Visual Biology Lesson

The Human Heart

Meet the pump inside your chest. Explore its parts, follow the blood, and test what you learn.

Interactive diagramBlood-flow modelInstant-feedback quiz

Explore the heart

The heart is a strong muscle that works like a pump. Its right side sends blood to the lungs. Its left side sends blood to the rest of the body.

☝Your task: Select a coloured heart part or its name. Read its job, then continue to the blood-flow pathway.

Interactive cross-section of the human heart Educational cross-section showing the four chambers, septum, valves and major vessels. Blue indicates oxygen-poor blood, red indicates oxygen-rich blood, and arrows show the direction of flow. RIGHT ATRIUMRIGHT VENTRICLE LEFT ATRIUMLEFT VENTRICLE SEPTUM Vena cava Right atrium Right ventricle Aorta Pulmonary vein Left atrium Left ventricle Septum

Diagram view: the heart’s right side appears on your left. Colours show oxygen level, not whether a vessel is an artery or vein.

Oxygen-rich bloodOxygen-poor blood
Start here

Choose a heart part

Tap a coloured area of the heart or choose a name below. You will see what that part does.

Remember: The heart’s right side appears on your left when you look at this diagram.

0 of 10 parts explored

The blood pathway

Blood travels through the heart in one direction. Valves stop it from flowing backwards.

1

Body → right side

Oxygen-poor blood returns through the vena cava to the right atrium, then moves into the right ventricle.

2

Heart → lungs

The right ventricle pumps this blood through the pulmonary artery to the lungs.

3

Lungs → left side

Oxygen-rich blood returns through the pulmonary veins to the left atrium, then moves into the left ventricle.

4

Heart → body

The left ventricle pumps this blood through the aorta to the whole body.

Oxygen-poor and oxygen-rich pathways

The two pathways connect at the lungs. Blue tracks show oxygen-poor blood travelling to the lungs; red tracks show oxygen-rich blood travelling from the lungs to the body.

Oxygen-poor blood

Returning from body tissues, this blood needs oxygen.

  1. Vena cava
  2. Right atrium → right ventricle
  3. Pulmonary artery
  4. Lungs: picks up oxygen

Oxygen-rich blood

After the lungs, this blood is ready for the body.

  1. Pulmonary veins
  2. Left atrium → left ventricle
  3. Aorta
  4. Body: delivers oxygen

Blue = oxygen-poor; red = oxygen-rich. The colors describe oxygen level, not artery versus vein.

Blood-flow sequence challenge

Use the flashcard to learn one step, then choose what comes next. The sequence follows blood from the body and back again.

1

Body → right atrium

Oxygen-poor blood returns from the body through the vena cava.

Remember: The right side sends blood to the lungs.

What happens next?

Choose the next step in the pathway.

Compare the two sides

Left side of the heart

  • Receives oxygen-rich blood from the lungs.
  • Pumps blood around the whole body.
  • Its ventricle has a thicker wall because it must push blood farther.

Right side of the heart

  • Receives oxygen-poor blood from the body.
  • Pumps blood to the nearby lungs.
  • Its ventricle has a thinner wall because it pushes blood a shorter distance.

Check your understanding

Question 1 of 6