What is the primary function of the digestive system?

The primary function of the digestive system is to break down complex molecules into simpler forms that can be absorbed and utilized by the body's cells. This intricate process begins in the mouth, where food is mechanically and enzymatically processed, and continues in the stomach and intestines, where various enzymes and digestive juices further decompose carbohydrates, proteins, and fats. Once broken down, these nutrients are absorbed into the bloodstream through the walls of the intestines, allowing them to be transported to cells across the body for energy, growth, and repair.

The other functions listed do not accurately represent the main role of the digestive system. While storing energy is a function related to the storage of glycogen in the liver, it is not the primary role of the digestive system itself. Similarly, the regulation of hormones is primarily the responsibility of the endocrine system, not the digestive system. Lastly, the absorption of oxygen occurs in the respiratory system, through the lungs, rather than in the digestive system. Hence, the focus on breaking down complex molecules is central to understanding the essential purpose of the digestive process in overall health and nutrition.