GI Vasculature, Lymphatics, and Innervation: Regional Supply Patterns from Foregut to Hindgut

Using Vessels as an Anatomical Map: Foregut, Midgut, Hindgut

A practical way to organize GI regional anatomy is to follow the three major unpaired arterial trunks of the abdominal aorta and treat their territories as “regions on a map.” Each region tends to share a dominant arterial source, a characteristic venous route (often into the portal system), and predictable lymph node “stations” that sit along the same named vessels.

Boundary cue: The transition from foregut to midgut is classically placed around the major duodenal papilla region; the transition from midgut to hindgut is around the distal third of the transverse colon (near the splenic flexure). These boundaries help you predict which named vessels, nodes, and nerve plexuses you should look for.

Arterial Supply Patterns: Celiac Trunk, SMA, IMA

Celiac trunk (foregut trunk)

The celiac trunk quickly divides into three major branches. Use them as “routes” to specific foregut organs and as landmarks for accompanying veins, lymphatics, and autonomic plexuses.

• Left gastric artery: runs along the lesser curvature region; supplies abdominal esophagus and lesser curvature territory.
• Splenic artery: courses toward the spleen; gives pancreatic branches and short gastric/left gastro-omental branches to stomach.
• Common hepatic artery: supplies liver via hepatic artery proper and contributes to stomach/duodenum via branches (e.g., gastroduodenal pathway).

Practical mapping tip: If you can name the artery running along a curvature (lesser vs greater) or heading to the porta hepatis, you can usually infer the lymph node group and the nerve plexus traveling with it.

Superior mesenteric artery (midgut trunk)

The SMA is the “mesenteric fan” artery: it travels into the mesentery and distributes branches that arc and then send straight vessels to bowel. Think in two layers: (1) named branches leaving the SMA, then (2) arcades and vasa recta supplying the intestinal wall.

Continue in our app.

• Listen to the audio with the screen off.
• Earn a certificate upon completion.
• Over 5000 courses for you to explore!

Or continue reading below...

Download the app

• Inferior pancreaticoduodenal artery: distal duodenum/pancreatic head region (midgut side of the duodenum).
• Jejunal and ileal arteries: form arterial arcades in the mesentery; vasa recta reach the bowel wall.
• Ileocolic artery: terminal ileum, cecum, appendix region.
• Right colic artery: ascending colon region (variable).
• Middle colic artery: transverse colon (proximal portion).

Step-by-step: tracing SMA blood to small intestine on imaging or in dissection

1. Find the SMA at its origin from the aorta and follow it into the mesentery.
2. Identify a jejunal/ileal branch entering the mesenteric “fan.”
3. Follow it into arterial arcades (loops).
4. From an arcade, follow a vasa recta (straight vessel) to the bowel wall.
5. Use the same path in reverse to predict where lymphatics and nerves will run (they accompany arteries back toward the root of the mesentery).

Inferior mesenteric artery (hindgut trunk)

The IMA supplies the left-sided colon and upper rectum through a smaller set of named branches. These branches also provide a clean “node map” because lymph nodes are often named for the same vessels.

• Left colic artery: descending colon and distal transverse region near the splenic flexure.
• Sigmoid arteries: sigmoid colon.
• Superior rectal artery: upper rectum (continuation of IMA).

Clinical-anatomy orientation: The splenic flexure is a common “watershed” area where territories meet; it is a useful landmark when you are deciding whether a segment is more SMA- or IMA-dominant.

Venous Drainage: Following Gut Blood to the Liver (Portal System Emphasis)

Most GI venous blood (from abdominal GI organs) drains into the portal venous system, which delivers nutrient-rich blood to the liver before it returns to the systemic circulation. The portal vein is formed by major tributaries that mirror the arterial map: veins often “shadow” arteries and share names.

Core portal pathway

• Superior mesenteric vein (SMV): drains midgut structures; runs with the SMA in the mesentery.
• Splenic vein: drains spleen and receives pancreatic veins; commonly receives the inferior mesenteric vein.
• Portal vein: typically formed by the union of the SMV and splenic vein; carries blood to the liver at the porta hepatis.

Step-by-step: “How does blood from the ileum reach the liver?”

1. Venules in the ileal wall converge into veins that travel with the vasa recta.
2. These drain into venous channels alongside the arterial arcades within the mesentery.
3. They converge into larger ileal veins that empty into the SMV.
4. The SMV joins the splenic vein to form the portal vein.
5. The portal vein enters the liver at the porta hepatis and distributes into intrahepatic portal branches.

Foregut venous patterns (named veins that mirror arteries)

• Left and right gastric veins drain the lesser curvature region into the portal vein (directly or via short pathways).
• Short gastric veins and left gastro-omental vein typically drain toward the splenic vein.
• Right gastro-omental vein typically drains toward the SMV.

Midgut and hindgut venous patterns

• SMV tributaries drain jejunum/ileum and much of the right and transverse colon (via ileocolic, right colic, middle colic veins).
• Inferior mesenteric vein (IMV) drains hindgut (left colic, sigmoid, superior rectal veins) and most often empties into the splenic vein (variable anatomy exists).

Key organizing idea: If an organ is supplied by SMA, expect venous return to SMV; if supplied by IMA, expect venous return to IMV (then to splenic vein); foregut venous return is split among portal, splenic, and SMV tributaries depending on the specific stomach/pancreas/spleen-adjacent territory.

Lymphatic Drainage: Nodes Named by Proximity and Vessels as “Highways”

GI lymphatics generally follow arteries backward: from the organ wall into small local nodes, then along named vessels to larger collecting nodes near the aorta. A practical naming rule is that many node groups are named for the organ surface they sit near (e.g., gastric) or for the vessel/mesentery they accompany (e.g., mesenteric, colic).

