Large intestine Flashcards
What does the large intestine consist of?
Colon Cecum Appendix Rectum Anal canal
What is the cecum? Where is it found?
It’s a blind pouch just distal to the ileocecal valve - larger in herbivores
What is the appendix?
A thin finger like extension of the cecum that is not physiologically relevant in humans
What are the functions of the colon?
- reabsorption of electrolytes and water
- elimination of undigested food and waste
What is the length and diameter of the colon?
1.5 m long
6cm diameter
Where is the ascending colon found?
Right side of the abdomen, runs from the cecum to the hepatic flexure (the turn of the colon by the liver)
Where is the transverse colon found?
Runs from the hepatic flexure to the splenic flexure (the turn of the colon by the spleen). Hangs off the stomach, attached by a wide band of tissue called the greater omentum (posterior side, mesocolon)
Where is the descending colon found?
From the splenic flexure to the sigmoid colon
Where is the sigmoid colon found?
From descending colon to the rectum - s shaped
Where is blood supplied from in the transverse colon?
Middle colic artery - branch of the superior mesenteric artery
What is blood from the distal third of the transverse colon perfused by?
Inferior mesenteric artery
What region of the colon is sensitive to ischemia?
The region between the distal third and the proximal transverse colon
What are the properties of the peritoneum?
- has fatty tags
- muscle coat has 3 thick longitudinal bands
- gut wall pouched in appearance
Where are the nodules of lymphoid tissue commonly found in the intestines?
- walls of distal small intestine (Peyer’s patches)
- large intestine (solitary nodules)
What is the suggested function of the appendices epiploica?
Protective function against intra-abdominal infections
What is necessary for large intestine motility?
Taenia coli
- three seperate longitudinal ribbons of smooth muscle that are shorter than small intestine
What are the formation of pouched ovoid segments called in taenia coli?
Haustra
How are Na+, Cl-, Water and K+ transported in colon?
Na+ and Cl- absorbed by exchange mechanisms and ion channels
Water follows by osmosis
K+ moves passively into lumen
What is the histology of the rectum?
Similar to colon but distinguished by transverse rectal folds in it’s submucosa and the absence of taenia coli in it’s muscularis externa
What is the terminal portion of the rectum called? What is it surrounded by?
Anal canal
Surrounded by internal circular muscle and external striated muscle anal sphincters
What cells are abundant in the large intestine?
Like the small intestine, enterocytes and goblet cells are abundant. Abundant crypts and stem cells are found in crypts
Where are mucosa found in the large intestine?
Mucosa appears smooth at gross level because no villi, smaller SA than small intestine
What kind of microvilli do enterocytes in the large intestine have?
Short, irregular microvilli and primarily concerned with resorption of salts
How is water absorbed in the large intestine? What is the result?
It passively follows electrocytes resulting in more solid gut contents
