🟢 Purpose of Systemic Circulation:
To send oxygenated blood to all body tissues and return deoxygenated blood to the heart.
❤️🔥 3. Coronary Circulation – Blood for the Heart Muscle
You might ask, “If the heart pumps blood, who supplies blood to the heart itself?”
Good question! The heart muscle (myocardium) needs its own blood supply, and that’s what coronary circulation does.
- Coronary arteries branch off from the aorta and supply oxygen-rich blood directly to the heart muscle.
- These arteries branch into smaller vessels: arterioles → capillaries.
- After giving oxygen to the heart cells, the capillaries collect into venules → coronary veins.
- These veins join to form the coronary sinus, a large vein that opens into the right atrium of the heart.
💡 Example: If you have ever heard of someone having a “heart attack,” it usually happens when a coronary artery gets blocked, and part of the heart muscle doesn’t get oxygen.
🍽️ 4. Hepatic Portal Circulation – Blood for Processing in the Liver
Now here comes a special system — not every vein in the body goes straight back to the heart.
The hepatic portal circulation is a shortcut where blood from the digestive system first goes to the liver before reaching the heart.
Why?
Because the blood from the stomach, intestines, and spleen carries digested food, toxins, and other substances. The liver acts like a filter and processing plant.
Steps:
- Veins from the digestive organs (like stomach, intestines, spleen) collect nutrient-rich blood.
- These veins join to form the hepatic portal vein.
- The hepatic portal vein takes this blood to the liver.
- The liver:
- Stores nutrients like glucose
- Removes harmful substances like drugs, alcohol, and bacteria
- Processes nutrients for later use
- The cleaned blood leaves the liver through hepatic veins, which finally join the inferior vena cava, and the blood returns to the heart.
💡 Example: After eating a meal, your liver decides how much glucose to store, how much fat to break down, and whether to remove toxins like alcohol from your bloodstream.
🚰 5. Renal Circulation – Blood Filtration in the Kidneys
Your kidneys act like a filtering plant for the blood. They remove extra water, salts, and wastes from the blood to form urine.
Steps:
- Renal arteries carry oxygenated, unfiltered blood to the kidneys.
- Inside the kidney:
- Arteries branch into afferent arterioles
- These lead to a tiny knot of capillaries called a glomerulus
- Blood is filtered here: wastes and water move out, useful things stay
- From the glomerulus, blood exits through the efferent arteriole.
- This blood then flows through:
- Peritubular capillaries (in the kidney cortex)
- Vasa recta (in the kidney medulla)
- These capillaries absorb water, nutrients, and salts back into the blood as needed.
- The cleaned blood flows into venules, then into the renal vein, and finally returns to the heart.
💡 Example: When you drink a lot of water, your kidneys filter more, and you urinate more. The renal circulation adjusts accordingly.
🔁 Quick Recap – Pathways and Their Roles
| Circulatory Pathway | Purpose |
| Pulmonary | Blood to lungs for gas exchange |
| Systemic | Blood to all body tissues |
| Coronary | Supplies blood to heart muscle |
| Hepatic Portal | Takes blood from digestive tract to liver for processing |
| Renal | Filters blood through kidneys to form urine |
🧠 Why Learn This?
Understanding these pathways helps you know:
- Why heart problems affect the whole body
- How your liver and kidneys clean and balance your blood
- How oxygen gets from your lungs to your toes