Two connected circuits
The right side of the heart pumps blood toward the lungs. The left side pumps blood to the body. Blood returns to the heart after each circuit.
Circulatory system
Follow blood through the heart, lungs and body.
Class notes
Open PDF →Three kinds of vessels
Arteries carry blood away from the heart; veins carry it toward the heart. Capillaries have thin walls that support exchange with surrounding tissues.
Blood as transport
Blood carries oxygen, nutrients and wastes. Red blood cells carry much of the oxygen; plasma carries dissolved materials. White blood cells and platelets have other important roles.
Follow blood through the heart
Rotate the heart, select its chambers and follow the two circuits.
Investigate
Keep stroke volume constant. Compare the cardiac output at rest with a faster heart rate.
Make the connection
Trace blood from the right ventricle to the lungs and back to the left side of the heart. Red and blue indicate oxygen level; blood is never blue.
If the model cannot load on your device, use the illustrated class notes above and the pathway below to trace the same structures.
Explore this idea further
Watch: Circulatory and respiratory systems · Crash Course
Follow blood through the heart, lungs and body.
Open on YouTube →Are all arteries oxygen-rich?
Reveal the reasoning
No. Arteries are defined by direction away from the heart. The pulmonary artery carries oxygen-poor blood toward the lungs.
Try it yourself.
The pulmonary artery carries blood from the heart to the lungs. Is it an artery even though it carries oxygen-poor blood?
Check your thinking
Yes. Arteries are defined by the direction blood travels: away from the heart.
Take it further.
Explain why capillaries connect the circulatory system with other body systems.
See a possible explanation
Their thin walls allow materials to move between blood and surrounding tissues, connecting circulation with cells throughout the body.