Circulation — the double circuit of the human heart
Both circuits drawn as one closed loop with the pressures that make them work: right side 25/4 mmHg into the lungs, left side 120/8 into the aorta, the four valves in sequence, the SA and AV nodes that time them, and a cardiac output of 70 beats × 70 mL ≈ 4.9 L min⁻¹.
Rendering…
Make it your own.
{
"nodes": [
{ "id": "venacava", "type": "cylinder-h", "label": "Venae cavae — 75% oxygen saturated", "x": 40, "y": 40, "width": 150, "height": 104, "fill": "#dbeafe", "stroke": "#1d4ed8", "bold": true },
{ "id": "rightatrium", "type": "heart", "label": "Right atrium — 0 to 8 mmHg", "x": 215, "y": 40, "width": 150, "height": 104, "fill": "#dcfce7", "stroke": "#15803d", "bold": true },
{ "id": "tricuspid", "type": "gate", "label": "Tricuspid valve — shuts as systole starts", "x": 390, "y": 40, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1" },
{ "id": "rightventricle", "type": "heart", "label": "Right ventricle — 25/4 mmHg, thin wall", "x": 565, "y": 40, "width": 150, "height": 104, "fill": "#dcfce7", "stroke": "#15803d", "bold": true },
{ "id": "pulmonaryvalve", "type": "gate", "label": "Pulmonary valve", "x": 740, "y": 40, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1" },
{ "id": "pulmonaryartery", "type": "cylinder-h", "label": "Pulmonary artery — deoxygenated blood", "x": 915, "y": 40, "width": 150, "height": 104, "fill": "#fce7f3", "stroke": "#be185d", "bold": true },
{ "id": "capillaries", "type": "honeycomb", "label": "Systemic capillaries — O₂ unloaded", "x": 40, "y": 200, "width": 150, "height": 104, "fill": "#fef3c7", "stroke": "#b45309", "bold": true },
{ "id": "output", "type": "gauge-chart", "label": "Output = 70 min⁻¹ × 70 mL ≈ 4.9 L", "x": 215, "y": 200, "width": 150, "height": 104, "fill": "#ccfbf1", "stroke": "#0f766e", "bold": true },
{ "id": "sanode", "type": "spring", "label": "SA node — 60 to 100 impulses a minute", "x": 390, "y": 200, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1", "bold": true },
{ "id": "avnode", "type": "network-globe", "label": "AV node delays 0.1 s, then Purkinje", "x": 565, "y": 200, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1", "bold": true },
{ "id": "lungs", "type": "cloud", "label": "Pulmonary capillaries in the alveoli", "x": 740, "y": 200, "width": 150, "height": 104, "fill": "#fef3c7", "stroke": "#b45309", "bold": true },
{ "id": "gasexchange", "type": "or-junction", "label": "O₂ in, CO₂ out — leaves at 98% SaO₂", "x": 915, "y": 200, "width": 150, "height": 104, "fill": "#fef3c7", "stroke": "#b45309", "bold": true },
{ "id": "aorta", "type": "cylinder-h", "label": "Aorta — 120/80 mmHg, elastic recoil", "x": 40, "y": 360, "width": 150, "height": 104, "fill": "#dbeafe", "stroke": "#1d4ed8", "bold": true },
{ "id": "aorticvalve", "type": "gate", "label": "Aortic valve — shuts at the dicrotic notch", "x": 215, "y": 360, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1" },
{ "id": "leftventricle", "type": "heart", "label": "Left ventricle — 120/8 mmHg, thick wall", "x": 390, "y": 360, "width": 150, "height": 104, "fill": "#dcfce7", "stroke": "#15803d", "bold": true },
{ "id": "mitral", "type": "gate", "label": "Mitral valve", "x": 565, "y": 360, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1" },
{ "id": "leftatrium", "type": "heart", "label": "Left atrium — 8 to 12 mmHg", "x": 740, "y": 360, "width": 150, "height": 104, "fill": "#dcfce7", "stroke": "#15803d", "bold": true },
{ "id": "pulmonaryveins", "type": "cylinder-h", "label": "Pulmonary veins — oxygenated blood", "x": 915, "y": 360, "width": 150, "height": 104, "fill": "#dbeafe", "stroke": "#1d4ed8", "bold": true },
{ "id": "coronary", "type": "heart-pulse", "label": "Coronary arteries fill during diastole", "x": 40, "y": 520, "width": 150, "height": 104, "fill": "#dcfce7", "stroke": "#15803d" },
{ "id": "pressures", "type": "bar-chart", "label": "The right side pumps at a fifth the pressure", "x": 390, "y": 520, "width": 150, "height": 104, "fill": "#ccfbf1", "stroke": "#0f766e", "bold": true },
{ "id": "resistance", "type": "clipboard", "label": "Systemic resistance ≈ 17× pulmonary", "x": 740, "y": 520, "width": 150, "height": 104, "fill": "#f1f5f9", "stroke": "#475569" }
],
"edges": [
{ "id": "e1", "source": "venacava", "target": "rightatrium", "thickness": 2.5 },
{ "id": "e2", "source": "rightatrium", "target": "tricuspid", "thickness": 2.5 },
{ "id": "e3", "source": "tricuspid", "target": "rightventricle", "thickness": 2.5 },
{ "id": "e4", "source": "rightventricle", "target": "pulmonaryvalve", "thickness": 2.5 },
{ "id": "e5", "source": "pulmonaryvalve", "target": "pulmonaryartery", "thickness": 2.5 },
{ "id": "e6", "source": "pulmonaryartery", "target": "lungs", "thickness": 2.5 },
{ "id": "e7", "source": "lungs", "target": "gasexchange", "thickness": 2.5 },
{ "id": "e8", "source": "gasexchange", "target": "pulmonaryveins", "thickness": 2.5 },
{ "id": "e9", "source": "pulmonaryveins", "target": "leftatrium", "thickness": 2.5 },
{ "id": "e10", "source": "leftatrium", "target": "mitral", "thickness": 2.5 },
{ "id": "e11", "source": "mitral", "target": "leftventricle", "thickness": 2.5 },
{ "id": "e12", "source": "leftventricle", "target": "aorticvalve", "thickness": 2.5 },
{ "id": "e13", "source": "aorticvalve", "target": "aorta", "thickness": 2.5 },
{ "id": "e14", "source": "aorta", "target": "capillaries", "thickness": 2.5 },
{ "id": "e15", "source": "capillaries", "target": "venacava", "label": "the loop closes", "thickness": 2.5 },
{ "id": "e16", "source": "sanode", "target": "rightatrium", "label": "both atria contract", "style": "dashed" },
{ "id": "e17", "source": "sanode", "target": "avnode", "style": "dashed" },
{ "id": "e18", "source": "avnode", "target": "leftventricle", "label": "ventricles follow 0.1 s later", "style": "dashed" },
{ "id": "e19", "source": "output", "target": "leftventricle", "label": "stroke volume × rate", "style": "dashed" },
{ "id": "e20", "source": "aorta", "target": "coronary", "label": "first branches off the aorta" },
{ "id": "e21", "source": "coronary", "target": "rightatrium", "label": "coronary sinus drains here" },
{ "id": "e22", "source": "pressures", "target": "rightventricle", "style": "dashed" },
{ "id": "e23", "source": "pressures", "target": "leftventricle", "style": "dashed" },
{ "id": "e24", "source": "resistance", "target": "aorta", "label": "why the left wall is thicker", "style": "dashed" }
]
}