Step 1: what comes next?
Preganglionic neuron leaves thoracolumbar cord
The cell body lies in the intermediolateral column.
GI
Gastrointestinal Blood Supply and Innervation
Foregut, midgut, and hindgut each carry a matching artery, parasympathetic source, and prevertebral plexus.
- Match gut regions to arterial and parasympathetic supply
- Identify celiac-trunk branches and gastric anastomoses
- Trace sympathetic fibers through prevertebral ganglia
Anatomic relationships
Use the landmarks before naming the lesion
The figure shows the location and nearby structures that distinguish the diagnosis.
Quick check
A lesion affects the distal one third of the transverse colon and interrupts its parasympathetic supply.
Which nerves provide the interrupted fibers?
Reason it through
- Which embryologic territory begins here?The hindgut starts at the distal one third of the transverse colon.
- What parasympathetic source serves that territory?Pelvic splanchnic nerves from S2 through S4 supply the hindgut.
Follow the stomach's arterial arcades
Each gastric curvature carries a paired arterial route with an anastomosis.
Left and right gastric arteries run together along the lesser curvature within the lesser omentum.
Left and right gastroepiploic arteries communicate along the greater curvature through the greater omentum.
Short gastric arteries leave the splenic artery for the fundus through the gastrosplenic ligament, where collateral options are less redundant.
Open each curvature and vessel pair.
Left gastric from celiac meets right gastric, usually from proper or common hepatic circulation.
Left gastroepiploic from splenic meets right gastroepiploic from gastroduodenal.
Short gastric arteries travel from splenic artery through gastrosplenic ligament.
Superior pancreaticoduodenal branches arise from gastroduodenal circulation and meet SMA branches.
Region, artery, and parasympathetic nerve
Artery, parasympathetic nerve, and embryologic region are three columns of one map.
Foregut derivatives receive celiac arterial supply and parasympathetic input from the vagus nerve.
Midgut derivatives pair the superior mesenteric artery with vagal fibers through the proximal two thirds of the transverse colon.
Hindgut derivatives pair the inferior mesenteric artery with pelvic splanchnic fibers from S2 through S4.
Switch among the three regions.
Celiac trunk; vagus; lower esophagus through proximal duodenum plus liver, biliary tree, and pancreas.
SMA; vagus; distal duodenum through proximal two thirds of transverse colon.
IMA; pelvic splanchnics S2-S4; distal one third of transverse colon through upper anal canal.
Celiac-vagus, SMA-vagus, IMA-pelvic.
Sympathetic fibers take a different route
Sympathetic fibers cross the chain before synapsing near the abdominal aorta.
Thoracic and lumbar splanchnic nerves carry preganglionic sympathetic fibers toward prevertebral ganglia instead of synapsing in the paravertebral chain.
Celiac, superior mesenteric, and inferior mesenteric ganglia and plexuses send postganglionic fibers along arterial branches to the bowel.
Sympathetic activation generally reduces motility and secretion, contracts sphincters, constricts vessels, and carries visceral pain afferents toward thoracolumbar levels.
Reveal the sympathetic path.
Step 2: what comes next?
Fiber enters sympathetic chain
It passes through without synapsing for abdominal visceral supply.
Step 3: what comes next?
Splanchnic nerve crosses toward aorta
Greater, lesser, least thoracic, or lumbar splanchnic pathways carry the fiber.
Step 4: what comes next?
Synapse occurs in prevertebral ganglion
Celiac or mesenteric ganglia organize region-specific output.
Step 5: what comes next?
Postganglionic fibers follow arteries
Periarterial plexuses reach bowel wall and sphincters.
The celiac trunk has three first branches
Start with the celiac triad before following its smaller branches.
The celiac trunk classically divides into left gastric, splenic, and common hepatic arteries for foregut structures.
Common hepatic circulation gives rise to gastroduodenal and proper hepatic pathways, while the splenic artery supplies pancreatic, short gastric, and left gastroepiploic branches.
