Final answer:
The spleen is a major secondary lymphoid organ that acts as a filter of the blood. It functions in immune responses and removes microbes from the blood. However, the percentage of normal adults with a palpable spleen tip is not provided in the given information.
Step-by-step explanation:
The spleen is about 12 cm long and acts as a major secondary lymphoid organ in the human body. It functions as a filter of the blood by removing microbes and dying red blood cells. Additionally, the spleen plays a role in immune responses to blood-borne pathogens.
However, the percentage of normal adults with a palpable spleen tip varies and is not provided in the given information.