Which system in the body is involved in the breakdown and absorption of nutrients?

The digestive system is responsible for the breakdown and absorption of nutrients from the food we consume. This complex system involves several organs, including the mouth, stomach, and intestines, each playing a crucial role in processing food. The digestive process begins in the mouth, where enzymes in saliva start breaking down carbohydrates. As food travels through the esophagus to the stomach, it is mixed with gastric juices that continue the digestion process.

In the small intestine, the majority of nutrient absorption occurs, facilitated by villi and microvilli, which increase the surface area for absorption. The nutrients, once absorbed into the bloodstream, are then distributed to the body through the circulatory system for use in various bodily functions.

Other systems, such as the circulatory and endocrine systems, do play supportive roles in nutrient distribution and regulation but are not directly involved in the digestion and absorption process. The respiratory system focuses on gas exchange and is not related to nutrient absorption at all. Thus, the digestive system is the only option that accurately describes the system fundamentally involved in breaking down food and absorbing essential nutrients.