Advanced Placement (AP) Biology Practice Exam 2025 – Comprehensive All-in-One Resource for Exam Success!

Hormones are primarily carried throughout the body in the blood. The endocrine system produces hormones, which are chemical messengers released into the bloodstream. This allows them to travel vast distances to target organs and tissues where they exert their effects. The circulatory system provides a rapid and efficient means for hormones to be distributed throughout the body, ensuring that they can reach specific cellular receptors.

While hormones can also have effects through other mechanisms, such as local diffusion within a short distance or the potential involvement of the lymphatic system in specific contexts, the predominant and most effective method of hormone transport is through the bloodstream. Neurons, on the other hand, are involved in the nervous system's signaling mechanisms rather than hormone transport, and while the lymphatic system plays roles in immune responses and the transport of certain substances, it is not primarily responsible for carrying hormones.