Your pulse matches your heartbeat because arteries expand with each contraction of the heart.

The longer version

Arteries widen slightly with each surge of blood because their walls contain elastic tissue. When the heart's main chamber contracts, it pushes a volume of blood into the aorta faster than it can drain away downstream, so the wall stretches and a pressure wave travels along the vessel.

That wave moves faster than the blood itself and can be felt wherever a large artery lies close to the surface, such as the wrist or neck. As the wave passes, the vessel recoils, which smooths the flow between beats. Stiffer vessels transmit the wave differently, which is why pulse character changes with age. Counting these expansions therefore gives the same number as counting the contractions.

Where this entry sits

These facts look at how the human body works in ordinary moments, from breathing and blinking to balance and sleep. They focus on anatomy, senses, and small reactions that happen constantly without any conscious effort. The full list sits on the Human Body page, where every entry is listed in order.