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Flashcards in small bowel Deck (47):
1

Gut embryology

https://www.youtube.com/watch?v=vJA1A0v6Aa4

2

Small intestine is derived from..?

Midgut. (With the exception of proximal duodenum, which is deriv from foregut)

3

Meckel's diverticulum is vestige of what?

Vitelline duct, which joins the yolk sac at the junction of the cranial and caudal limbs of the midgut limb

4

How long is the small bowel?

5-10 m (longest organ in GI tract)

5

Ligament of Treitz marks

Junction of duodenum and jejunum

6

Plicae circulares

Transverse mucosal folds in the lumen of the small bowell- present in distal duodenum and jejunum

7

Blood supply to duodenum

Proximal: gastroduodenal artery (off of proper hepatic artery-> branches into ant superior and post superior pancreaticoduodenal arteries).

Distal: inferior pancreaticoduodenal artery (off of SMA -> branches into ant inferior and post inferior pancreaticoduodenal arteries)

8

Venous drainage of duodenum

Ant and post pancreaticoduodenal veins -> SMV -> splenic vein + SMV = portal vein

9

Blood supply of jejunum and ileum

Branches of the SMA

10

Summary of small bowel blood supply

All of small bowel is supplied by branches of the SMA except the proximal duodenum, which is supplied by branches off the celiac trunk

11

Lymphatic drainage of small bowel

-> mesenteric nodes -> LN channels -> cisterna chyli (btw aorta and IVC) -> thoracic duct -> left subclavian vein

12

Innervation to small bowel

Sympathetic: vagus and celiac ganglia

Parasympathetic: plexus at base of SMA

Enteric NS: myenteric plexus = Meissner plexus (base of submucosa) and Auerbach plexus (in btw inner circumferential and outer longitudinal muscle layers)

13

What vessel is at risk of erosion/bleed if posterior duodenal bulb ulcer perfs?

Gastroduodenal artery

14

How to tell between jejunum and ileum?

Jejunum has few arcades with loong vasa recta, while ileum has many arcades with short vasa recta

15

Gastrin

Released in antrum. Stimulates gastric acid secretion and cell growth. Stimulated by vagus, food in Antrum, gastric distention, calcium. Inhibited by antrum pH

16

Cholecystokinin (CCK)

Released in the duodenum. Action is gallbladder contraction, inhibit gastric emptying. Stimulated by proteins and amino acids, fat, and acid. Inhibited by trypsin and chymotrypsin.

17

Secretin

Released in the duodenum. Action is to cause pancreas to stimulate bicarb, stimulates pepsin secretion, inhibits gastric acid secretion. Stimulated by low pH and duodenal fat. Inhibited by high duodenal pH.

18

Somatostatin

Released from pancreas. Action is to increase small bowel absorption of water and electrolytes, inhibits GI motility, secretion/action of all GI hormones. Stimulated by intraluminal fat, catecholamines. Inhibited by acetylcholine.

19

What is the clinical use of pancreatic polypeptide?

Only as a marker of other endocrine pancreatic tumors

20

Glucagon

Released in small bowel/colon. Action is to stimulate glycogenolysis, lipolysis, gluconeogenesis. Stimulated by low serum glucose. Inhibited by somatostatin.

21

Motilin

Action is to inhibit MMCs, increases gastric emptying, increases pepsin secretion. Stimulated by vagus, fat, alkaline duodenal environment. Inhibited by pancreatic polypeptide

22

MMCs

Migrating motor complexes aka migrating myoelectric complexes. Waves of electrical activity that sweep through intestines in a regular cycle while fasting, clearing non digestible along. These waves trigger peristaltic activity. Occurs every 90-120 min while fasting and is cause of stomach "grumbling" when hungry.

23

What are two things absorbed in ileum not absorbed elsewhere in small bowel?

Bile and b12

24

What is the most important immunoglobulin in the GI tract?

IgA

25

Age distribution of Crohns

Bi modal, 15-40 and 80 years

26

Risk factors for CD

Smoking, white race, northern location, Jewish, family history

27

Neoplasia of the small bowel can cause colicky abdominal pain by what mechanism?

Intermittent intussusception

28

Peutz-Jeghers syndrome

Hamartamatous polyps. Pigmented spots on lips.

29

Gardner syndrome

Colonic adenomas with increased risk of colon cancer. Autosomal dominant. Tumors: osteomas of skull, epidermoid cysts, fibroids, thyroid tumors.

30

What other types of benign tumors can occur in small bowel?

Hemangioma, fibroma, lipoma, leiomyoma

31

Two most common types of small bowel malignancies

Adenocarcinoma and carcinoid

32

Most common location for carcinoid tumor in the small bowel

Ileum

33

Carcinoid syndrome caused by what hormone excess?

Serotonin, tryptophan, or bradykinin. Can end up having pellagra because using so much niacin to make serotonin/tryptophan.

34

Other types of small bowel malignant tumors

Lymphoma, sarcoma, neuroendocrine, mets

35

Risk factors for lymphoma of small bowel

Celiac disease, immunosuppresion, autoimmune disease

36

Where is the most common site of carcinoid tumor overall?

Appendix (better prognosis)

37

What is the cell of origin in carcinoid tumors?

Enterochromaffin cell

38

Carcinoid syndrome usually occurs with appendiceal and small intestine carcinoid tumors only after what event?

Metastasis to the liver. This is because tumor is producing amines and peptides outside of the portovenous circulation.

39

How to treat fistula of small bowel

Consider somatostatin for high output fistulae, to decrease loss of fluids and electrolytes. IV antibiotics and bowel rest. If six weeks pass with no improvement resect tract and consider proximal ostomy if abscess found.

40

Small bowel obstruction (SBO) definition

Cessation, impairment, or reversal of transit of intestinal contents secondary to mechanical OR functional cause

41

Open loop SBO

Flow is blocked but proximal decompression possible

42

Closed loop obstruction

Inflow and outflow both blocked. Seen with incarcerated hernia, torsion, adhesions, volvulus. Requires emergent surgery

43

Most common causes of SBO

Extrinsic causes: adhesions, hernias, cancer

44

Other mechanical causes of SBO

Foreign body, gallstone ileus, intussusception. Crohns, lymphoma, radiation enteritis, abscess.

45

Functional causes of SBO (paralytic ileus)

Hypokalemia, peritonitis, ischemia, meds (opiates, anticholinergics), hemoperitoneum, retroperitoneal hematoma, postoperative, massive burn.

46

Management of SBO if patient is stable or has partial obstruction

IVF, NPO, NG tube decompression. Manage electrolytes and pain

47

Diagnosis and treatment of intussusception

Barium enema