Lesson 1 of 7 / Transport in humans
Blood vessels and circulation routes
Which vessel takes blood to each organ, and which brings it back?
I can trace the main vessels linking the heart, lungs, liver and kidneys.
I can identify main vessels linking the heart, lungs, liver and kidneys.Syllabus
Syllabus K224 / K225, Topic 5(a). Identify main vessels linking the heart, lungs, liver and kidneys.
About 5 min
Make a guess. You are not marked.
Arteries are often drawn in red for oxygen-rich blood. Is there an artery that carries oxygen-poor blood?
Show the answer
Yes, the pulmonary artery to the lungs.
An artery is any vessel carrying blood away from the heart. The pulmonary artery carries oxygen-poor blood to the lungs.
The key idea
Arteries carry blood away from the heart; veins return it. The vessel name identifies the organ or route.
A circulation map shows connections, not the positions or sizes of organs. Follow each arrow before deciding what the blood contains.
- Pulmonary artery: right ventricle to lungs
- Pulmonary veins: lungs to left atrium
Explanation
Humans have a double circulation. In one full trip round the body, blood passes through the heart twice. The right side of the heart pumps blood to the lungs. The left side pumps blood to the rest of the body.
Blood leaves the right ventricle in the pulmonary artery. It picks up oxygen in the capillaries of the lungs and comes back in the pulmonary veins to the left atrium. The left ventricle pumps it into the aorta. Branches of the aorta take blood to the organs, and veins bring it back to the venae cavae and the right atrium.
The liver has two blood supplies coming in. The hepatic artery brings oxygen-rich blood from the aorta. The hepatic portal vein brings blood full of absorbed food from the small intestine. Blood leaves the liver in the hepatic vein.
A renal artery takes blood from the aorta to each kidney. A renal vein takes blood from the kidney back to the vena cava. The ureter carries urine, not blood.
"Oxygenated" means rich in oxygen, and "deoxygenated" means low in oxygen. Deoxygenated blood still has some oxygen. Not every artery carries oxygenated blood: the pulmonary artery carries deoxygenated blood to the lungs.
Step by step
- 1
Pick a starting point
For example, start at the left ventricle. Do not just list vessel names.
- 2
Follow the direction
Use an artery on the way out from the heart and a vein on the way back.
- 3
Check the liver route
Blood from the small intestine goes to the liver in the hepatic portal vein before it goes back to the heart.
Worked example
From intestine to heart
Trace blood carrying recently absorbed glucose from the small intestine to the right atrium.
One way to explain it
Small-intestinal capillaries -> hepatic portal vein -> liver capillaries -> hepatic vein -> vena cava -> right atrium.
Why this answer works
- The liver receives absorbed nutrients before they reach the general circulation.
- Portal identifies the connection between two capillary beds.
- The hepatic vein, not the portal vein, leaves the liver for the vena cava.
Watch out for this
A student says: "The hepatic portal vein carries blood out of the liver." What is wrong with this?
Show the answer
It brings blood from the small intestine into the liver. The hepatic vein carries blood out.
Check your understanding
Which route correctly takes blood from the aorta through a kidney and back towards the heart?
Show the answer
Aorta -> renal artery -> kidney -> renal vein -> vena cava
Arterial blood reaches the kidney, and venous blood returns towards the heart.
Quick recall
Which vessel takes blood to each organ, and which brings it back?