Circulation
The heart, arteries and veins in 3D, and the routes hormones take through them. Drag to rotate, scroll or pinch to zoom, and click any vessel to learn about it.
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Oxygen-rich blood
Oxygen-poor blood
Portal (gut → liver)
Hormone gland
3D models: BodyParts3D, © The Database Center for Life Science, licensed under CC Attribution 4.0 International (meshes simplified for the web). The model is male and does not include the thyroid gland, ovaries, the brain's venous sinuses or the tiny pituitary portal vessels; hormone routes describe those steps in words. Colours follow the textbook convention (red oxygen-rich, blue oxygen-poor), so the pulmonary arteries are blue and pulmonary veins red. Notes are for general education, not medical advice.