Emergency Medical Technician Practice Test 2026 – Complete Exam Prep Resource

The main idea is how the vessels differ in direction and oxygen content. In the systemic circuit, arteries carry blood away from the heart and deliver oxygen-rich blood to tissues, while capillaries are the sites where oxygen and nutrients are exchanged for waste products. Veins then return blood toward the heart, and in systemic circulation that blood is usually deoxygenated. The only exception is the pulmonary circulation, where the pulmonary veins carry oxygenated blood from the lungs back to the heart. So saying that veins carry oxygenated blood to all cells misstates their typical role in the systemic circuit. Blood does carry nutrients, and capillaries indeed exchange gases and nutrients, and arteries carry blood away from the heart.