ISSA Nutritionist Practice Exam 2025 - Complete Preparation Guide

The main role of the respiratory system is gas exchange, which involves the intake of oxygen and the expulsion of carbon dioxide. This process occurs primarily in the lungs, where oxygen from the atmosphere is transferred into the bloodstream, and carbon dioxide, a waste product produced by metabolism, is removed from the bloodstream and exhaled.

This function is vital for sustaining life, as oxygen is essential for cellular respiration, the process by which cells produce energy. The respiratory system works closely with the cardiovascular system to ensure that oxygen is efficiently delivered to tissues throughout the body and that carbon dioxide is removed effectively.

The other options relate to different bodily systems: circulating blood is primarily the function of the cardiovascular system, digestion is associated with the digestive system, and regulating hormones falls under the endocrine system. Understanding these distinctions is essential for grasping the various roles different systems play in maintaining overall health and homeostasis.