Final answer:
The spleen's role in fetal life includes blood cell production known as extramedullary hematopoiesis and filtering the blood by removing microbes and dying red blood cells. It also contributes to mounting immune responses to blood-borne pathogens.
Step-by-step explanation:
The role of the spleen in fetal life is significantly different from its function in an adult. During fetal development, the spleen is involved in producing blood cells, a process known as extramedullary hematopoiesis. Initially, blood cells are made in the yolk sac, but as the embryo develops, this responsibility is transferred to the spleen, lymph nodes, and liver. Eventually, the bone marrow becomes the primary site for hematopoiesis, although the spleen and other organs can retain a hematopoietic role if needed, such as in cases of bone marrow failure. In addition to hematopoiesis, the fetal spleen also acts as a filter for the blood, removing microbes, other materials, and dying red blood cells with the help of macrophages and dendritic cells. It is also a key organ involved in mounting immune responses to blood-borne pathogens, due to its role as a secondary lymphoid organ.