Heart, Blood & Breath
Circulation and gas exchange end to end: the heart’s electrical conduction and pump cycle, pressure held by the baroreflex and the renin–angiotensin system, clotting and its breakdown, and the lung mechanics that load oxygen onto haemoglobin and release it in tissue. The blood’s own components — red cells, platelets, lipoproteins, iron and ABO type — are animated beside them.
Every page here is a hands-on animated diagram, not a video — press play, slow it down, break the mechanism on purpose, and read the live values in real clinical units. They explain how a process works; they are not medical advice, and the evidence for any treatment lives on the topic pages each animation links into.
Table of Contents
The Animations (24)
Surfactant: Why Your Lungs Don’t Collapse
See why 300 million wet air-sacs don’t collapse from surface tension — a soapy surfactant holds them open — then take it away, as in a premature baby, and watch the lungs stiffen and collapse.
Launch animation →Potassium & the Heartbeat
Slide your blood potassium up and down and watch the ECG morph in real time — peaked T waves and a widening QRS as it climbs, U waves and a stretched QT as it falls — with an alarm at the danger lines and a beating heart that hears every one.
Launch animation →Blood pH: The Acid–Base Balancing Act
Hold your blood pH on a knife-edge between 7.35 and 7.45 — blow off CO₂ with the lungs in minutes, dump acid through the kidneys over hours, then break it with hyperventilation or diabetic ketoacidosis.
Launch animation →How Your Body Makes Red Blood Cells (EPO)
Watch the kidney sense low oxygen and fire EPO at the bone marrow to build red cells — then climb a mountain to surge it, lose it in kidney disease, or dope with it and thicken the blood.
Launch animation →Hemoglobin & the Oxygen Dissociation Curve
Load oxygen onto hemoglobin one cooperative step at a time to draw the famous S-curve — then shift it with exercise, watch carbon monoxide lock it shut, or switch to fetal hemoglobin pulling O₂ from mom.
Launch animation →The Lymphatic System: Your Body’s Drainage & Surveillance
Watch the fluid your blood leaks get collected, squeezed along by moving muscles through one-way valves and filtering lymph nodes, and returned to the blood — then block a node and watch the limb swell.
Launch animation →Iron & the Hepcidin Gate
Watch vitamin C unlock plant iron and hepcidin slam the gate shut — then add inflammation and see why a high ferritin can still mean too little usable iron.
Launch animation →How Blood Clots Dissolve — Fibrinolysis & Clot-Busters
Once the vessel heals, watch plasmin snip the fibrin mesh strand by strand and D-dimer wash away — then add a tPA clot-buster to blast it, or tranexamic acid to hold it shut.
Launch animation →Cholesterol & the Artery Wall
Follow LDL particles into the artery wall and watch foam cells build a plaque — then add a statin and see the liver's receptors pull them back out.
Launch animation →How Blood Gets Back to the Heart
Squeeze the calf-muscle pump and watch one-way valves march blood uphill against gravity — then let a valve fail and see blood pool backwards into a bulging varicose vein.
Launch animation →Breathing & Gas Exchange
Move the diaphragm, fill the alveoli, and watch oxygen diffuse into the blood while carbon dioxide leaves — with live pO₂/pCO₂ meters and an exercise mode.
Launch animation →Your Airway’s Self-Cleaning Escalator (& the Cough)
Watch millions of cilia sweep a mucus blanket of trapped dust and germs up and out of your lungs — then trigger a cough to blast an irritant clear, or light a cigarette and watch the escalator freeze.
Launch animation →Nitric Oxide & Vessel Dilation
Watch the endothelium turn L-arginine into nitric oxide, relax the artery wall, and widen the lumen — then let oxidative stress uncouple eNOS and see the vessel stiffen, or pour in beet nitrate to rescue it.
Launch animation →How Blood Clots
Cut the vessel and watch platelets plug it while the coagulation cascade explodes into a fibrin mesh — then take warfarin and see the vitamin-K factors go dark one by one.
Launch animation →Asthma: What Happens in an Attack
Squeeze a bronchiole shut and watch the resistance explode — halve the radius and it takes sixteen times the push — then fire a rescue inhaler and pull the peak flow back out of the red zone.
Launch animation →Blood Types: ABO, Rh & Why Transfusions Must Match
Transfuse blood and watch a match flow safely while a mismatch clumps and bursts — then see why O-negative is the universal donor and how a RhoGAM shot protects a second Rh-positive baby.
Launch animation →The Baroreflex: Your Blood Pressure’s Split-Second Autopilot
Stand up and watch your blood pressure dip, then get caught in a heartbeat by the baroreceptors and brainstem — or trip a vasovagal faint and see why passing out actually rescues the brain.
Launch animation →The Heart’s Electrical System & the ECG
Follow the spark from the SA-node pacemaker across the atria, through the AV-node pause, and down the fast fibres to fire the ventricles — read it live on the ECG, then break it into heart block or fibrillation.
Launch animation →Platelets: The First Responders to a Cut
Watch platelets stick, turn spiky, and pile into a plug seconds after a cut — then take aspirin and see the plug weaken, and finally sort out how antiplatelets differ from blood thinners.
Launch animation →Sleep Apnea: Why Breathing Stops at Night
Watch the throat collapse as sleep deepens, the chest keep heaving against a shut airway and the oxygen trace slide into the 80s — then switch on CPAP and see the whole night go quiet.
Launch animation →How a Pulse Oximeter Reads Your Oxygen
See how a finger clip reads your blood oxygen with two colours of light — measuring only the pulsing artery signal — and why it can read dangerously normal in carbon-monoxide poisoning.
Launch animation →Blood Pressure Control
Watch the kidney fire renin, angiotensin clamp the arteries, and aldosterone hold on to sodium — then eat salt, get dehydrated, or take an ACE inhibitor.
Launch animation →The Heart & Circulation
Trace a blood cell through all four chambers and both circuits, changing colour from blue to red in the lungs — with a live ECG, chamber pressures, and an exercise mode.
Launch animation →How Heart Failure Develops
Weaken the pump and watch the ejection fraction fall, fluid back up into the lungs, and the body's own 'fixes' (RAAS, adrenaline) quietly make it worse — then unload it with the right drugs.
Launch animation →