What is the primary function of the spleen?

The primary function of the spleen encompasses several key roles, one of which is the disposal of worn-out red blood cells. As blood circulates through the body, red blood cells have a lifespan of about 120 days. The spleen acts like a filter, identifying and removing these aged cells from circulation. This process helps maintain healthy blood composition and function, as red blood cells that are no longer effective can potentially cause complications if they remain in the bloodstream.

Additionally, the spleen also plays important roles in immune function by producing lymphocytes, which are crucial for the body's defense against pathogens. While it does store blood, including platelets, these roles are secondary to its function in the removal of defective red blood cells. Thus, while the spleen has multiple important functions, its predominant role is the disposal of worn-out red blood cells, ensuring the efficiency and health of the circulatory system.