Birds have a duodenum and stomach similar to humans, but they also have an extra organ at this stage indigestion, the gizzard. The gizzard is similar to the stomach, but it is disc-shaped and very muscular. It is responsible for breaking down food. Because of this, it sometimes contains small stones to help grind the food. A cycle of contractions forces food back and forward between the stomach, gizzard, and duodenum to help mix it with enzymes. The small intestine of birds is very similar to that of humans. It is responsible for absorbing nutrients and does so with the aid of the same enzyme as in humans, produced, produced by the pancreas.The human large intestine is also known as the colon. It is much shorter and fatter than the small intestine-about 1m long and 6cm in diameter. All the useful material in food is absorbed before it reaches the large intestine.Only waste material and water, containing dissolved mineral salts, is left. The main function of the large intestine is to remove the water and salts from the waste. It does this in the same way as the small intestine absorbs nutrients.Once the water and mineral salts have been removed, the waste material becomes more solid, eventually forming the brown waste material called feces. Feces are stored in the rectum until they are excreted through the anus.
