GI Anatomy Review Flashcards
The gut is a tube within a tube which travels from the oropharangeal membrane to the membrane.
cloacal
3 developmental regions of the gut are supplied by 3 paired/unpaired arterial branches
unpaired (which is unique)
What are the 3 unpaired arterial branches that supply the gut and which part of the gut do they suppy?
- Foregut- Celiac Trunk
- Midgut- Superior Mesenteric
- Hindgut-Inferior Mesenteric
What is unique about the spleen developmentally as compared to the other organs of the digestive system?
originated de novo from the mesogastrium and not a gut tube derivative
The celiac trunk supplies the foregut which includes the :
Esophagus, stomach, proximal duodenum, pancreas, liver, gallbladder, spleen*
The midgut supplied by the superior mesenteric artery supplies which organs?
Distal duodenum, jejunum, ileum, cecum, appendix, ascending colon, 2/3 transverse colon
The hindgut, supplied by the inferior mesenteric artery, contains which organs:
Distal 1/3 transverse colon, descending colon, sigmoid colon, rectum
Which organs are retroperitoneal (without a mesentery and associated with the posterior abdominal wall)?
aorta, inferior vena cava, kidneys, and suprarenal glands
Which organs are secondarily retroperitoneal (organs which had a mesentary once and lost it during development)?
duodenum (descending, horizontal and ascending), colon (ascending and descending), pancreas, rectum (upper 2/3)
A 44-year-old male presents to the ED with fever and back pain. He is later diagnosed with a retroperitoneal infection. Which of the following structures is most likely to be affected?
A. Body of stomach
B. Sigmoid colon
C. Proximal jejunum
D. 3rd part of duodenum
E. Appendix
D. 3rd part of duodenum
Intraperitoneal organs are housed within the
mesentary
The mesentary is a fusion of the parietal and layers of the peritoneum
visceral
A 41-year-old female presents to the ED with abdominal discomfort. CT indicates the presence of ascites. In which of the following locations would an ultrasound examination most likely confirm the presence of ascitic fluid with the patient in the supine position?
A. Hepatorenal recess (pouch of Morison)
What about pooling of fluid in the erect patient?
vesicouterine recess in a female
A patient presents with a peptic ulcer located in the posterior aspect of the duodenal bulb (cap). The ulcer has perforated the duodenal wall, resulting in profuse intra-abdominal bleeding. Which artery was most likely perforated by this ulcer?
A. Gastroduodenal
B. Left gastric
C. Right gastric
D. Right gastro-omental
E. Inferior pancreaticoduodenal
A. Gastroduodenal
The gastroduodenal artery and its branches supplies the most proximal aspect of the duodenum, just distal to the pyloric sphincter of the stomach. The right and left gastric aa. supply the lesser curvature.The right gastro-omental artery supplies the right aspect of the greater curvature. The inferior pancreaticoduodenal a. is a branch of the superior mesenteric artery, supplying the lower 1/2 of the duodenum (midgut).
Review the diagram of parts of stomach
Where do peptic ulcers commonly occur?
• Pyloris or proximal duodenum
Damage that can occur from a peptic ulcer includes:
- Erodes protective
- Vulnerable to gastric acids and enzymes
- Can erode through wall- risk of lethal
mucosa
digestive
hemorrhage
If gastric ulcer to posterior wall of stomach, were might fluids pool?
In the lesser sac behind the stomach
(review the other open spaces and sacs)
Review the branches of the celiac trunk
What are the 3 direct branches of the celiac trunk?
splenic artery
left gastric artery
common hepatic artery
What are the 3 branches of the splenic artery?
What branches off of the left gastric artery?
esophageal branches
The common hepatic artery has what 3 main branches?
hepatic artery proper
gastroduodenal artery
right gastric artery
The hepatic artery proper branches off to:
right hepatic-> cystic a.
left hepatic artery
the gastroduodenal artery (branch of the common hepatic a.) branches off to which 3 arteries?
What are the 5 branches of the superior mesenteric artery (SMA)?
