INTERACTIVE EXPLANATION

Where does your blood go after a heartbeat?

Turn a real anatomical model in your hands. Reveal its chambers, meet the four valves, then follow the blood moving through both sides of the heart.

Enable JavaScript to change the conditions and run the interactive experiment.

Make a discovery

The right side sends blood to the lungs. The left side sends it to the body. These are connected loops, with valves helping maintain one-way flow. Artery means away from the heart—not necessarily oxygen-rich.

Make a prediction

Does blood in the pulmonary artery have to be oxygen-rich because it is in an artery?

Yes, all arteries carry oxygen-rich blood
No, artery describes direction from the heart

Read the explanation

The pulmonary arteries take relatively oxygen-poor blood from the right ventricle toward the lungs. Pulmonary veins bring oxygen-rich blood back to the left atrium.

Understand it

Trace both loops

Body → venae cavae → right atrium → tricuspid valve → right ventricle → pulmonary valve and arteries → lungs → pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve and aorta → body. The 3D model preserves the atlas geometry; the study diagram unfolds these connections to make the complete route easier to follow.

Watch the pressure gates

Valves open or close passively as pressure differences change. During ventricular filling the atrioventricular valves are open. During ejection the outlet valves are open. There are short phases when both sets are closed: pressure changes while ventricular volume is nearly constant.

Two sides act together

Both ventricles contract during the same overall cycle. In a steady circulation their average outputs match; the right and left outputs are not added together when reporting cardiac output. The simplified cycle omits fine differences in left/right timing.

Look closer at the science

Rate × amount per beat

Cardiac output per ventricle = heart rate × stroke volume. For the illustrative 75 beats/min and 70 mL/beat, the result is 5.25 L/min. The controls are independent arithmetic comparisons, not a prediction of an individual person.

Systole and diastole

Systole means contraction; diastole means relaxation. The valve view uses five ordered phases: filling, atrial contraction, isovolumetric contraction, ejection, isovolumetric relaxation. Their proportions are illustrative and fixed, not a clinical pressure trace or ECG.

A model’s missing feedback

In a body, filling time, venous return, contractility and vascular resistance interact. Raising rate indefinitely does not keep raising output at a fixed stroke volume. This lesson has no disease, exercise, blood-pressure or oxygen-saturation prediction.

Try it yourself: Notice a pulse. Trace its source.

Supplies

A comfortable place to sit
A clock with seconds
Paper and a pencil

Find the gentle beat
Sit comfortably. Rest the index and middle fingers lightly on the underside of your other wrist, below the base of the thumb. If you do not find a pulse easily, skip counting and use the route drawing instead.
Count and record
Without changing your breathing or doing exercise, count beats for 60 seconds. Record the count and the observation time. This is an observation, not a score or a health test.
Follow the connection
Draw left ventricle → aorta → arm artery → wrist. Then trace the return route and lung loop in the lesson. A pulse is a traveling pressure disturbance, not a single blood cell traveling from heart to wrist on each beat.

Can you connect a pulse at your wrist to the heart’s left ventricle?

No neck-pressure, exercise or breath-holding activity. Counts vary and are not interpreted here. These illustrations do not provide medical assessment.

Sources and model limits

The 3D surfaces come from the BodyParts3D adult male anatomical atlas. They are curated reference geometry, not a patient scan. Chamber cavities are casts of blood spaces, not extra tissue layers. The ventricular wall is one unified piece. Teardown offsets separate three wall pieces for teaching; they are not physical heart motion.
Moving marks indicate flow direction along illustrative paths between anatomical landmarks. Motion through each valve is gated by its open phase; venous return is illustrative. No individual cell, transit time, flow velocity or conserved particle count is simulated. The source valve leaflets remain in their reference pose; their highlights indicate timing, not mesh deformation.
The valve sequence plays at one fifth of the selected heartbeat rate. Only the separate study diagram uses qualitative chamber pulsation; the anatomical surfaces retain their source shape. Stroke volume affects output arithmetic only; visual chamber size is not a volume measurement.
Color is a key for relatively oxygen-poor/rich blood; all human blood is red. Coronary circulation, vessel compliance and gas-exchange rates are omitted.

The model’s original surfaces and named structures come from the BodyParts3D anatomical atlas.

DBCLS BodyParts3D 4.0 polygon-reduced OBJ data. Original relative coordinates and triangles are retained, reoriented together and converted to GLB. Teaching colors, exploded offsets, selection and flow markers are Brytalearn additions.

DBCLS · BodyParts3D

The four chambers, septum, major vessels and valves have distinct roles and anatomical positions.

NHLBI, How the Heart Works: What the Heart Looks Like. Supports the chamber and vessel explanations alongside the original atlas labels.

NHLBI · Heart anatomy

Arteries carry blood away; veins return it. Four valves maintain directed flow through two linked circulation loops.

NHLBI, How Blood Flows through the Heart, Heart valves and Blood flow sections. Supports route connectivity and oxygen-label convention.

NHLBI · Blood flow

Pressure differences govern valve transitions, including phases when both inlet and outlet valves are closed.

Anatomy and Physiology 2e §19.3, Pressures and Flow; Phases of the Cardiac Cycle. The implementation uses five qualitative phases with illustrative normalized durations.

OpenStax · Cardiac cycle

Cardiac output is rate × stroke volume for each ventricle.

Anatomy and Physiology 2e §19.4, Resting Cardiac Output. The 75 × 70 reference is an example, not a recommended or diagnostic range.

OpenStax · Cardiac output

A wrist pulse can be observed with index and middle fingers.

MedlinePlus Pulse, How the Test Is Performed. Home activity omits clinical interpretation and reference ranges.

MedlinePlus · Pulse

Independent subject review is pending.

Read the sources and model assumptions