14/08/2026
Let’s talk about the spleen—a pretty underrated organ hanging out in your upper left belly. People rarely think about it unless something goes wrong, but honestly, it’s a key player connecting your blood, immune system, splenic vein, portal vein, and liver.
So, the main route to remember is:
Spleen → Splenic Vein → Portal Vein → Liver
That pathway’s part of the hepatic portal system—a sort of traffic highway that shuttles nutrients and blood from various abdominal organs straight to the liver for processing.
Ready for a deep dive? Here’s how it all fits together.
🩸 1. Where’s the Spleen?
You’ll find the spleen tucked under your left rib cage, just underneath the diaphragm. It’s close to your stomach, left kidney, pancreas, and the lower left ribs protect it pretty well. While everyone’s anatomy is a little different, those relationships—with the stomach, diaphragm, and kidney—are important for understanding how the abdomen works.
🫘 2. What Does it Look Like?
The spleen’s kind of oval-shaped or like a wedge. It’s got two distinct surfaces (diaphragmatic and visceral), front and back borders, superior and inferior poles, and a hilum. That hilum—think of it like the “gate”—is where blood vessels and other stuff come and go.
🔬 3. The Spleen’s Main Zones
If you peek under the microscope, the spleen breaks into two parts:
🔴 Red Pulp: This area filters blood. It pulls out old or wonky red blood cells and supports some immune functions.
⚪ White Pulp: Packed with lymphoid tissue, this part watches the blood for anything nasty—like foreign substances or pathogens.
With both regions working together, the spleen cleans up your blood and helps your body fight off threats.
🩸 4. Where Does its Blood Come From?
The splenic artery brings blood in. It’s a major branch off the celiac trunk, which comes from the abdominal aorta. So, the route is:
Abdominal Aorta → Celiac Trunk → Splenic Artery → Spleen
This artery snakes along the top edge of the pancreas and splits near the hilum to supply different parts of the spleen.
🔵 5. How Does Blood Leave the Spleen?
Blood exits via the splenic vein. This vein slips out through the hilum and heads toward the right side, running behind the pancreas. The splenic vein’s job is to carry blood away from the spleen and toward the liver’s portal system.
🩸 6. What’s the Portal Vein?
The portal vein heads toward the liver, shuttling blood from your digestive tract and spleen. It forms when the splenic vein joins up with the superior mesenteric vein—usually right behind the neck of the pancreas. So, it’s not a straight shot from the spleen; these two veins merge to create the portal vein.
🧠 7. The Spleen-to-Liver Route
Here’s the journey:
🩸 Spleen
⬇️
🔵 Splenic Vein
⬇️
🔵 Joins Superior Mesenteric Vein
⬇️
🩸 Portal Vein
⬇️
🫀 Liver
This route is a classic in abdominal anatomy.
🫀 8. Why Send Blood to the Liver?
The liver’s like your body’s processing center. Blood comes in carrying all kinds of stuff—nutrients, metabolic products, antigens, and even drugs. The liver stores, processes, detoxifies, and tweaks these substances before releasing them into the general circulation. The spleen’s blood joins this party even though it doesn’t digest food—it still contains plenty of useful (and sometimes dangerous) things that need the liver’s attention.
🩸 9. What’s the Hepatic Portal System?
This system is special. Instead of blood rushing straight back to the heart after visiting the abdominal organs, it passes through the liver first. The veins from the spleen, stomach, intestines, pancreas, and other digestive bits all feed into this system—letting the liver take a first look at everything you’ve absorbed or made.
🫀 10. Liver’s Two Blood Sources
The liver’s got a dual supply:
🔴 Hepatic Artery: Brings in oxygen-rich blood.
🔵 Portal Vein: Brings a flood of blood from abdominal organs.
Both sources pour into the liver’s microscopic channels—sinusoids—so liver cells can do their thing.
🧩 11. What Happens Inside the Liver?
Blood from both the artery and portal vein travels through those sinusoids. Hepatocytes—liver’s main workers—line these channels. They’re busy with metabolism, glucose regulation, drug processing, protein and lipid synthesis, handling waste, and making key plasma proteins. Basically, the liver’s your body’s factory and processing center.
🔬 12. The Splenic Vein’s Other Connections
The splenic vein doesn’t just drain the spleen. It collects blood from the pancreas, short gastric veins, and the left gastroepiploic vein, weaving together a network linking the spleen, stomach, pancreas, and portal system. Anatomy varies, but these connections all matter.
⚠️ 13. What’s Portal Hypertension?
If blood hits resistance in the liver or portal system, pressure spikes—this is portal hypertension. It’s often linked to chronic liver issues. When pressure gets too high, blood finds alternative routes (portosystemic collaterals), and that can trigger complications needing medical attention.
🩸 14. The Spleen’s Role in Portal Hypertension
Since the spleen drains straight into the portal system, rising pressure can back up—it ends up congested and sometimes enlarged (splenomegaly). An enlarged spleen affects blood cell counts since it can trap them. But keep in mind, splenomegaly has many causes, so don’t jump straight to liver disease without checking with a doctor.
🧠 15. Quick Memory Trick
Think:
“Spleen → Splenic → Portal → Liver”
🩸 Spleen
⬇️
🔵 Splenic vein
⬇️
🔵 Superior mesenteric vein joins
⬇️
🩸 Portal vein
⬇️
🫀 Liver
The portal vein is like a delivery truck—hauling blood from those organs to the liver before it circulates everywhere else.
🌟 The Big Picture
The spleen, splenic vein, portal vein, and liver form a beautifully coordinated vascular network. The spleen filters and supports immunity; the splenic vein drains it; the portal vein forms and carries blood to the liver; and the liver processes everything. Understanding this blood flow is just as vital as knowing where organs sit—because what’s happening inside matters just as much.
Keep this guide handy. Share it with anyone tackling human anatomy!
⚠️ Disclaimer
This guide is for educational purposes. For any health concerns, always check with a professional.