Large Intestine: Definition, Function, Diagram, Examples

The final portion of the digestive system is the large intestine, which absorbs water and salts from undigested food and forms solid waste. It consists of cecum, colon, rectum, and anal canal. It also lodges beneficial bacteria to facilitate fermentation and vitamins. This structure has a special role in eliminating waste and maintaining balance in the fluid content of the body. In this article, the Large Intestine, the structure of the large intestine, functions of the large intestine, large intestinal microbiota, common disorders of the large intestine, and treatment and management are discussed. Large Intestine is a topic of the chapter Digestion and Absorption in Biology.

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This Story also Contains

1. What is the Large Intestine?
2. Structure of Large Intestine
3. Functions of Large Intestine
4. Large Intestinal Microbiota
5. Common Disorders of the Large Intestine
6. Treatment and Management

What is the Large Intestine?

The large intestine is the last part of the digestive system in human beings and absorbs the remaining water and electrolytes from the undigested food particles. It consists of the cecum, colon, rectum, and anal canal. The large intestine plays an important role in forming and storing faeces until excretion. It also hosts gut bacteria in the lumen of the large intestine, which ferments undigested carbohydrates and produces vitamins like vitamin K. Similar to the small intestine, it does not absorb nutrients considerably. The large intestine regulates body hydration and proper removal of waste products, thus maintaining digestive health.

Structure of Large Intestine

It is further divided into :

Caecum

• It is the beginning of the large intestine.

• It is attached to the small intestine.

Colon

• Ascending Colon: Goes up the right side of the abdomen

• Transverse Colon: Crosses the abdomen from right to left.

• Descending Colon: Goes down the left side.

• Sigmoid Colon: This is an S-shaped segment that leads into the rectum.

Rectum

• The final part of the large intestine acts as a storage site for faeces before they are expelled.

Anal Canal

• This is the last part of the digestive tract through which the faeces are expelled.

Large Intestine Diagram

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Functions of Large Intestine

The large intestine carries out certain important functions like:

• Absorption of Water and Electrolytes: The reabsorption of water and key electrolytes from indigestible food matter.

• Formation and Storage of Feces: The waste is formed into solid stool and the process stores it until defecation.

• Microbial Fermentation: This system also contains bacteria that can ferment undigested carbohydrates to short-chain fatty acids.

• Vitamin Production: Certain intestinal microbes synthesise biologically essential Vitamins, such as Vitamin K and B vitamins.

Large Intestinal Microbiota

There is a huge diversity in the population of microorganisms in the large intestine:

• Types of Microorganisms Present: Representative bacteria, viruses, fungi, and protozoa.

• Role in Health and Disease: Beneficial bacteria work in digestion and immunity.

• On the contrary, any type of imbalance leads to diseases.

• Role in Metabolic Processes and Immunity: The gut microbiota influences metabolic processes and helps to protect against pathogens.

Common Disorders of the Large Intestine

Some common disorders of the large intestine are:

• Constipation: Difficulty in passing stools or infrequent bowel movements.

• Diarrhea: Frequent watery bowel movements.

• Irritable Bowel Syndrome (IBS): A chronic disorder characterised by abdominal pain and bloating, associated with changes in bowel habits.

• Inflammatory Bowel Disease (IBD): Represents Crohn's Disease and Ulcerative Colitis.

• These are conditions characterised by chronic inflammation of the gastrointestinal tract.

• Colorectal Cancer: Cancer that affects the colon or rectum. It is usually identified with screening tests.

Treatment and Management

Maintaining good health in the large intestine can be achieved in various ways:

• Dietary Changes: Increased intake of fibre, and water and avoidance of trigger foods.

• Medications: Laxatives in case of constipation, anti-diarrheal drugs in diarrhoea, anti-inflammatory in the inflamed lining of the intestine, and antibiotics in case of infection.

• Surgical Interventions: Surgery may be performed in severe conditions in which removal of diseased parts of the intestine is necessary.

• Probiotics and Prebiotics: Supplements for maintaining a healthy balance of gut bacteria.

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