American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

Veins primarily carry deoxygenated blood to the heart, which is why this choice is correct. The majority of the body's veins are responsible for collecting blood that has circulated through the body, delivering oxygen to tissues and collecting carbon dioxide and other waste products. This blood then returns to the heart, where it is pumped to the lungs for reoxygenation.

While it's true that veins can carry nutrient-rich blood, as seen in the hepatic portal vein that collects blood from the gastrointestinal organs, this scenario does not represent the general function of veins across the body. Additionally, veins do not transport oxygenated blood away from the heart; that function is performed by arteries. Similarly, veins do not carry oxygen-poor blood from the lungs. Rather, the pulmonary veins are responsible for returning oxygenated blood from the lungs to the heart. Therefore, the correct depiction of vein function is their role in returning deoxygenated blood to the heart.