Education example

The human heart, part by part

A rich illustration under invisible regions: each part opens a panel, numbered along the blood's path.

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In words

Everything on this diagram

The same content as the picture, as text: every part and what it says when you open it.

Superior vena cava

Brings oxygen-poor blood from the head, neck, arms and upper chest into the right atrium.

Blood: Oxygen-poor
Flows into: Right atrium
Blood flow: Step 1 of 12

Inferior vena cava

Brings oxygen-poor blood from the lower body into the right atrium. It is the largest vein in the body.

Blood: Oxygen-poor
Flows into: Right atrium
Blood flow: Step 1 of 12

Right atrium

Collects oxygen-poor blood returning from the body and passes it down through the tricuspid valve.

Blood: Oxygen-poor
Receives from: The venae cavae
Passes to: Right ventricle
Blood flow: Step 2 of 12

Tricuspid valve

Three leaflets between the right atrium and the right ventricle. It shuts as the ventricle contracts, so blood cannot flow back.

Leaflets: Three
Between: Right atrium and right ventricle
Blood flow: Step 3 of 12

Right ventricle

Pumps oxygen-poor blood out to the lungs. Its wall is thinner than the left ventricle's, because the lungs need much less pressure than the whole body.

Blood: Oxygen-poor
Pumps to: The lungs
Blood flow: Step 4 of 12

Pulmonary valve

Guards the way out of the right ventricle into the pulmonary artery, and closes so blood cannot slide back.

Cusps: Three
Between: Right ventricle and pulmonary artery
Blood flow: Step 5 of 12

Pulmonary artery

Carries blood from the right ventricle to both lungs, where it picks up oxygen. Unusually for an artery, the blood in it is oxygen-poor.

Blood: Oxygen-poor
Divides into: Left and right branches
Blood flow: Step 6 of 12

Pulmonary veins

Bring oxygen-rich blood back from the lungs into the left atrium. There are usually four, two from each lung; the pair from the right lung runs behind the heart and is hidden here.

Blood: Oxygen-rich
Usually: Four
Blood flow: Step 7 of 12

Left atrium

Collects oxygen-rich blood from the lungs and passes it down through the mitral valve.

Blood: Oxygen-rich
Receives from: Pulmonary veins
Passes to: Left ventricle
Blood flow: Step 8 of 12

Mitral valve

Two leaflets between the left atrium and the left ventricle, which is why it is also called the bicuspid valve.

Leaflets: Two
Also called: Bicuspid valve
Blood flow: Step 9 of 12

Left ventricle

The heart's main pump. Its thick muscular wall drives oxygen-rich blood out through the aorta to the whole body.

Blood: Oxygen-rich
Pumps to: The whole body
Blood flow: Step 10 of 12

Aortic valve

Opens as the left ventricle contracts and closes behind each beat, so blood cannot return from the aorta.

Cusps: Three
Between: Left ventricle and aorta
Blood flow: Step 11 of 12

Aorta

The body's largest artery. It rises from the left ventricle, arches over the heart, and carries oxygen-rich blood on to every organ.

Blood: Oxygen-rich
Shape: Ascends, arches, then descends
Blood flow: Step 12 of 12

Septum

The muscular wall between the left and right sides, which keeps oxygen-rich and oxygen-poor blood apart.

Separates: Left and right sides

Myocardium

The heart muscle itself, which contracts with every beat. It is fed by its own coronary arteries, which run over its outer surface.

Made of: Cardiac muscle
Thickest at: The left ventricle

Sinoatrial (SA) node

The heart's natural pacemaker, in the wall of the right atrium. Each heartbeat starts here as an electrical signal.

Role: Natural pacemaker
Signal order: 1 of 3

Atrioventricular (AV) node

Holds the signal for a moment, so the atria finish emptying before the ventricles contract.

Role: Brief delay
Signal order: 2 of 3

Bundle of His and Purkinje fibres

Carry the signal down the septum and out through the ventricle walls, so the ventricles squeeze from the bottom up.

Role: Spread the signal
Signal order: 3 of 3