GI system: midgut and hindgut

Question 1

superior mesenteric artery syndrome

-cause

Answer 1

superior mesenteric artery crosses the third part of the duodenum anteriorly

• if the duodenum is compressed by a SMA aneurysm it can cause obstruction of the duodenum.
• additionally, can block left renal vein

Question 2

superior mesenteric artery syndrome

-clinical

Answer 2

• causes bilious vomiting in newborns (and adults?) which is curdled milk mixed with bile so it is greenish
• SMA may also compress left renal vein (nutcracker syndrome)
• may be relieved by patient leaning forward when eating

Question 3

congenital pyloric stenosis

-cause

Answer 3

-thickening of the smooth muscle of the pyloric sphincter.

Question 4

congenital pyloric stenosis

-clinical

Answer 4

• non-bilious, projectile vomiting (because obstruction proximal to bile duct)
• abdominal pain
• failure to gain weight
• dehydration

Question 5

annular pancreas

• what is it?
• problem

Answer 5

• the ventral pancreas may consist of two lobes
• if the lobes migrate around the duodenum in opposite directions to fuse with the dorsal bud, an annular pancreas is formed
• problem: forms ring around the duodenum which can cause an obstruction

Question 6

annular pancreas

-symptoms and signs in infants

Answer 6

• feeding intolerance
• bilious vomiting (curdled milk mixed with bile (greenish))
• —>therefore constriction usually occurs after sphincter of oddi
• abdominal distension

Question 7

annular pancreas

-symptoms and signs in adults

Answer 7

• abdominal pain, nausea, vomiting
• upper GI bleeding (from stomach ulceration)
• acute or chronic pancreatitis

Question 8

abnormalities of midgut rotation

-nonrotation

Answer 8

nonrotation:

• s.i. remains on the right side of the body
• ascending colon in the middle
• descending colon on the left

Question 9

abnormalities of midgut rotation

-mixed rotation and volvulus

Answer 9

mixed rotation and volvulus:

• accomplishes initial 90 degree rotation (counterclockwise; viewed ventrally)
• but second rotation of 180 degrees is in the opposite direction (clockwise)
• abnormal position of s.i. relative to L.I.

Question 10

abnormalities of midgut rotation

-subhepatic cecum and appendix

Answer 10

subhepatic cecum and appendix

• if have over-rotation of midgut during retraction (more than 180 degrees counterclockwise)
• results in cecum and appendix being abnormally placed in the upper right quadrant (instead of LRQ)
• in this case appendicitis can mimic biliary pain and present in the RUQ

Question 11

meckel’s diverticulum

-what?

Answer 11

-failure of vitelline duct (yolk stalk) to completely regress once midgut loop retracts into abdomen

Question 12

meckel’s diverticulum

-what can it cause?

Answer 12

omphalomesenteric cyst (omphalos means umbilicus)
-the fluid in the cyst can become inflamed and result in pain around the umbilicus (mimicking pain of appendicitis)

omphalomesenteric ligament (fibrous band)

• connects ileum to anterior abdominal wall
• can cause pain as well

Question 13

meckel’s diverticulum

-“syndrome of 2’s”

Answer 13

• 2% of population
• 2” long
• 2 feet proximal to ICJ
• 2 types of mucosa (gastric and intestinal)
• 2X more common in males
• 2% are asymptomatic

Question 14

McBurney’s Point

Answer 14

• location of the appendix

- 1/3 of the distance from ASIS to umbilicus (on right side)

Question 15

appendicitis

• definition
• cause

Answer 15

• obstruction of appendiceal lumen leads to inflammation and/or rupture
• cause of obstruction many times is a calcified appendicolith (old piece of stool)

Question 16

appendicitis

-clinical

Answer 16

• typically present with fever, nausea/vomiting and periumbilical/RLQ pain
• a ruptured appendix may lead to peritonitis

Question 17

peritonitis

-clinical

Answer 17

-inflammation of the parietal and visceral peritoneum

main manifestations:

• abdominal pain
• abdominal tenderness
• abdominal guarding

Question 18

diverticulosis/diverticulitis

• cause
• what?
• clinical

Answer 18

• due to low fiber diets
• outpouchings of the colonic mucosa and submucosa through weaknesses of muscle layers in the colon wall
• constipation (which increases intra-luminal pressure)

Question 19

colonic intussusception

-what?

