Veins

Definition

Veins are blood vessels that carry blood toward the heart. They typically transport deoxygenated blood from the tissues back to the heart, except for the pulmonary veins which carry oxygenated blood.

5 Must Know Facts For Your Next Test

1. Veins have valves that prevent backflow of blood and ensure it flows in one direction toward the heart.
2. Veins are part of the low-pressure system within the circulatory system compared to arteries.
3. The largest vein in the body is the inferior vena cava, which carries blood from the lower body to the heart.
4. Venous walls are thinner and less muscular than arterial walls due to lower pressure requirements.
5. Varicose veins occur when vein valves malfunction, causing blood to pool and veins to enlarge.

Review Questions

• What structural feature do veins possess that prevents backflow of blood?
• How does the pressure in veins compare to that in arteries?
• Which major vein carries deoxygenated blood from the lower body to the heart?

Related terms

Arteries:

Blood vessels that carry oxygen-rich blood away from the heart under high pressure

Capillaries:

Tiny blood vessels where gas exchange occurs between blood and tissues

Pulmonary Veins: Veins that carry oxygenated blood from the lungs to the left atrium of the heart