Veins

Definition

Veins are blood vessels that carry deoxygenated blood back to the heart. They have thinner walls compared to arteries and often contain valves to prevent backflow of blood.

5 Must Know Facts For Your Next Test

1. Veins work against gravity, especially in the legs, requiring valves to prevent backward flow.
2. The largest vein in the human body is the inferior vena cava.
3. Unlike arteries, veins have lower pressure and rely on skeletal muscle contractions to move blood.
4. Pulmonary veins are an exception as they carry oxygenated blood from the lungs to the heart.
5. Vein walls are composed of three layers: tunica intima, tunica media, and tunica externa.

Review Questions

• What function do valves in veins serve?
• How do veins differ from arteries in terms of structure and function?
• Which vein carries oxygenated blood from the lungs to the heart?

Related terms

Arteries:

Blood vessels that carry oxygenated blood away from the heart under high pressure.

Capillaries: Tiny blood vessels where exchange of gases, nutrients, and waste occurs between blood and tissues.

Inferior Vena Cava: The large vein that carries deoxygenated blood from the lower body back to the heart.