Back to the experimentTHE EVIDENCE BEHIND THE EXPERIENCE

Two pumps. One connected circulation.: sources & model

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.

Scientific review · independent subject review pending

The source and model records are available for inspection. No external scientific reviewer has signed off yet.

circulation-3 · content 4 · setup format 1

What supports the explanation?

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

What this model assumes

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.
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.

What has been checked

Analytical reference cases, conservation or transition invariants, finite drawing commands, bounded setup parsing, discovery and route integrity are checked automatically. These checks do not establish anatomical fidelity, learner outcomes or browser/device compatibility. Independent subject review, learner trials, comprehensive accessibility review and browser video encoding checks remain pending.

Each source supports the associated claim. Sources do not certify this implementation or its visuals.

The anatomical model

The heart, airways and rib cage use original surfaces from BodyParts3D, the anatomical atlas produced by the Database Center for Life Science (DBCLS). The adult male reference began with MRI-based body geometry and was refined using anatomical references. It is a curated atlas, not a photograph or a patient-specific scan.

The chest context includes the trachea, main bronchi and 18 segmental bronchial-tree pieces within the rib cage. These branching air passages are not outer lung surfaces. The lungs’ outer boundaries and alveoli are not included in this source selection.

What is original, and what we added

We converted the version 4.0 polygon-reduced OBJ surfaces to GLB. The source triangles and relative positions are retained. All parts share one coordinate transformation and scale; we do not reposition individual organs to assemble the resting model. Colors, lighting, selection, camera controls, exploded offsets and flow markers are our teaching presentation.

The teardown moves three source wall pieces: the right atrial wall, left atrial wall and the unified ventricular wall. The colored chamber interiors are casts of blood-filled spaces. They are not another tissue layer. The source does not provide a separate movable wall for each ventricle.

The eleven source valve leaflets remain in their reference pose. Their highlighting follows a simplified cardiac cycle. Gold markers connect anatomical landmarks, but their paths and timing are illustrative; they are not measurements of blood-cell trajectories or a fluid simulation. The two-dimensional study diagram explains the complete circulation and qualitative valve motion separately.

Selected proximal vessels are shown with their source segment boundaries. Fine vessels, coronary circulation, chordae, the pericardium, disease changes and individual anatomical variation are outside this focused display.

License and attribution

The archive’s current license notice specifies CC BY 4.0. Older OBJ header comments retain the former license wording; this distribution follows the archive’s current notice. Our conversions and presentation changes are listed above. Neither DBCLS nor NHLBI endorses this implementation.

Original dataset downloads ↗ · Inspect the part IDs, source archives and file checksums ↗

About the cover illustration

The topic card is a rendering of the same BodyParts3D meshes used in the interactive model. It shows the three wall pieces separated, with teaching colors. The anatomical source and license are recorded above.

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