Light micrograph of a section through an appendix showing chronic appendicitis. The appendix is a small branch of the large intestine that has no function in humans. Here, the cavity of the appendix is blocked and inflamed with fat cells (white) and fibrous tissue (purple). The inflammation has attracted white blood cells (dark blue), part of the body's immune response. The white blood cells further block the area, causing it to become infected. If the appendix bursts, the inner wall of the abdomen may also become infected. Appendectomy, or removal of the appendix is the common treatment.