Kaplan Nursing Entrance Exam Practice 2026 – Comprehensive Prep

Red blood cells travel through capillaries in single file due to their biconcave shape and the narrow diameter of these small blood vessels. Capillaries are the smallest blood vessels in the circulatory system, often only wide enough for a single red blood cell to pass through at a time. This allows for efficient exchange of oxygen, carbon dioxide, nutrients, and waste products with the surrounding tissues.

The single-file arrangement maximizes the surface area contact between the red blood cells and the capillary walls, facilitating efficient gas diffusion. When red blood cells travel through capillaries, they deform slightly to fit through the tight spaces while maintaining their ability to transport hemoglobin, which carries oxygen throughout the body. This process is essential for ensuring that all tissues receive an adequate supply of oxygen.

The other scenarios suggested—traveling in groups, clumps, or the idea that red blood cells do not travel through capillaries—do not accurately reflect how these cells behave in the circulatory system. Clumping or grouping would hinder their ability to effectively deliver oxygen and could lead to blockages in the microcirculation. Red blood cells are fundamental to the circulatory system, and their traversal through capillaries is vital for normal physiological function.