- Inferior pancreaticoduodenal a. (anterior & posterior br.)
- Middle colic artery (right & left br.)
- Jejunal & Ileal arteries
- Right colic artery (ascending & descending br.)
- Ileocolic artery (superior & inferior br.)
What does the Inferior pancreaticoduodenal a. (anterior & posterior br.) supply?
- Distal duodenum
- Head (uncinate) of pancreas
What does the SMA branch middle colic artery supply?
transverse colon
What do the SMA branches of the jejunal and ileal arteries supply?
jejunum and ileum
What does the SMA branch right colic artery supply?
ascending colon
What does the SMA branch ileocolic artery (superior & inferior br.) supply?
Distal ileum, cecum, appendix, inferior ascending colon
What are the 3 direct branches of the inferior mesenteric artery (IMA)?
1. Left colic artery (ascending & descending br.)
• Distal transverse colon •
Superior descending colon
2. Sigmoid arteries
- Inferior descending colon
- Sigmoid colon
3. Superior rectal artery
• Superior rectum
What does the IMA branch Left colic artery (ascending & descending br.) supply?
- Distal transverse colon
- Superior descending colon
What do the direct IMA branch sigmoid arteries supply?
- Inferior descending colon
- Sigmoid colon
What does the direct IMA branch superior rectal artery supply?
superior rectum
There are 3 main arterial anastomoses to protect blood flow to the intestines, what are they and what branches do they anastomose?
- Pancreaticoduodenal aa (celiac trunk & SMA)
- Marginal artery (SMA & IMA), (Arc of Riolan- middle colic & left colic aa.)
- Rectal arteries (IMA & Internal iliac)
The marginal artery is the union between which 2 arteries?
the middle colic and left colic arteries and it supplies the left flexure
A 70-year-old male presents to the ED with severe diarrhea and ischemia to the descending colon. An arteriogram reveals a 90% blockage at the origin of the inferior mesenteric artery. Which of the following arteries would most likely provide collateral supply to the ischemic segment?
A. iliocoloic
B. middle colic
C. sigmoid
D. right colic
E. superior rectal artery
B. middle colic
B. Middle colic artery provides collateral circulation to the descending colon when IMA is obstructed. The superior rectal and sigmoid arteries are branches of the IMA. The Iliocolic supplies the inferior aspect of the ascending colon, cecum and appendix. The right colic supplies the ascending colon
Any time that someone has jaundice think:
Obstruction to the bile flow
A 44-year-old female presents to her primary care physician with nausea and RUQ pain for the last 2 days. Physical examination reveals scleral icterus (jaundice of the conjunctiva) and tenderness of the RUQ. She has a history of cholelithiasis, which is now obstructing a hepatobiliary duct. Which of the following structures has most likely been obstructed by the gallstone in this patient?
A. Right hepatic duct
B. Cystic duct
C. Left hepatic duct
D. Pancreatic duct
E. Bile duct
Bile duct
E. Bile duct. Jaundice results from reversal of bile flow into the bloodstream. The bile duct, if obstructed, allows no collateral pathway for drainage of bile from the liver or gallbladder. Obstruction of the cystic duct would block the cystic duct and possibly lead to cholecystitis, but would still permit bile flow from the liver. Obstruction of the right or left hepatic duct would similarly allow for bile drainage from the liver. The pancreatic duct is not involved in the bile pathway.
Explain where the following ducts are located and what they connect:
Right hepatic duct
Left hepatic duct
Common hepatic duct
Cystic duct
Common bile duct
pancreatic duct
What are gallstones (cholelithiasis)?
What is the more proper term for gallstones?
cholelithiasis
Asymptomatic or colic (when stone temporarily enters cystic duct)-intense, spasmodic pain in RUQ especially after a
biliary
meal
What is inflammation of the gallbladder and cystic duct due to obstruction and results in Pain in RUQ, epigastric region, shoulder?
