What is the primary function of the spleen in relation to blood?

The primary function of the spleen in relation to blood is that it stores blood. The spleen plays a vital role in the immune system and the maintenance of blood cells. One of its significant functions is the storage of red blood cells and platelets. In times of need, such as during vigorous physical activity, the spleen can release these stored cells back into circulation to enhance the blood supply. Additionally, the spleen helps filter and remove old or damaged blood cells, contributing to overall blood health.

While the spleen does have functions related to blood, it does not actively pump blood or dominate blood flow like the heart and blood vessels do. Instead, it acts more as a reserve repository for blood components, which is critical in various physiological scenarios.