What body system is responsible for breaking down food into smaller molecules and absorbing nutrients?

The digestive system plays a crucial role in breaking down food into smaller molecules and absorbing the necessary nutrients for the body to function. This system encompasses various organs such as the mouth, esophagus, stomach, intestines, liver, and pancreas, each contributing to the process of digestion.

When food enters the mouth, it is mechanically broken down by chewing and mixed with saliva, which begins the chemical process of digestion. As food travels down the esophagus into the stomach, it is subjected to further breakdown through chemical means, particularly through the action of stomach acids and enzymes. The digestive steps continue in the small intestine, where the majority of nutrient absorption occurs. Here, enzymes from the pancreas and bile from the liver assist in digesting food into its fundamental components—carbohydrates, proteins, and fats—which can then be absorbed into the bloodstream.

The other body systems listed do not have the primary function of food breakdown and nutrient absorption. The muscular system is primarily involved in movement and support, the endocrine system regulates bodily functions through hormones, and the circulatory system is responsible for transporting nutrients, gases, and wastes throughout the body. Thus, the digestive system is distinctly and specifically responsible for the processes involved in digestion and nutrient absorption.