Cholecystitis (gall bladder and cystic duct inflammation)
What can happen if there is chronic or recurrent cholecystitis?
adhesions to adjacent structures may develop (duodenum and transverse colon)
What can be created if gallbladder inflamed, may develop adhesions with adjacent viscera and May ulcerate tissue between gallbladder & GI tract?
Cholecysto-enteric fistula
What is gallstone ileus?
Inflammation of gallbladder leads to adhesions to adjacent duodenum creating a fistula where gallstones from gallbladder can travel to and clog the ileum ath the ileiocecal orifice (valve)
Chronic cholelithiasis can lead to scarring & calcification of wall which is called?
Porecelain gallbladder
(needs surgery or cholecystectomy)
Stone in bile duct leads to outflow obstruction of liver and gallbladder,
what is this condition?
choledocholithiasis
Choledocho- (bile duct) + lithiasis (stone) = choledocholithiasis
Outflow obstruction of liver due to stone in bile duct (or pancreatic cancer) can lead to inflammation of liver, ducts, and gallbladder.?
This can lead to jaundice because flow from gallbladder and liver is obstructed
Cholangitis
Cholang- (bile duct) + itis (inflammation) = cholangitis
What 3 structures make the Cystohepatic triangle (of Calot)?
Common hepatic duct, cystic duct, liver (cystic artery)
Where does the cystic artery most often arise from?
However, Variations in cystic artery origin & course of important consideration & common source of error
hepatic artery
A female is admitted to the ED with acute abdominal pain, nausea, and vomiting. Physical examination reveals tenderness in the right upper quadrant. Ultrasound confirms the presence of a large gallstone in the cystic duct. Visceral pain afferents from the cystic duct are carried in which of the following?
A. Greater splanchnic nerves
B. Intercostal nerves
C. Lesser splanchnic nerves
D. Phrenic nerves
E. Vagus nerves
A. Greater splanchnic nerves
A. The cystic duct and gallbladder are within in the foregut, which is innervated by the greater splanchnic (sympathetic) and vagus (parasympathetic) nn. Visceral afferent fibers travel with sympathetic pathways in this region.The afferent cell bodies associated with these receptors are location within the T5-T9 dorsal root ganglia. Visceral pain from the biliary system is primarily felt in the RUQ and epigastric region and referred along the T5-T9 dermatome.
Somatic pain from the liver & gallbladder is generally perceived in the right shoulder region. Why?
Somatic pain arising from irritation of the parietal peritoneum, the diaphragm. Phrenic nerve (C3-C5).
What part of the spinal cord receives all sensory input?
dorsal horn
What is Pain perceived at peripheral location other than site of painful stimulus?
referred pain
Describe the process of referred pain as concerning visceral and somatic efferents?
Convergence of visceral & somatic afferents results in “cross-talk” and confuses relationship of pain’s origin and its perception- brain misinterprets source
Where does referred pain “cross-talk” between viscera & somatic afferents occur?
dorsal horn of spinal cord
Explain the process of referred pain in the progression of cholecystisis?
- inflamed gallbladder sends afferent sensory info through greater splanchnic nerve to dorsal root ganglia where “cross-talk” occurs with the somatic afferents of dermatomes T5-T9
- Pain is then felt in the RUQ area of T5-T9
- Inflammation progresses to parietal peritoneum and diaphragm which is innervated by the phrenic nerve visceral afferents
- “Cross-talk” occurs at the level of the C3,C4, C5 and referred pain is then felt in the C3-C5 dermatomes of right shoulder area.
A 29-year-old male presents to the ED with a 3 month history of nausea and umbilical pain which has now progressed to a sharp, localized RLQ pain. Physical examination reveals rebound tenderness in the RLQ with abdominal guarding, and a positive Rovsing sign. A diagnosis of appendicitis is confirmed. Which of the following structures is most likely to transmit pain sensation from the inflammation?
