Final answer:
The spleen is located in the left upper quadrant of the abdomen and is attached to the stomach. It functions to filter pathogens and old red blood cells from the blood, with lymphocytes destroying them in the spleen.
Step-by-step explanation:
The spleen is located in the left upper quadrant of the abdomen. It is a major secondary lymphoid organ that is approximately 12 cm (5 in) long, attached to the lateral border of the stomach via the gastrosplenic ligament. Functionally, the spleen acts as a filter for the blood, capturing pathogens and worn-out red blood cells, which are then destroyed by lymphocytes present in the spleen. This organ is situated just inferior to the diaphragm in the upper-left quadrant of the abdominopelvic cavity, making it prone to referred pain during conditions like a splenic rupture, which can be indicated by Kehr's sign due to diaphragmatic irritation.