Large Intestine Flashcards
What makes up the large intestines?
Caecum Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Anal canal
What epithelium lines the large intestines?
Columnar epithelium
What are the roles of the large intestines?
Removes water from indigestible gut contents
Production of some vitamins
Temporary storage
Is the ascending colon intra or retro peritoneal?
Retroperitoneal
Is the transverse colon intra or retroperitoneal?
Intraperitoneal - has its own mesentery = transverse mesocolon
Is the descending colon intra or retroperitoneal?
Retroperitoneal
Is the sigmoid colon intra or retroperitoneal?
Intraperitoneal - has its own mesentery
Is the rectum intra or retroperitoneal?
Upper 1/3 - intraperitoneal
Middle 1/3 - retroperitoneal
Lower 1/3 - no peritoneum
What is the arterial supply to the midgut?
Superior mesenteric artery
What are the branches of the SMA?
Jejunal arteries Ileal arteries Ileo-colic artery Right colic artery Middle colic artery
What do the jejunal arteries supply?
Jejunum
What do the ileal arteries supply?
Ileum
What does the ileo-colic artery supply?
Caecum
What does the right colic artery supply?
Ascending colon
What does the middle colic artery supply?
Transverse colon
What is the arterial supply to the hindgut?
Inferior mesenteric artery
What are the branches of the IMA?
Left colic artery
Sigmoid arteries
Superior rectal artery
What does the left colic artery supply?
Descending colon
What do the sigmoid arteries supply?
Descending colon
Sigmoid colon
What does the superior rectal artery supply?
Upper 1/3 rectum
What is the venous drainage of the midgut?
Superior mesenteric vein
What is the venous drainage of the hindgut?
Inferior mesenteric vein
What is the venous drainage of the rectum?
Upper 1/3 - superior rectal vein -> IMV
Middle/lower 2/3 - systemic venous system
What is the difference in the muscle of large intestine compared to the small intestine?
External longitudinal muscle is incomplete
What are teniae coli?
Three distinct bands of smooth muscle on the large intestines
What are haustra?
Sacculations caused by contraction of the teniae coli
How is water absorbed in the large intestines?
Facilitated by ENaC
Tighter tight junctions - creates bigger gradient so more water absorbed
What induces water absorption in the large intestines?
Aldosterone
What is inflammatory bowel disease?
Group of conditions characterised by idiopathic inflammation of the GI tract
What are the 2 main conditions in IBD?
Crohn’s disease
Ulcerative colitis
Where can Crohn’s affect?
Anywhere in GI tract - commonly ileum
How thick is the inflammation in Crohn’s?
Transmural
Is Crohn’s inflammation continuous?
No -skip lesions
What are the gross pathological features of Crohn’s?
Skip lesions Hyperaemia Mucosal oedema Cobblestone appearance Fistulae
What are the microscopic pathological features of Crohn’s?
Granuloma formation
Where can UC affect?
Begins in rectum
How thick is the inflammation in UC?
Mucosa only
Is UC continuous inflammation?
Yes
What are the pathological changes in UC?
Crypt abscesses
Reduced number of goblet cells
Pseudopolyps
Loss of haustra
What is the potential sign of Crohn’s on a barium follow through?
String sign of kantour