The left gastric artery ascends to the lower esophagus and follows the lesser curvature to meet the right gastric artery.
Which artery is not a primary celiac-trunk branch?
Choose the first item.
Left gastric, splenic, common hepatic: the celiac three.
Match artery origins to vertebral levels
Origin levels provide a fast check on an unlabeled axial image.
Celiac trunk arises near T12, superior mesenteric artery near L1, and inferior mesenteric artery near L3.
That descending order mirrors foregut, midgut, and hindgut territories along the bowel.
Classify each root as relatively higher or lower.
T12, L1, L3: celiac, SMA, IMA.
Arterial borders create collateral routes
Collateral pathways matter most where arterial territories meet.
Superior and inferior pancreaticoduodenal arcades connect celiac and SMA supply around the duodenum and pancreatic head.
The marginal artery links colic branches along the colon and can connect SMA with IMA territories when the arcade is complete.
Rectal circulation joins superior rectal portal drainage with middle and inferior rectal systemic drainage, forming a portosystemic site rather than a simple arterial collateral.
Open each collateral route.
Superior and inferior pancreaticoduodenal arcades meet around pancreatic head and duodenum.
Middle colic and left colic branches communicate through the marginal artery near splenic flexure.
Superior rectal circulation approaches middle rectal branches in the pelvis.
Collateral anatomy varies, so border zones remain vulnerable during low flow.
Stage 1 of 3: Overview
Overview
Gastrointestinal Blood Supply and Innervation
Sympathetic fibers cross the chain before synapsing near the abdominal aorta.
Localization check
Which landmark matters most?
Choose the location that rules the other answer choices in or out.
Which nerves provide the interrupted fibers?
- Key finding. distal one third of the transverse colon
- Answer. Pelvic splanchnic nerves from S2 through S4
- Why. This segment is hindgut and receives parasympathetic fibers from pelvic splanchnic nerves.
- Board rule. At the distal transverse-colon third, parasympathetic supply changes from vagus to pelvic splanchnics.
Match vessel, territory, and nerve
The set links a bleeding ulcer, operative denervation, an arterial level, a gastric anastomosis, and a sympathetic pathway.
Cross out wrong locations and highlight the decisive landmark. Each case connects anatomy to its clinical consequence.
A posterior ulcer in the first part of the duodenum erodes an adjacent artery and produces brisk upper gastrointestinal bleeding.
Which artery is most likely injured?
Reason it through
- Which surface of the proximal duodenum contains the ulcer?The lesion is posterior, where a major artery passes behind D1.
- What vessel occupies that relationship?The artery crosses behind the proximal duodenum, where a posterior ulcer can erode it.
- Why is the left gastric artery less likely here?Left gastric circulation follows the lesser curvature and lower esophagus rather than the posterior duodenal wall.
posterior ulcer in the first part of the duodenumWhat vessel occupies that relationship?
- Which surface of the proximal duodenum contains the ulcer?The lesion is posterior, where a major artery passes behind D1.
- What vessel occupies that relationship?The artery crosses behind the proximal duodenum, where a posterior ulcer can erode it.
- Why is the left gastric artery less likely here?Left gastric circulation follows the lesser curvature and lower esophagus rather than the posterior duodenal wall.
During right-colon surgery, vagal fibers traveling to the ascending colon are interrupted.
Which embryologic gut territory lost parasympathetic input?
Reason it through
- Which colon segment was denervated?The ascending colon is the injured target.
- What developmental territory includes that segment?Ascending colon belongs to the midgut and normally receives vagal parasympathetic input.
- Which colonic region would instead depend on pelvic splanchnics?Hindgut beginning at the distal transverse-colon third receives S2 through S4 fibers.
vagal fibers traveling to the ascending colonWhat developmental territory includes that segment?
- Which colon segment was denervated?The ascending colon is the injured target.
- What developmental territory includes that segment?Ascending colon belongs to the midgut and normally receives vagal parasympathetic input.