Concept: three “tiers” you can look for

• Peri-organ (epicolic/perigastric) nodes: closest to the organ (e.g., along stomach curvatures; along colon wall).
• Intermediate nodes along named vessels: along gastric, mesenteric, colic vessels.
• Central (preaortic) nodes: clustered around the origins of celiac, SMA, and IMA (celiac, superior mesenteric, inferior mesenteric node groups).

Foregut lymph routes (gastric and celiac focus)

Stomach and proximal duodenum lymph commonly drains first to gastric nodes positioned along the lesser and greater curvature territories, then to celiac nodes near the celiac trunk origin.

• Gastric nodes: along left/right gastric vessels and along gastro-omental/short gastric pathways.
• Hepatic nodes: along hepatic artery/porta hepatis region (important for liver/gallbladder drainage pathways).
• Pancreaticosplenic nodes: along splenic artery region (pancreas tail/spleen-adjacent drainage).
• Celiac nodes: central collection for foregut-associated drainage.

Midgut lymph routes (mesenteric focus)

Small intestine lymphatics travel within the mesentery: from intestinal wall → mesenteric nodes → superior mesenteric nodes near the SMA origin.

• Mesenteric nodes: distributed along jejunal/ileal vessels within the mesentery.
• Ileocolic/right colic/middle colic nodes: intermediate “colic” stations for right colon and proximal transverse colon.
• Superior mesenteric nodes: central collection near SMA.

Hindgut lymph routes (colic focus)

Left colon and upper rectum lymph commonly passes through colic nodes (left colic, sigmoid) and then to inferior mesenteric nodes near the IMA origin.

• Left colic nodes: along left colic vessels.
• Sigmoid nodes: along sigmoid vessels.
• Inferior mesenteric nodes: central collection near IMA.

Mesenteries as conduits: Mesentery and mesocolon act like “bundles” that carry arteries, veins, lymphatics, and nerves together. When you locate a named vessel in a mesentery, you have also located the likely lymphatic route and autonomic plexus distribution path.

Autonomic Innervation Overview: Where Nerves Travel (Not Physiology)

Autonomic fibers reach the gut by traveling along arteries and forming plexuses around major vessels. A useful approach is to learn the source (parasympathetic vs sympathetic) and the distribution route (which plexus and which arteries they follow).

Parasympathetic pathways

• Vagus nerves: distribute to foregut and midgut by entering the abdomen and contributing fibers to plexuses around the celiac trunk and SMA; fibers then “ride along” branches to target organs.
• Pelvic splanchnic nerves (S2–S4): distribute to hindgut (especially distal colon/rectum) via the inferior hypogastric plexus and then along vessels to the gut.

Sympathetic pathways

Sympathetic fibers reach abdominal organs via thoracic and lumbar splanchnic nerves, synapse in prevertebral ganglia, then distribute along periarterial plexuses.

• Greater thoracic splanchnic → synapse in/near celiac ganglia → fibers follow celiac trunk branches (foregut distribution).
• Lesser/least thoracic splanchnic → contribute to plexuses associated with celiac/SMA regions (often described with aorticorenal/superior mesenteric ganglia contributions).
• Lumbar splanchnic → synapse in/near inferior mesenteric ganglion → fibers follow IMA branches (hindgut distribution).

Plexuses you should be able to “place” anatomically

• Celiac plexus: around the celiac trunk origin; distributes along left gastric, splenic, and common hepatic arteries.
• Superior mesenteric plexus: around SMA; distributes along jejunal/ileal and colic branches.
• Inferior mesenteric plexus: around IMA; distributes along left colic, sigmoid, and superior rectal arteries.
• Hypogastric plexuses (superior and inferior): key relay regions for pelvic distribution; connect hindgut pathways to pelvic organs and vessels.

Step-by-step: predicting nerve route to an organ

1. Identify the organ’s primary arterial trunk (celiac vs SMA vs IMA).
2. Locate the corresponding periarterial plexus (celiac, superior mesenteric, inferior mesenteric).
3. Trace the named arterial branch to the organ; assume autonomic fibers accompany it in the same connective tissue sheath.
4. For distal hindgut/pelvic targets, add the hypogastric plexus pathway as the “gateway” into the pelvis.

Consolidation Activity: Match Organ → Artery → Venous Outflow → Major Lymph Node Group

Instructions: For each organ/segment, write (1) primary arterial supply, (2) main venous route (portal tributary), and (3) major lymph node group. Use the word bank if helpful.

Word bank

• Arteries: Celiac trunk (left gastric / splenic / common hepatic), SMA (jejunal/ileal / ileocolic / middle colic), IMA (left colic / sigmoid / superior rectal)
• Veins: Portal vein, Splenic vein, SMV, IMV
• Lymph nodes: Gastric, Hepatic, Pancreaticosplenic, Mesenteric, Ileocolic/Right colic/Middle colic, Left colic, Sigmoid, Celiac, Superior mesenteric, Inferior mesenteric

Self-check approach: After filling the table, circle each row’s arterial trunk (celiac/SMA/IMA). Your venous and lymph answers should “cluster” the same way: celiac rows tend toward portal/splenic tributaries and celiac/gastric/hepatic/pancreaticosplenic nodes; SMA rows tend toward SMV and superior mesenteric/mesenteric/ileocolic-right-middle colic nodes; IMA rows tend toward IMV (often to splenic) and inferior mesenteric/left colic/sigmoid nodes.