Small Bowel

Question 1

What is the ligament of Treitz?

Answer 1

A ligament that suspends the small bowel, separating the duodenum from the jejunum.

Question 2

What is the blood supply to the duodenum?

Answer 2

Proximal: gastroduodenal artery (from proper hepatic).
Distal: inferior pancreaticoduodenal artery (from SMA.

Question 3

What is the venous drainage of the duodenum?

Answer 3

Anterior, posterior pancreaticoduodenal vein (to SMV).

Question 4

What is the blood supply to the jejunum?

Answer 4

Branches of SMA.

Question 5

What is the blood supply to the ileum?

Answer 5

Branches of SMA.

Question 6

What is the lymphatic course from the small bowel?

Answer 6

1) Bowel wall
2) Mesenteric nodes
3) Lymph node channels parallel to SMV
4) Cisterna chyli
5) Thoracic duct
6) L subclavian vein

Question 7

What is the innervation of the small bowel?

Answer 7

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).

Question 8

What is the function of the enteric NS?

Answer 8

Neural control of all GI function: motility, blood flow, secretion, absorption.

Question 9

What are the differences between the blood supply of the jejunum and ileum?

Answer 9

Jejunum: few arcades, long vasa recta.
Ileum: many arcades, short vasa recta.

Question 10

What are the 3 major stages of digestion?

Answer 10

Intraluminal.
Intestinal (mucosal).
Transport.

Question 11

Describe the intraluminal stage of digestion.

Answer 11

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.

Question 12

Describe the intestinal stage of digestion.

Answer 12

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.

Question 13

Describe the transport stage of digestion.

Answer 13

Lymphatic transport of fats via the lacteals and portal system and transport of protein and carb breakdown products.

Question 14

What are MMCs?

Answer 14

MMC = Migrating Myoelectric Complexes.

Question 15

What is MALT?

Answer 15

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.

Question 16

Which aminosalicylates are used to treat Crohn’s disease?

Answer 16

Sulfasalazine.

5-ASA.

Question 17

Which immune modulators are used to treat Crohn’s disease?

Answer 17

Azathioprine.
Mercaptopurine.
Cyclosporine.

Question 18

What are indication for surgery in Crohn’s disease?

Answer 18

Obstruction.
Abscess.
Fistula.
Perforation.
Perianal disease.
Cancer.

Question 19

What is enteroclysis?

Answer 19

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.

Question 20

What is a Sonde enteroscopy?

Answer 20

An extended small bowel enteroscopy in which the enteroscope is advanced via peristalsis.

Question 21

What is the APUD system?

Answer 21

APUD = Amine Precursor Uptake and Decarboxylation.

Question 22

What is carcinoid syndrome?

Answer 22

Carcinoid tumor production of serotonin, bradykinin, tryptophan and exposure prior to breakdown in the liver.
Presents as cutaneous flushing, diarrhea, valvular lesions, bronchoconstriction.