Spleen: structure and function

In short: The spleen is a fist-sized organ in the upper left abdomen that filters out old and damaged red blood cells and performs important immune system tasks. Unlike the heart or liver, it’s not essential for survival, though losing it increases infection risk long-term.

In more detail: The spleen consists of red and white pulp, with the red pulp filtering blood and the white pulp rich in immune cells.

In detail

• Blood filtering: In the red pulp, old, misshapen, or damaged red blood cells are detected and broken down.
• Immune function: The white pulp contains many lymphocytes and helps fight pathogens in the blood, especially encapsulated bacteria.
• Blood reservoir: The spleen can serve as a reservoir for blood cells and release extra blood when needed, for example during heavy blood loss.
• Ruptured spleen: Due to its rich blood supply, a ruptured spleen after an accident can bleed life-threateningly and often requires emergency surgery.
• Life without a spleen: After removal, the liver and lymph nodes partially take over its tasks, but infection risk remains elevated (immunsystem-grundlagen).
• Vaccination protection: People without a spleen often need additional vaccinations against certain bacteria to offset the higher infection risk.
• Enlarged spleen: Infections, liver disease, or certain blood disorders can cause the spleen to swell, which is often only noticed during examinations (blut-zusammensetzung-und-aufgaben).