What is an animal gut?

An animal gut or digestive system is a series of organs that convert food into energy and basic nutrients to feed the entire body. The digestive system starts with the mouth, also called the oral cavity, where food first enters the body and is broken down by chewing and saliva. It continues through the esophagus, a muscular tube that carries food to the stomach. The stomach, a muscular sac that secretes gastric juice, breaks down the food further until it becomes a semi-liquid substance known as chyme.

From the stomach, chyme moves into the small intestine, which is the longest and most complex part of the digestive system. Here, the majority of nutrient absorption takes place as chyme is mixed with digestive enzymes produced by the pancreas, such as amylase, lipase, and protease, and bile produced by the liver. These enzymes break down complex carbohydrates, fats, and proteins into simple sugars, fatty acids, and amino acids, respectively. The walls of the small intestine contain tiny, finger-like projections called villi that increase the surface area for nutrient absorption.

The undigested material left after nutrient absorption moves into the large intestine, which consists of the colon and rectum. The colon absorbs water and electrolytes, converting the remaining chyme into solid waste. The rectum stores the solid waste until it can be eliminated from the body through the anus during the process of defecation.