The system that takes in oxygen and releases carbon dioxide is the respiratory system.

Here's how it works:

* Breathing: The respiratory system takes in oxygen through the lungs during inhalation.

* Gas Exchange: In the tiny air sacs of the lungs (alveoli), oxygen passes into the bloodstream, and carbon dioxide from the bloodstream passes into the alveoli.

* Exhalation: The respiratory system releases carbon dioxide from the body through exhalation.

This exchange of gases is essential for cellular respiration, the process that provides energy to our cells.