Large Intestine

Structure
1. Characteristics
  1. Diameter – 2.5”
  2. Length – 3.5”
2. Location
  1. Mostly in abdominal cavity
  2. Part in pelvic cavity
3. Divisions
  1. Cecum – blind pouch from small intestine
    1. Appendix attached here
      1. No function in human
      2. Lower right abdominal quadrant
  2. Colon
    1. Ascending – begins at right iliac crest and moves toward liver
      1. Makes a 90* turn → hepatic flexure
    2. Transverse – begins at hepatic flexure and goes left to spleen
      1. Makes a 90* turn → splenic flexure
    3. Descending – begins at splenic flexure and goes to left iliac crest
    4. Sigmoid – “s” curve – from the descending colon to the rectum
  3. Rectum
    1. 7”-8” beyond sigmoid colon in pelvic cavity
  4. Anal canal – 1”
    1. From the rectum to the outside
    2. Sphincters
      1. Internal – smooth muscle – involuntary
      2. External – skeletal muscle – voluntary
Functions
1. Absorption
  1. Water
  2. Salts
  3. Vitamin K
  4. Vitamin B complex
  5. Vitamins produced by bacteria
2. Dehydration of feces
3. Defecation – elimination of solid wastes

Nursing Points

General

Tissue layers
1. Tunica serosa
  1. Serous membrane
  2. Visceral peritoneum
2. Tunica muscularis – smooth muscle
  1. Taenia coli – 3 strips of smooth muscle in colon (longitudinal)
    1. Shorter than whole intestine so it creates pouches
    2. Like elastic waistband
    3. Creates haustra
      1. Each haustra must fill with feces
  2. Inner circular muscle
3. Tunica submucosa – areolar CT
4. Tunica mucosa
  1. Simple columnar epithelium
  2. Goblet cells
  3. No villi present

References:

Betts, J.G., et al. (2017). Anatomy and physiology. Houston, TX: OpenStax, Rice University. Retrieved from https://openstax.org/details/books/anatomy-and-physiology?Book%20details

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Transcript

In this lesson we’re going to take a look at the large intestine.

The large intestine is a three and a half foot long, 2 and 1/2 inch diameter organ and it’s found mostly in the abdominal cavity and some in the pelvic cavity. It’s broken up into essentially four regions. You have the cecum, which is a pouch at the very very beginning of the small intestine. The appendix is actually attached to the cecum on the outside.

Then there’s the colon. It’s broken up into four divisions, the ascending, transverse, descending, and sigmoid. The ascending colon begins at the right iliac crest and moves upward towards the liver and then takes a 90-degree turn, and that’s called the hepatic flexure. The transverse colon begins at that hepatic flexure and goes all the way to the spleen, and then takes another 90-degree turn at the splenic flexure. The descending colon starts at the splenic flexure and goes all the way down to the left iliac crest. Right about there’s a sigmoid colon which is an s shaped organ and it’s the last part of the colon before it gets to the rectum. The rectum is then a 7 to 8 in Canal just beyond the sigmoid colon and it’s located in the pelvic cavity. Right after that is the anal canal which is a one inch canal and it runs from the rectum all the way to the outside of the body. It’s main controls are through sphincters. Sphincters are round muscle groups. There’s an internal, and an external sphincter. The internal sphincter is made of smooth muscle and is an involuntary process. Then there’s the external sphincter which is made of skeletal muscle and is a voluntary process.

Have a cold and has some really important functions. It’s mainly responsible for the absorption of water, salt, and a couple of different vitamins. These vitamins are vitamins K, and b12 and also those that are produced by bacteria.It’s also responsible for the dehydration of feces and the process of defecation which is the elimination of waste through the body.

Similarly to all of the other organs involved in the GI tract, the large intestine is made up of four different tissue layer. There’s the Tunica serosa, the Tunica muscularis, the Tunica submucosa, in the Tunica mucosa. The Tunica serosa is the most outer layer, and that actually attaches to the visceral peritoneum ended large intestine. The Tunica muscularis is really different in the large intestine. Running long ways down the large intestine is this strip of smooth muscle call the taenia coli, And it acts like an elastic waistband. It’s actually shorter than the entire length of the large intestine and because of that it creates these sac-like bulges called haustra. Each haustrum is important in the way that food moves down the large intestine. The haustrum has to fill with chyme and get enlarged and initiate a reflex and then it will squeeze and then propel the chyme to the next haustrum. That’s how chyme moves along the large intestine.

The Tunica submucosa is just a connective tissue between the Tunica mucosa and the Tunica muscularis. And the Tunica mucosa it’s made up of simple columnar epithelium and goblet cells which secrete mucus.
Okay so let’s recap.

The large intestine has four main divisions, the ascending, transverse, descending, and sigmoid colon. It also has a cecum, and appendix attached and includes the rectum and anus.

The large intestine is a primary location of water absorption and regulates the consistency of feces.

That to me a coli is the elastic waistband that creates the sac-like bulges in the large intestine called haustrum.

Remember those have to be filled each book before they moved to the next haustrum.
That’s it for our lesson on the large intestine. Make sure you check out all the resources attached to this lesson. Now, go out and be your best self today, and as always, happy nursing!