Blood Vessels
What Are Blood Vessels?
Blood vessels are tubes that carry blood around the body. They are a key part of the circulatory system, linking the heart with organs and tissues.
💡 Key Concept: There are three main types of blood vessels: arteries, veins, and capillaries, each with different structures and functions.
Types of Blood Vessels
| Vessel | Function | Key Features |
|---|---|---|
| Arteries | Carry blood away from the heart | Thick, elastic walls; small lumen; high pressure |
| Veins | Carry blood towards the heart | Thinner walls; large lumen; valves to prevent backflow |
| Capillaries | Exchange of substances with tissues | Very thin walls (1 cell thick); tiny lumen; low pressure |
Arteries
✔ Carry oxygenated blood (except pulmonary artery)
✔ Have thick, muscular, and elastic walls to cope with high pressure
✔ Narrow lumen to maintain pressure
✔ Pulse can be felt in arteries like the wrist or neck
Veins
✔ Carry deoxygenated blood (except pulmonary vein)
✔ Have thinner walls and larger lumen
✔ Contain valves to stop blood flowing backwards
✔ Blood flows at low pressure, helped by muscle contractions
Capillaries
✔ Found in tissues and organs
✔ Allow exchange of oxygen, glucose, and waste products
✔ Walls are one cell thick – short diffusion distance
✔ Very narrow – increases surface area for exchange
Questions
- How many chambers does the heart have?
- What does the pulmonary artery do?
- Why does the left ventricle have a thicker wall?
- What do valves in the heart do?
- Which blood vessel brings oxygenated blood back from the lungs?
Summary
- The heart pumps blood in a double circulatory system – to the lungs and body.
- It has four chambers and is connected to major blood vessels.
- Valves ensure blood flows in one direction.
- The left side pumps oxygenated blood; the right side handles deoxygenated blood.