In human physiology, what is the main purpose of the respiratory system?

• A. To secrete hormones that regulate metabolism and maintain long-term homeostasis
• B. To transport oxygen and nutrients through the body via the heart and blood vessels
• C. To exchange gases by bringing $O_2$ into the body and removing ${\mathrm{CO}}_2$
• D. To filter metabolic wastes from the blood and regulate urine production

Answer: (C)

Verified step by step guidance

1. Step 1: Identify the primary function of the respiratory system by understanding its role in human physiology, which involves the movement of gases between the external environment and the body's cells.
2. Step 2: Recognize that the respiratory system is responsible for bringing oxygen (O\_2) into the body, which is essential for cellular respiration and energy production.
3. Step 3: Understand that the respiratory system also removes carbon dioxide (CO\_2), a waste product of metabolism, from the body to maintain acid-base balance and prevent toxicity.
4. Step 4: Differentiate the respiratory system's function from other systems, such as the endocrine system (hormone secretion), cardiovascular system (transport of oxygen and nutrients), and urinary system (waste filtration and urine production).
5. Step 5: Conclude that the main purpose of the respiratory system is to exchange gases by bringing O\_2 into the body and removing CO\_2, which is critical for maintaining homeostasis and supporting cellular functions.