Overview
This lecture explains the structure and function of different blood vessels—arteries, capillaries, and veins—and introduces how to calculate blood flow rate.
Types of Blood Vessels
- Arteries carry blood away from the heart at high pressure.
- Capillaries exchange nutrients, oxygen, and waste products with body tissues.
- Veins return blood to the heart at low pressure.
Arteries: Structure and Function
- Arteries have thick muscular and elastic walls to withstand high pressure from the heart.
- The wall of the artery is thick compared to the lumen (the inner space).
- Arteries stretch and recoil due to elastic tissue.
Capillaries: Structure and Function
- Capillaries are very small and closely contact all body cells.
- Their walls are one cell thick and permeable for easy diffusion.
- Capillaries have a tiny lumen but collectively a very large cross-sectional area.
- Blood pressure in capillaries is low and flows slowly to allow exchange of substances.
Veins: Structure and Function
- Veins have large lumens and thin walls with small layers of muscle and elastic fibers.
- Blood pressure in veins is very low, so walls do not need to be strong.
- Veins contain valves to prevent backflow and ensure blood flows towards the heart.
Calculating Blood Flow Rate
- Rate of blood flow = Volume of blood / Time taken.
- Example: If 2560 ml flows in 8 minutes, rate = 2560 Ă· 8 = 320 ml/min.
Key Terms & Definitions
- Artery — Vessel carrying blood away from the heart at high pressure.
- Capillary — Tiny vessel for exchanging substances between blood and tissues.
- Vein — Vessel carrying blood back to the heart at low pressure.
- Lumen — The inner open space within a blood vessel.
- Valve — Structure in veins that prevents backward blood flow.
Action Items / Next Steps
- Review blood vessel diagrams and their structural features.
- Practice calculating blood flow rates using provided method.
- Watch related videos on the heart and blood for broader understanding.