Emergency Medical Technician (EMT) Intermediate Practice Exam

Internal respiration is defined as the:

1. Exchange of oxygen and carbon dioxide at the cellular level

2. Process of breathing in and out

3. Exchange of gases in the lungs

4. Transfer of blood between the heart and lungs

The correct answer is: Exchange of oxygen and carbon dioxide at the cellular level

Internal respiration refers specifically to the exchange of oxygen and carbon dioxide at the cellular level. This process occurs as oxygen is delivered to the cells through the bloodstream, where it is used for metabolic processes, while carbon dioxide, a waste product of metabolism, is transported back into the bloodstream to be removed from the body. This definition highlights the importance of cellular metabolism and the role of red blood cells in facilitating the transfer of these gases. During internal respiration, oxygen moves from the blood into the cells, while carbon dioxide moves from the cells into the blood, which is critical for maintaining homeostasis in the body. The other options describe different aspects of respiratory physiology. The process of breathing in and out pertains to external respiration, which is the movement of air into and out of the lungs. The exchange of gases in the lungs describes pulmonary respiration, where oxygen is taken into the blood and carbon dioxide is expelled. The transfer of blood between the heart and lungs, often referred to as pulmonary circulation, focuses on the role of the cardiovascular system rather than the cellular exchange of gases.