Overview
This lecture explains the differences between arteries and veins, clarifies common misconceptions, and outlines their roles in the circulatory system.
Arteries vs. Veins: Basic Concepts
- Arteries and veins are blood vessels with different roles in blood circulation.
- A common misconception is that arteries always carry oxygenated blood and veins always carry deoxygenated blood; this is not always true.
- Blood in veins is not actually blue; it appears blue through the skin due to light absorption and reflection.
Proper Definitions and Blood Flow
- Arteries carry blood away from the heart, regardless of blood oxygen content.
- Veins carry blood toward the heart, regardless of blood oxygen content.
- Capillaries are small vessels where gas and nutrient exchange occur; they connect arteries and veins.
- Pulmonary arteries carry deoxygenated blood from the heart to the lungs.
- Pulmonary veins carry oxygenated blood from the lungs back to the heart.
- Systemic circulation moves blood between the heart and the rest of the body.
- Pulmonary circulation moves blood between the heart and the lungs.
Pressure, Volume, and Structure
- Arteries have high pressure because blood is pumped directly by the heart.
- Veins operate under lower pressure and often contain valves to prevent backflow.
- Most blood volume (about 65%) is in veins, while only around 15% is in arteries.
- Capillaries and the heart contain about 5% and 5% of blood volume, respectively, while the lungs hold about 10%.
Key Terms & Definitions
- Artery — blood vessel that carries blood away from the heart.
- Vein — blood vessel that carries blood toward the heart.
- Capillary — tiny blood vessels where gas and nutrient exchange occurs between blood and tissues.
- Pulmonary artery — artery carrying deoxygenated blood from the heart to the lungs.
- Pulmonary vein — vein carrying oxygenated blood from the lungs to the heart.
- Systemic circulation — movement of blood between the heart and the body (excluding the lungs).
- Pulmonary circulation — movement of blood between the heart and the lungs.
Action Items / Next Steps
- Review the definitions and differences between arteries and veins.
- Memorize the pathway of blood flow through the heart, lungs, and body.
- Study diagrams showing systemic and pulmonary circulation.