A. Pelvic splanchnic nn.
B. Lumbar splanchnic nn.
C. Sacral splanchnic nn.
D. Greater splanchnic nn.
E. Lesser splanchnic nn.
E. Lesser splanchnic nn.
E. The appendix is derived from the embryonic midgut and receives innervation via the lesser splanchnic nn. (T10-T11). Visceral afferent fibers travel with sympathetic pathways in this region.The afferent cell bodies associated with these receptors are location within the T10-T11(T12) dorsal root ganglia. Visceral pain from the appendix is primarily felt in the umbilical region and RLQ and referred along the T10-T12 dermatome.
What is being described?
- Vermiform process (worm-like)
- Blind diverticulum (lymphoid)
located in the • Meso-appendix (mesentery proper)
and • Usually retrocecal position
appendix
What is Inflammation of appendix secondary to obstruction?
appendicitis
What are 2 major obstructions that can lead to appendicitis?
Causes: Fecaliths or Hyperplasia of lymphatic follicles
Describe the process of appendicitis from lumen occlusion to peritonitis or sepsis?
Occludes lumen -> inflammation -> ischemia -> Perforation/rupture -> Peritonitis or sepsis
Where is McBurney’s point and what is its significance?
- between umbilicus and the right anterior superior iliac spine
- typical area of appendix and where rebound tenderness can be felt
A 22 year old man suffers a penetrating knife wound to the abdomen that severs both the superior mesenteric artery and the vagus nerve. Which portion of the colon would most likely be impaired by this injury?
A. Ascending and descending colons
B. Transverse and sigmoid colons
C. Descending and sigmoid colons
D. Ascending and transverse colons
E. Transverse and descending colons
D. Ascending and transverse colons
D. Ascending and transverse colons receive blood from the SMA and parasympathetic nerve fibers from the vagus nerve. The descending and sigmoid colons receive blood from the IMA and parasympathetic nerve fibers from the pelvic splanchnic nerves
Where are the sympathetic autonomic (efferents) cell bodies for the foregut located and what is the nerve called and where does it synapse before it goes to the organs of the foregut?
T5-T9
Greater Splanchnic nerve
celiac ganglia
What is the parasympathetic innervation for the foregut and midgut and what is it’s path?
vagus nerve (CN X) with long presynaptics that synapse in the walls of the viscera
What is the path of sympathetic efferent innervation of the midgut and from which cell bodies does it originate?
originates from T10-T12
follows Lesser Splanchnic (T10,T11) and Least Splanchnic (T12) nerves
synapses in Superior Mesenteric Ganglion and travels to organs of midgut
Explain the sympathetic efferent path of the innervation of the Hindgut to superior rectum starting at the cell bodies?
originates at L1, L2 cell bodies
continues as the pre-synapric Lumbar Splanchnic Nerve
synapses at the Inferior Mesenteric Ganglia
Continues as post synaptics to the organs of Hindgut to the superior rectum
What is the parasympathetic efferent path of the hindgut starting at the cell bodies?
originates at S2-S4 cell bodes
follows Pelvic splanchnic nerve (only parasympathetic splanchnic nerve in the body)
synpases near or in the walls of the viscera
Explain the path of the sympathetics for the Hindgut- middle and inferior rectum?
cell bodies originate L1, L2 and presynaptics follow sympathetic chain
synapse in Lumbar Splanchnic n. (middle rectum)
and Sacral Splanchnic n. (inferior rectum)
postsynaptics follow to the middle and inferior rectum in hindgut
Other than the parasympathetics and sympathetics, what is the third and independent part of the ANS?
Enteric Nervous System
What is being described:
Network of interconnected ganglia within the gut wall (cell bodies of parasympathetic post-synaptic fibers, intrinsic neurons)
- Myenteric (or Auerbach’s) plexus & Submucosal (Meissner’s) plexus
- Networks form basis for reflex pathways
- 3rd & independent part of ANS (“2nd brain)
Functions without external innervation but influenced by autonomic input
Enteric Nervous System
What disease is being described?
Lack of autonomic ganglia due to failure of the neural crest cells to migrate distal to dilated segment causing megacolon
Hirschsprung’s disease (Megacolon)
