Electrolysis Practice Exam 2026 - Free Electrolysis Practice Questions and Study Guide

Capillaries are indeed the smallest type of blood vessel in the circulatory system. Their primary function is to facilitate the exchange of oxygen, carbon dioxide, nutrients, and waste products between the blood and tissues. Capillaries are uniquely structured with thin walls, typically only one cell thick, allowing for efficient diffusion of substances. This small size and thinness enable them to reach nearly every cell in the body, providing them with the necessary materials for cellular function and removing waste.

In contrast, veins, arteries, and venules are larger blood vessels. Arteries carry blood away from the heart and have thicker walls to handle high-pressure blood flow, while veins return blood to the heart and typically have valves to prevent backflow. Venules are small vessels that collect blood from capillaries and converge into veins.