What do feces consist of?

Feces primarily consist of a semi-solid mass of waste products that have formed in the colon after digestion and absorption in the intestines. During the digestive process, nutrients from the food are absorbed, leaving behind waste material that includes undigested food particles, bacteria, cells shed from the intestinal lining, and various metabolic byproducts. The colon's role is to reabsorb water and salts from this waste material, resulting in the formation of feces, which is ultimately expelled from the body.

This composition highlights why feces are not merely a mixture of undigested food and nutrients, as there are also other components involved, such as bacteria and waste products. Additionally, the other choices related to liquid waste and excess fluids from the kidneys pertain more to urine production rather than the solid waste that constitutes feces.