Your left lung is smaller than your right — to make room for your heart
The human heart is located slightly to the left of centre in the chest. To accommodate this, the left lung has two lobes while the right lung has three, and the left lung has a concave section called the cardiac notch where the heart sits. As a result, the right lung is about 10% larger than the left and has greater respiratory capacity. The heart is not fully on the left — about two-thirds is to the left of centre and one-third to the right — but the asymmetry is enough to meaningfully affect lung size.
We think of paired organs (lungs, kidneys) as symmetric. Learning that your heart displaces one lung enough to reduce it by 10% makes internal anatomy feel like a packing problem that evolution solved pragmatically rather than elegantly.
“Your left lung is smaller than your right — it has only 2 lobes vs 3 — because your heart takes up space on the left side. Your heart is not fully on the left; it's 2/3 left, 1/3 right. 🫁 #OddlyHuman”