What is the primary role of the spleen?

The primary role of the spleen is to filter and store blood cells. It functions as part of the lymphatic system and plays several critical roles in the maintenance of blood health. The spleen filters out old or damaged red blood cells and helps in the recycling of iron from hemoglobin. Additionally, it plays a role in the immune system by containing white blood cells that help fight infections. This filtering process ensures that the blood cells in circulation are healthy and functional, which is crucial for overall bodily health. The storage aspect comes from the spleen's ability to hold a reserve of red blood cells and platelets that can be released into the bloodstream when needed, such as in cases of bleeding or increased exercise demand.

The other options describe functions that are not associated with the spleen. For instance, bile production is a function of the liver, storing excess fat is not a role of any organ but instead refers to overall body fat storage, and hormone regulation involves glands such as the pancreas and thyroid, not the spleen. Understanding the specific functions of each organ helps clarify their individual roles in the body's overall physiology.