Which system is NOT a transport system in the human body?

The digestive system is primarily responsible for the breakdown of food, absorption of nutrients, and elimination of waste from the body. While it does transport nutrients from the intestines to the bloodstream, its main function is not focused on transportation in the same way that other systems are.

The respiratory system facilitates the exchange of gases by bringing in oxygen and expelling carbon dioxide, which is a critical transport-related function. The circulatory system actively transports blood, nutrients, hormones, and waste products throughout the body, serving as the primary transportation network. The endocrine system, while not a transport system in the conventional sense, uses hormones that circulate in the blood to deliver messages and regulate body functions, thereby also playing a role in the transport of chemical signals.

The emphasis on the distinct functions of transporting versus processing food highlights why the digestive system is correctly identified as the one that does not fit within the same category as the others when considering transport systems in the human body.