11.3 Blood Vessels

2026 📋 Syllabus Objectives

By the end of this topic, you should be able to:

  1. Name the main blood vessels that carry blood to and from the heart, lungs, liver, and kidneys — including the aorta, vena cava, pulmonary artery, pulmonary vein, hepatic vein, hepatic artery, hepatic portal vein, renal artery, and renal vein.
  2. Describe and identify the structure of arteries, veins, and capillaries, focusing on: wall thickness, wall composition (muscle and elastic tissue), lumen diameter, and presence of valves.
  3. Explain how the structure of each type of blood vessel is related to the pressure of the blood it carries.

📖 Main Content

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Section 1: Main Blood Vessels of the Body

Your blood does not just flow randomly around your body — it travels through a network of specific blood vessels (tubes that carry blood). Each major organ has dedicated vessels bringing blood to it and carrying blood away from it.

Here is a simple rule to remember:

  • Arteries carry blood away from the heart.
  • Veins carry blood back to the heart.

⚠️ Important exception: The pulmonary artery carries deoxygenated blood (blood without much oxygen), and the pulmonary vein carries oxygenated blood. This is the opposite of what most arteries and veins do — but the naming rule (artery = away from heart, vein = toward heart) still applies.

🫀 Blood Vessels of the Heart

Blood VesselDirection of Blood FlowWhat it Carries
AortaAway from the heart (to the body)Oxygenated blood
Vena CavaToward the heart (from the body)Deoxygenated blood
  • The aorta is the largest artery in the body. It carries oxygenated blood from the left side of the heart out to the rest of the body.
  • The vena cava is the largest vein in the body. It carries deoxygenated blood (blood that has delivered its oxygen to the body's cells) back to the right side of the heart. There are actually two parts: the superior vena cava (from the upper body) and the inferior vena cava (from the lower body) — but for your exam, you just need to know "vena cava."

🫁 Blood Vessels of the Lungs

Blood VesselDirection of Blood FlowWhat it Carries
Pulmonary ArteryAway from the heart (to the lungs)Deoxygenated blood
Pulmonary VeinToward the heart (from the lungs)Oxygenated blood
  • The pulmonary artery carries deoxygenated blood from the right side of the heart to the lungs, where it picks up oxygen.
  • The pulmonary vein carries freshly oxygenated blood from the lungs back to the left side of the heart, ready to be pumped around the body.

💡 Memory tip: "Pulmonary" comes from the Latin word for lung. So pulmonary vessels = lung vessels.

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