Illustration of the the liver, gallbladder, stomach, pancreas, spleen, and selected vasculature of the region. The largest internal organ, the liver regulates chemical levels in the blood and excretes the bile that helps remove waste products. The gallbladder collects and concentrates digestive bile produced by the liver. The stomach churns food through its muscular layers. The pancreas produces an exocrine secretion that neutralizes acid and secretes the hormones the insulin and glucagon. And the spleen stores blood, disintegrates old blood cells, filter foreign substances from the blood, and produce lymphocytes.