Question

the circulatory system works as follows, arteries carry oxygenated blood from the heart to a capillary bed, then veins bring it back to the heart.  Discuss where and why exceptions to this occur.

Answer 1

Answer

• The vessels that carry blood away from the heart are called arteries.
• The vessels that carry blood towards the heart are called veins.
• Mostly arteries carry oxygenated blood to body tissues and the veins carry deoxygenated blood back to the heart.
• But there are two exceptions to this :
  
  1) Pulmonary artery
  - Right side of the side pumps deoxygenated blood.
  - Pulmonary trunk (major artery) and its branches transport deoxygenated blood from right ventricle to the lungs (pulmonary capillaries).
  - Hence, pulmonary arteries are the only arteries body that carry deoxygenated blood.

2) Pulmonary veins
- After gaseous exchange (external respiration) between alveoli and pulmonary capillaries, the blood gets oxygenated.
- Pulmonary veins carry this oxygenated blood back to the heart into left atrium.
- Hence, pulmonary veins are the only veins body that carry oxygenated blood.