Large Intestine (Colon) - Diagram

A major portion of the large intestine is made of the colon. The large intestine in humans is made up of the following parts:

  1. Cecum with an appendix
  2. Ascending colon
  3. Transverse colon
  4. Descending colon
  5. Sigmoid colon or pelvic colon
  6. Rectum
  7. Anal canal

Let’s learn more about the structure of the large intestine with a well-labelled diagram.

Table of Contents:

Well-labelled Diagram of Large Intestine

Large Intestine Diagram

Large Intestine – Description

  • The large intestine is a 1.5 m long organ that extends from the ileocaecal junction to the anus.
  • It constitutes the cecum with an appendix, ascending colon, transverse colon, descending colon, pelvic or sigmoid colon, rectum and the anal canal.
  • Caecum is a large blind sac-like structure that forms the commencement of the large intestine. The vermiform appendix is a worm-like diverticulum that arises from the posteromedial wall of the caecum.
  • The ascending colon is about 12.5 cm long, and it extends from the caecum to the inferior surface of the right lobe of the liver.
  • The transverse colon is about 50 cm long, and it extends across the abdomen from the right colic (hepatic) flexure to the left colic (splenic) flexure.
  • The hepatic flexure lies at the junction of the ascending and transverse colons. It lies on the lower part of the right kidney. The splenic flexure lies at the junction of the transverse and descending colon. It lies on the lower part of the left kidney, below the anterior end of the spleen.
  • The descending colon is about 25 cm long, and it extends from the splenic flexure to the sigmoid colon. It is narrower than the ascending colon.
  • The sigmoid or pelvic colon is about 37.5 cm long and extends from the pelvic brim to the third piece of the sacrum, where it becomes the rectum.
  • The anal canal is present below the level of the pelvic floor, and it connects the rectum to the anus.
  • The large intestinal wall is formed by four layers – the serosa layer, muscularis layer, submucosa layer and the mucosa layer.
  • The serosa layer is formed by the peritoneum of the abdominal wall.
  • The smooth muscles of the large intestine make the muscularis layer. The longitudinal muscle fibres of the large intestine are arranged as three long bands called taenia coli. The length of the taenia coli is less when compared to the length of the large intestine. Because of this, the large intestine is made into a series of pouches termed haustra.
  • The submucosal layer is not well developed in the large intestine. The mucosal layer has the mucous-secreting glands but lacks villi that are present in the mucous membrane of the small intestine.

Significance

The structures of the large intestine are adapted for storage of matter reaching it from the small intestines and for absorption of fluid and solutes from it. Also, adequate lubrication for the passage of its content is provided by the goblet cells scattered in the mucous membrane. The solitary lymphatic follicles of the large intestine provide protection against microbes present in the lumen of the intestine.

Frequently Asked Questions

What are the main regions of the large intestine?

The large intestine is a 1.5 m long structure that forms the last part of the digestive system. The major regions of the large intestine are the caecum, colon, rectum and anal canal.

What are the three main divisions of the small intestine?

The three major parts of the small intestine are the duodenum, jejunum and ileum. The ileocecal valve is a sphincter that separates the small and the large intestines.

What is the main role of the large intestine?

The major role of the large intestine is to absorb water and electrolytes from the indigested food and moves the waste matter toward the anus.

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