Small Bowel Flashcards
What is the ligament of Treitz?
A ligament that suspends the small bowel, separating the duodenum from the jejunum.
What is the blood supply to the duodenum?
Proximal: gastroduodenal artery (from proper hepatic).
Distal: inferior pancreaticoduodenal artery (from SMA.
What is the venous drainage of the duodenum?
Anterior, posterior pancreaticoduodenal vein (to SMV).
What is the blood supply to the jejunum?
Branches of SMA.
What is the blood supply to the ileum?
Branches of SMA.
What is the lymphatic course from the small bowel?
1) Bowel wall
2) Mesenteric nodes
3) Lymph node channels parallel to SMV
4) Cisterna chyli
5) Thoracic duct
6) L subclavian vein
What is the innervation of the small bowel?
Parasympathetic: fibers from vagus and celiac ganglia.
Sympathetic: fibers from ganglia in plexus at base of SMA.
Enteric NS: myenteric plexus (Meissner plexus at base of submucosa and Auerbach plexus between inner circumferential and outer longitudinal layers of muscle wall).
What is the function of the enteric NS?
Neural control of all GI function: motility, blood flow, secretion, absorption.
What are the differences between the blood supply of the jejunum and ileum?
Jejunum: few arcades, long vasa recta.
Ileum: many arcades, short vasa recta.
What are the 3 major stages of digestion?
Intraluminal.
Intestinal (mucosal).
Transport.
Describe the intraluminal stage of digestion.
Prepares ingested nutrients for absorption.
1) Hydrolysis of food by salivary, pancreatic, and gastric enzymes.
2) Fats and fat-soluble enzymes are hydrolyzed by bile salts.
3) Fatty acids and monoglycerides form micelles, facilitating uptake at brush border.
Describe the intestinal stage of digestion.
Final digestion of carbs and proteins and absorption of nutrients by epithelial cells.
1) Carbs hydrolyzed by brush border oligosaccharidases and disaccharidases.
2) Peptides hydrolyzed by brush border and intracellular peptidases.
3) Enterokinase activates trypsinogen to trypsin, which converts many other pancreatic enzymes to their active form.
Describe the transport stage of digestion.
Lymphatic transport of fats via the lacteals and portal system and transport of protein and carb breakdown products.
What are MMCs?
MMC = Migrating Myoelectric Complexes.
What is MALT?
MALT = Mucosa-Associated Lymphoid Tissue.
Comprised of lymphoid nodules, mucosal lymphocytes, isolated lymphoid follicles in the appendix and mesenteric lymph nodes.
Predominately in small bowel and colon.
Which aminosalicylates are used to treat Crohn’s disease?
Sulfasalazine.
5-ASA.
Which immune modulators are used to treat Crohn’s disease?
Azathioprine.
Mercaptopurine.
Cyclosporine.
What are indication for surgery in Crohn’s disease?
Obstruction. Abscess. Fistula. Perforation. Perianal disease. Cancer.
What is enteroclysis?
Double-contrast study that involves passing a tube into the proximal small bowel and injecting barium and methylcellulose.
Detects tumors missed by conventional small bowel follow-through.
What is a Sonde enteroscopy?
An extended small bowel enteroscopy in which the enteroscope is advanced via peristalsis.
What is the APUD system?
APUD = Amine Precursor Uptake and Decarboxylation.
What is carcinoid syndrome?
Carcinoid tumor production of serotonin, bradykinin, tryptophan and exposure prior to breakdown in the liver.
Presents as cutaneous flushing, diarrhea, valvular lesions, bronchoconstriction.
