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📘 A pump with two loops

Look at your wrist: each pulse is a pressure wave from a four-chamber pump. That pump keeps two linked circuits moving, one through the lungs and one through the body.

4
lessons
~20 min
to learn
Adults
level
Start the course →

What you’ll learn

  1. A two-sided pumpIdentify the four chambers, the two circuits, and the direction of blood flow through the heart.The right heart sends oxygen-poor blood to the lungs; the left heart sends oxygen-rich blood to the body. Atria receive, ventricles eject, and a septum keeps the two streams separate. Valves make the route one-way.
  2. The beat is a cycleExplain how filling, contraction, relaxation, and pressure changes create one cardiac cycle.Diastole fills the chambers and systole ejects blood. Pressure differences open and close valves; the valves do not actively push. Atria top up the ventricles before the ventricles create the main pressure.
  3. The electrical triggerConnect the heart's electrical conduction system to coordinated chamber contraction and blood movement.A signal begins in the sinoatrial node, spreads across the atria, pauses at the atrioventricular node, and then activates the ventricles. Electrical activity comes first, followed by muscle pressure and valve-guided flow.
  4. The pump in contextSynthesize pulmonary and systemic circulation into one timed, repeating mechanism.The lungs link the right and left pumps. The thicker-walled left ventricle drives the longer body circuit, while the electrical system, chambers, pressure gradients, and valves keep both circuits moving in sequence.

Questions this course answers

Which chamber sends oxygen-poor blood toward the lungs?

The right ventricle ejects blood through the pulmonary valve into the pulmonary artery, which carries it to the lungs.

Put the blood-flow stages in order, starting with blood returning from the body.

The right heart handles the lung-bound leg first; after gas exchange, the left heart handles the body-bound leg.

Match each structure with its role in the pump.

Each part contributes a different job: receiving, pressure generation, one-way control, or separation of the two circuits.

Why must the electrical signal reach the atria before the ventricles?

The sequence preserves the pump's receiving phase before its main pressure-generating phase.

Grounded in trusted sources

  • National Heart, Lung, and Blood Institute, How the Heart Works, https://www.nhlbi.nih.gov/health/heart
  • National Heart, Lung, and Blood Institute, How Blood Flows through the Heart, https://www.nhlbi.nih.gov/health/heart/blood-flow
  • OpenStax, Anatomy and Physiology 2e, 19.3 Cardiac Cycle, https://openstax.org/books/anatomy-and-physiology-2e/pages/19-3-cardiac-cycle
  • American Heart Association, Heart Valves and Circulation, https://www.heart.org/en/health-topics/heart-valve-problems-and-disease/about-heart-valves
  • NCBI Bookshelf, In brief: How does the heart work?, https://www.ncbi.nlm.nih.gov/books/NBK279249/

Every Wunder lesson is built from real, reputable sources — never invented.

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