Which anatomical system of an organism introduces respiratory gases to the interior of the body and enables gas exchange?
a. Excretory
b. Endocrine
c. Respiratory
d. None of the above
The correct answer and explanation is :
Correct Answer: c. Respiratory
The respiratory system is the anatomical system responsible for introducing respiratory gases — mainly oxygen (O₂) and carbon dioxide (CO₂) — into and out of the body. This system plays a vital role in maintaining cellular respiration, which is the process by which cells generate energy in the form of ATP (adenosine triphosphate). Oxygen is required by cells to efficiently produce ATP through aerobic respiration, while carbon dioxide is a waste product that must be expelled.
The major organs of the respiratory system include the nose, pharynx, larynx, trachea, bronchi, and lungs. When we inhale, air enters through the nose or mouth, passes down the trachea, and moves into the bronchi, which branch into smaller bronchioles within the lungs. At the end of these bronchioles are tiny air sacs called alveoli, which are the primary site of gas exchange.
The alveoli are surrounded by a dense network of capillaries. Here, oxygen diffuses across the thin alveolar membrane into the blood, where it binds to hemoglobin in red blood cells. Simultaneously, carbon dioxide diffuses from the blood into the alveoli to be exhaled from the body. This process is driven by differences in partial pressure of gases — a principle known as gas exchange by diffusion.
The respiratory system works closely with the circulatory system, which transports oxygen-rich blood from the lungs to tissues and returns carbon dioxide-rich blood to the lungs for removal. Without the respiratory system, oxygen could not enter the body efficiently, and carbon dioxide would build up to toxic levels.
Other systems like the excretory system (choice a) and endocrine system (choice b) serve very different roles — waste removal and hormone regulation, respectively — and do not handle respiratory gases.
Thus, the correct answer is c. Respiratory.