We learned today that the left ventricle's wall is way thicker than the right ventricle's, but they both just pump blood, right? Why does one side need so much more muscle?
Both ventricles pump the same volume of blood with each beat, but they push it on very different trips. The right ventricle only sends blood next door to the lungs, at about 25 mmHg, while the left ventricle drives it round the whole body at about 120 mmHg. Pushing against that much higher pressure takes more muscle, so the left wall is about three times thicker. The “Power side” chapter lets you see both walls side by side.
Accepted answer
Great question! The left ventricle pumps blood into the systemic circuit (the whole body), which has much higher resistance than the lungs. Systemic blood pressure runs around 120/80 mmHg, while pulmonary pressure is only about 25/10 mmHg. To generate that extra force, the left ventricle needs a thicker, more muscular wall.
To add a number to that: the left ventricle wall is typically about 3x thicker than the right. Same chambers, same job (pump blood), very different pressure to push against.