Which digestive organ is involved in reabsorbing water to form stool?

The colon, also known as the large intestine, plays a crucial role in the reabsorption of water from undigested food material. As the leftovers from digestion pass through the intestines, the colon extracts water and salts, thereby transforming the semi-liquid waste into a more solid form, or stool. This process is vital for maintaining the body's fluid balance and preventing dehydration.

By the time the waste reaches the colon, it has already gone through the stomach and small intestine, where most nutrients and a smaller portion of water absorption occurs. However, it is in the colon where the majority of water reabsorption takes place. The colon also helps to compact the waste into feces before it is expelled from the body. Thus, its primary function of reabsorbing water makes it the key digestive organ involved in forming stool.