- Which colonic region would instead depend on pelvic splanchnics?Hindgut beginning at the distal transverse-colon third receives S2 through S4 fibers.
Angiography shows occlusion of an unpaired anterior aortic branch arising near L3. The threatened bowel segment is supplied from the hindgut territory.
Which structure is most directly threatened?
Reason it through
- Which major artery originates near L3?The inferior mesenteric artery arises at this level.
- What embryologic territory does that branch supply?IMA circulation serves hindgut structures, including descending colon.
- Why would proximal small bowel not be the primary target?Small bowel lies in SMA midgut territory rather than the L3 IMA field.
unpaired anterior aortic branch arising near L3What embryologic territory does that branch supply?
- Which major artery originates near L3?The inferior mesenteric artery arises at this level.
- What embryologic territory does that branch supply?IMA circulation serves hindgut structures, including descending colon.
- Why would proximal small bowel not be the primary target?Small bowel lies in SMA midgut territory rather than the L3 IMA field.
During gastric surgery, the dissection follows an artery from the celiac trunk until it meets the right gastric artery along one border of the stomach.
Which gastric border contains this anastomosis?
Reason it through
- Which celiac branch is being followed?The left gastric artery is the celiac branch that meets the right gastric artery.
- Where do those paired vessels run?They anastomose along the lesser curvature within the lesser omentum.
- What arteries would mark the opposite curvature?Left and right gastroepiploic arteries travel along the greater curvature.
meets the right gastric arteryWhere do those paired vessels run?
- Which celiac branch is being followed?The left gastric artery is the celiac branch that meets the right gastric artery.
- Where do those paired vessels run?They anastomose along the lesser curvature within the lesser omentum.
- What arteries would mark the opposite curvature?Left and right gastroepiploic arteries travel along the greater curvature.
A preganglionic sympathetic fiber enters the paravertebral chain but does not synapse there. It continues toward a ganglion beside the abdominal aorta.
Which pathway carries the fiber next?
Reason it through
- What distinguishes this fiber inside the chain?It passes through the sympathetic chain without synapsing.
- How does it reach the prevertebral ganglia?A thoracic or lumbar splanchnic nerve carries it toward the aorta.
- Where will its postganglionic fibers travel afterward?They distribute from prevertebral plexuses along arterial branches to the bowel.
does not synapse thereHow does it reach the prevertebral ganglia?
- What distinguishes this fiber inside the chain?It passes through the sympathetic chain without synapsing.
- How does it reach the prevertebral ganglia?A thoracic or lumbar splanchnic nerve carries it toward the aorta.
- Where will its postganglionic fibers travel afterward?They distribute from prevertebral plexuses along arterial branches to the bowel.
Rapid review
Three questions to check
Which nerves provide the interrupted fibers?
Pelvic splanchnic nerves from S2 through S4. This segment is hindgut and receives parasympathetic fibers from pelvic splanchnic nerves.
Which surface of the proximal duodenum contains the ulcer?
The lesion is posterior, where a major artery passes behind D1.
What vessel occupies that relationship?
The artery crosses behind the proximal duodenum, where a posterior ulcer can erode it.
Medically reviewed
Fatima Ali, DO
PGY-1 Resident Physician in Psychiatry
University Hospitals, Columbia
DO from Kansas City University
Resident physician and founding medical reviewer at Bone Wizardry, focused on clinical accuracy, clear diagnostic reasoning, and practical board-oriented teaching across the curriculum.
Languages: English, Urdu
Primary reviewerFull physician profile
Medically reviewed
Sources
- Embryology, Gastrointestinal2026
- Anatomy, Abdomen and Pelvis: Abdominal Aorta2026
- Anatomy, Abdomen and Pelvis: Superior Mesenteric Artery2026
- Anatomy, Abdomen and Pelvis, Small Intestine2026
- Anatomy, Abdomen and Pelvis: Anal Canal2026
Bone Wizardry is a study resource for medical students. It is not medical advice.