Large Intestine: Definition, Function, Diagram, Examples

What Is the Large Intestine?

The large intestine is the final part of the digestive system 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, 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.

Position and Extent of the Large Intestine

The position and extent of the large intestine is discussed below:

• Begins at the end of the small intestine

• Ends at the anal canal

• Surrounds the small intestine in the abdominal cavity

Structure of the Large Intestine

It is further divided into :

Caecum

• First part of the large intestine.

• 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

• Acts as a storage site for faeces before they are expelled.

• Needs Signal for defecation.

Anal Canal

• The last part of the digestive tract

• Faeces are expelled during defecation

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 Faeces

• 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

• 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.

Large Intestine NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Structure of Large Intestine

• Functions of Large Intestine

Practice Questions for NEET

Q1. The junction of ileum and large intestine is seen in the form of an orifice called

1. Peyer’s patch

2. Ileocolic

3. Plicae circulares

4. Hiatus

Correct answer: 2) Ileocolic

Explanation:

The sphincter muscle valve that controls the passage of waste from the small intestine to the large intestine is called the ileocecal orifice, sometimes referred to as the ileal orifice, ileocecal valve, or Bauhin valve.

Hence, the correct answer is option 1) The junction of the ileum and large intestine is seen in the form of an orifice called Ileocolic

Q2. Where do certain symbiotic microorganisms normally occur in the human body?

1. Oral lining and tongue surface

2. Vermiform appendix and rectum

3. Duodenum

4. Caecum

Correct answer: 1) Caecum

Explanation:

The cecum is a pouch-like structure located at the beginning of the large intestine, specifically at the junction of the small intestine and the colon. It is the first section of the colon and is involved in digestion. The caecum is a small blind sac that hosts some symbiotic micro-organisms. The appendix is a narrow finger-like projection attached to the caecum which contains beneficial symbiotic bacteria that helps in maintaining gut health.

Hence, the correct answer is option 4) Caecum.

Q3. Last section of large intestine is

1. Caecum

2. Colon

3. Rectum

4. Anus

Correct answer: 3) Rectum

Explanation:

The rectum is the final part of the large intestine, situated just before the anus. It plays a vital role in the elimination of waste from the body. The rectum stores formed faeces, which are the byproducts of digestion and absorption until they are ready to be expelled from the body during defecation.

Hence, the correct answer is option 3) Rectum

Also Read:

• MCQs on Large Intestine

• Pancreas Function in Human Body

• Digestion in Ruminants

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