Patient Care Technician (PCT) AAH Practice Exam

Capillaries are best described as:

1. Large blood vessels that carry away from the heart

2. Thick vessels with muscular walls

3. Fine branching blood vessels forming a network

4. Veins that return blood to the heart

The correct answer is: Fine branching blood vessels forming a network

Capillaries are the smallest and most numerous blood vessels in the body, crucial for the exchange of oxygen, nutrients, and waste products between blood and tissues. They are characterized by their thin walls, which consist of a single layer of endothelial cells. This structure facilitates efficient diffusion and permeability, allowing for the transfer of materials at the cellular level. Capillaries form a dense network, connecting arterioles (smaller arteries) to venules (smaller veins), enabling widespread distribution throughout tissues. Other options describe different types of blood vessels. The first option refers to arteries, which carry oxygenated blood away from the heart. The second option describes the characteristics of arteries or veins, as they do possess muscular walls to help regulate blood flow. The last option pertains to veins, which return deoxygenated blood back to the heart. Each of these types of vessels plays a distinct role in the circulatory system, while capillaries uniquely serve as the sites for interchange at the tissue level.