isn't restricted to age but is most likely formed as you get older. Habitual smoking and overweighting can ignite its occurrence. 

  • Colorectal Cancer

Reports assert that colorectal cancer is the third most common cancer in the United States. 

Sigmoid colon cancer transpires when abnormal cells grow inside the colon tube, usually in polyps. If these cells are left untreated, they grow over time and develop from the inner layers of the colon into the walls of the organ and eventually into the blood vessels and lymph system.

Since early detection boosts the odds of recovery, it is advised to get regular colon screenings, especially if you are experiencing sigmoid colon cancer symptoms.

Some of the Most Common Sigmoid Colon Cancer Symptoms Are:

  • A resolute difference in your bowel practices, including constipation or diarrhoea or a change in the texture of the stool.

  • Persistent abdominal uneasiness (sigmoid colon pain), such as cramps or gas.

  • An uneasiness of not having a clean bowel. 

  • Rectal bleeding or witnessing blood in the stool.

  • Weakness or fatigue.

Besides Polyps and sigmoid colon cancer, several other sigmoid colon problems can arise, including ulcerative colitis, fistulae, volvulus, and more. Since each of them has a distinct impact, they require to be treated by a different specialist. Depending on the character of your colon problem, you could consult a gastroenterologist, a radiologist, an oncologist, or a colorectal surgeon.


Did You Know?

  • The four layers of the colon carry out different functions, and each has unique importance. 

  • The average length of the sigmoid colon is 25 to 40 cm, about one-fifteenth as tall as a Giraffe.

  • An estimate of 149500 Americans witnessed sigmoid colon cancer symptoms this year.

  • The sigmoid colon is also termed pelvic colon.

  • Despite lying within the pelvis, the sigmoid colon can displace into the abdominal cavity due to freedom of movement.

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FAQs on Sigmoid Colon

1. Where is sigmoid colon pain observed?

If you have a sigmoid colon problem, you're most likely to observe discomfort or pain in the lower region of the abdomen. You might also experience other symptoms like loss of appetite, abdominal bloating, blood in your stool, anaemia, or fatigue.

2. What is the principal function of the sigmoid colon?

The sigmoid colon, the concluding section of the large intestine that attaches the descending colon to the rectum, functions as a chamber that stores faecal wastes.