National Academy of Sports Medicine (NASM) Performance Enhancement Specialist (PES) Certification Practice Exam 2026 - Free Practice Questions and Study Guide

The process that brings oxygen from the air, across the alveolar membrane, and into the blood to be carried by hemoglobin is best defined as external respiration. This term specifically refers to the exchange of gases between the atmosphere and the bloodstream. During external respiration, oxygen diffuses from the alveoli in the lungs into the pulmonary capillaries, where it binds to hemoglobin in red blood cells for transport throughout the body. This process is distinct from pulmonary ventilation, which involves the mechanical movement of air in and out of the lungs and does not encompass the actual gas exchange that occurs at the alveolar level.

Understanding this distinction is crucial for grasping the various components of respiratory physiology, as external respiration emphasizes the crucial role of the alveoli in facilitating oxygen transport. Additionally, cellular respiration refers to the metabolic processes that occur within cells to produce energy, while blood circulation describes the movement of blood throughout the body and is not limited to the transfer of gases.