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.
FAQs on Sigmoid Colon
1. What is the sigmoid colon and where is it located in the human body?
The sigmoid colon is the S-shaped final section of the large intestine, connecting the descending colon to the rectum. It is approximately 35-40 cm long and typically resides within the pelvis, though its flexibility allows it to sometimes move into the abdominal cavity. Its name comes from the Greek letter sigma (ς), which it resembles.
2. What are the primary functions of the sigmoid colon?
The main function of the sigmoid colon is to act as a storage chamber for faeces before they are eliminated from the body through defecation. While most nutrient absorption occurs earlier in the digestive tract, the sigmoid colon also plays a role in absorbing residual water, electrolytes, and certain vitamins (like Vitamin K and Biotin) produced by beneficial gut bacteria.
3. What are the different layers that make up the wall of the sigmoid colon?
The wall of the sigmoid colon, like the rest of the colon, is composed of four distinct layers. From innermost to outermost, these are:
- Mucosa: The innermost layer that secretes mucus to help faeces pass smoothly and protects the body from bacteria.
- Submucosa: A layer of connective tissue, blood vessels, and nerves that supports the other layers.
- Muscularis: A muscle layer that contracts in a wave-like motion called peristalsis to move stool along the colon.
- Serosa: The thin, outermost layer that secretes a watery fluid to prevent friction with other organs.
4. How does the function of the sigmoid colon differ from other parts of the large intestine?
While the entire large intestine is involved in absorbing water and electrolytes, its different sections have specialised roles. The ascending and transverse colons are primarily responsible for absorbing the majority of water and forming stool. In contrast, the sigmoid colon's main role is storage. It acts as a final holding area, allowing for the voluntary control of defecation, whereas the other sections are more focused on the continuous process of chyme dehydration.
5. Why is the sigmoid colon S-shaped, and what advantage does this shape provide?
The S-shape of the sigmoid colon is an anatomical adaptation that serves two key purposes. Firstly, it allows this section of the intestine to fit within the crowded space of the bony pelvis. Secondly, the curves provide extra length and expandability, enabling it to accommodate and store a variable amount of faecal matter before a bowel movement is initiated. This shape also helps to slow down the final passage of stool, aiding in the regulation of defecation.
6. What are some common problems that can affect the sigmoid colon?
Several conditions can affect the sigmoid colon. Common issues include:
- Diverticulosis: The formation of small pouches in the colon wall that can become inflamed (diverticulitis).
- Polyps: Tissue growths that are often benign but can become cancerous over time.
- Colorectal Cancer: The growth of malignant cells, which can arise from untreated polyps.
- Volvulus: A rare but serious condition where the sigmoid colon twists on itself, causing an obstruction.
7. Can a person live without a sigmoid colon?
Yes, a person can live without a sigmoid colon. The surgical removal of this section is called a sigmoidectomy or sigmoid colectomy. This procedure is typically performed to treat conditions like colorectal cancer, severe diverticulitis, or a volvulus. After removal, the surgeon usually connects the end of the descending colon directly to the rectum. While digestion and nutrient absorption are largely unaffected, patients may experience some changes in bowel frequency or consistency as their body adapts.