Answer 19

• section of the bowel tunnels into an adjoining section, like a collapsible telescope
• may interrupt normal blood flow and cause necrosis

Question 20

colonic intussusception

-causes

Answer 20

• benign of malignant growths
• adhesions
• surgical scars
• motility disorders
• long term diarrhea

Question 21

ulcerative colitis

• what
• clinical

Answer 21

-chronic inflammation of the large intestine

clinical:

• diarrhea (sometimes with bleeding)
• pain
• weight loss
• inflammation of other organs

Question 22

whats the difference between crohn’s and ulcerative colitis?

Answer 22

crohn’s: can affect any area of the GI tract and is a segmented lesion

ulcerative colitis: only affects large intestine and is a continuous lesion

Question 23

what is the most common cancer of the GI tract?

Answer 23

-colon cancer

Question 24

where is the recto-sigmoid junction?

Answer 24

lies anterior to the S3 vertebra

Question 25

what are most cases of hemorrhoids caused by?

Answer 25

- not portal hypertension | - More often, hard stool or constipation causes increased pressure in rectum which compresses rectal veins

Question 26

rectouterine pouch (of Douglas) - where is it - significance

Answer 26

- space between uterus and rectum in females | - it is the lowest space in the pelvis of a female

Question 27

which two nerves supply parasympathetic innervation to the GI tract? How is the GI tract divided under their control?

Answer 27

- vagus supplies PNS innervation to foregut and midgut* - pelvis splanchnic nerves supply PNS innervation to the pelvis and hindgut* * Division is the boundary between the proximal 2/3 and distal 1/3 of the transverse colon

Question 28

hirschsprung's disease | -what?

Answer 28

-congenital absence of enteric parasympathetic ganglia in distal colon (ie, absence of enteric nervous system in distal colon)

Question 29

hirschsprung's disease | -clinical

Answer 29

- absence of peristalsis - dilation of proximal colon - constipation, failure to pass meconium, distension of the abdomen

Question 30

What landmark attaches to the first part of the duodenum

Answer 30

-the lesser omentum, specifically the hepatoduodenal ligament * the portal triad passes within the hepatoduodenal ligament * also the hepatoduodenal ligament forms the roof of the foramen of winslow (the only entrance to the lesser sac)

Question 31

What landmark attaches to the fourth part of the duodenum?

Answer 31

-the ligament of treitz * an extension of the right crus of the diaphragm * marks the transition between the duodenum (secondarily retroperitoneal) and the jejunum (intraperitoneal)

Question 32

What are plicae circulares? Where are they most concentrated?

Answer 32

- mucosal folds that extend across the entire diameter of the lumen - They are found throughout the small intestine but are most concentrated in the proximal jejunum

Question 33

Where are the highest number of arcades found? | Where are longer vasa recta found

Answer 33

Where are the highest number of arcades found? -distal ileum Where are longer vasa recta found? -proximal jejunum *The change between these two extremes is gradual

Question 34

Appendicitis presentations (3)?

Answer 34

1. periumbilical referred pain (lesser splanchnic) 2. RLQ somatic pain (subcostal T12) 3. psoas sign (pain upon hip extension)

Question 35

Where might an individual with a liver pathology experience referred pain?

Answer 35

- the right shoulder - The bare area of the liver is fused with the diaphragm - diaphragm innervated by phrenic nerve (C3,C4,C5)

Question 36

Where might an individual with a splenic pathology experience referred pain?

Answer 36

- the left shoulder | - in contact with the left portion of the diaphragm which is innervated by the phrenic nerve