Flashcards in Anatomy Of The Intestines Deck (67)
Microscopic structure of the small intestine?
Mucosa folded into villi
Villi separated by crypts
What happens when the cells of the small intestine epithelium reproduce and where do they do it?
Reproduce in the villi
Migrate towards the tips, maturing as they go
-acquire capacity to absorb
What do the microvilli do?
Massively increase the surface area to form a brush border
What does the brush border form?
An unstirred layer where nutrients meet and react with enzymes secreted by enterocytes (epithelial cells), completing digestion prior to absorption.
What are the main layers of the small intestine?
-with blood vessels, lymphatics and submucosal plexus
-2 smooth muscle layers, longitudinal and circular.
-Myenteric plexus lies between them
-loosely arranged fibroblasts
-vessels and nerves pass through it
Covered by mesothelium, commonly called serosa
What are enterocytes?
Columnar cells which contain brush border enzymes for digestion
What are goblet cells?
Exocrine glands which secrete mucin
What cells do the crypts of Lieberkuhn contain?
Stem cells - produce new cells
Enteroendocrine cells - synthesise and secrete hormones
Paneth cells - secrete protective agents
Peyer's patches (only in ileum)
Brunner's glands - secrete alkaline fluid to neutralise chyme
What protective agents do Paneth cells secrete?
Defensins and lysosyme
What do Peyer's patches do?
Contain MALT which house white blood cells and lymphocytes
Produce antibodies to protect from infection
Over all function of the large intestine?
Receives digested food from small intestine, from which it absorbs water and sodium to form faeces
Tell me about the cecum
First part of the colon
Blind ended sac
Slightly inferior to ileocecal junction
Can be palpated in right iliac fossa if enlarged due to poo/gas
Where is the appendix?
Attached to the posteriomedial end of caecum
Contains lymphoid tissue
What is the blood supply to the cecum?
Arterial: SMA -> ileocolic artery
Venous: ileocolic vein -> IMA
Where does the ascending colon extend from and to?
Cecum to right lobe of liver
Right colic flexure/hepatic flexure
Where does the transverse colon extend from and to?
Right colic flexure -> left colic flexure/splenic flexure
Where does the descending colon extend from and to?
Left colic flexure to the sigmoid colon
Where in relation to the left kidney is the descending colon?
Passes anteriorly to it over its lateral border
What marks the beginning of the sigmoid colon?
Where the descending colon turns medially
What structures are just posterior to the sigmoid colon?
Left common iliac artery
What is lateral to the ascending and descending colon? Function?
Left and right paracolic gutters
Drain any fluid that leaks from the colon
Clinical relevance of the paracolic gutters?
Allow any potentially infectious material to circulate around the peritoneal cavity which can cause further infection
This is how a ruptured appendix can cause peritonitis
Arterial and venous supplies to the ascending colon?
Arterial - ileocolic and right colic branches of SMA
Venous - ileocolic and right colic tributaries of SMV
Blood supply of the transverse colon?
Arterial - middle colic of SMA
Venous - SMV
Blood supply of descending colon?
Arterial: Left colic and superior sigmoid - branches of IMA
Venous - IMV
Blood supply of sigmoidal colon?
Arterial: sigmoid arteries - branches of IMA
Which artery forms an anastamosis between the superior and inferior mesenteric arteries?
Clinical relevance of the colonic blood supply?
It is collateral, so maintains blood supply in case of occlusion/stenosis of one of the major arteries.
Where is the rectus located?
Begins at S3
Immediately anterior to sacrum