Final answer:
A normal spleen's long dimensions should not exceed 12 cm (5 inches). It functions as a blood filter and plays a role in immune responses.
Step-by-step explanation:
A normal spleen's long dimensions should not exceed 12 cm (5 in). The spleen, a secondary lymphoid organ, is crucial for filtering blood and is involved in both immune responses and the removal of old red blood cells. The spleen is described as a fragile organ with a rich vascularization, making it appear dark red. Its significant vascularization, along with macrophages and dendritic cells, enables the spleen to act as a 'filter of the blood'. The location of the spleen is in the upper left part of the abdomen, attached to the lateral border of the stomach via the gastrosplenic ligament.