What is the primary function of the spleen in the circulatory system?

The primary function of the spleen in the circulatory system is to filter blood. The spleen plays a critical role in removing old or damaged red blood cells and filtering out pathogens and debris from the bloodstream. It contains specialized cells that identify foreign invaders, such as bacteria and viruses, and helps in the immune response by producing lymphocytes, which are essential for fighting infections.

Additionally, the spleen helps to recycle iron from hemoglobin in aged red blood cells to support the production of new red blood cells in the bone marrow. This filtering process is essential for maintaining healthy blood composition and overall body health.

The other options do not correctly describe the function of the spleen. The production of insulin is primarily a function of the pancreas, the storage of bile occurs in the gallbladder, and regulating blood pressure is mainly managed by the kidneys and blood vessels, rather than by the spleen.