Arteries, Arterioles, Veins, Venules , & Capillaries

1. Arteries, Arterioles, Veins, Venules, & Capillaries

2. Arteries • Large hose-like vessels • Carry blood away from the heart. • Have thick, multi-layered muscular walls. • Walls are capable of stretching to accommodate the “pulse” of blood when the heart beats.

3. Arteries • Capable of expanding and contracting to change and maintain the blood pressure. • NO valves • Blood spurts • Blood inside them is high in oxygen & low in carbon dioxide except in pulmonary artery.

4. Arteries • Blood inside is bright red (except pulmonary artery) • Blood inside is under High pressure • Examples: Coronary (heart), Brachial (arms), Carotid (head), Femoral (legs), Renal (kidney).

5. Arterioles • Tiny branches from arteries. • Cannot be seen with unaided eye - microscopic • Thinner, less muscular walls (compared to arteries) • Feed blood into the capillaries • Narrower than arteries, but wider than capillaries

6. Capillaries • Flow and pressure of blood is controlled by sphincters that are outside of the capillaries. • Microscopic vessels ~ 8 µm in diameter. • Erythrocytes (rbc’s) pass through in single file. • Walls are only one cell thick (to facilitate diffusion of materials/exchange).

7. Capillaries • Thinness allows for easy diffusion outward or inward through the single cell layer. • Form capillary beds - networks of vessels linking arterial and venous blood.

8. Capillaries • Oxygen , nutrients and other materials move out of the capillaries and into the extra-cellular fluid and then into cells. • Carbon dioxide, wastes and other materials are picked up and move into the capillaries. • Diffusion enables the movement of substances into and out of capillaries.

9. Venules • Vessels larger than capillaries but smaller (i.e. narrower and thinner walls) than veins. • Collect blood from capillaries.

10. Veins • Larger inside diameter compared to arteries • Take blood towards the heart • Thinner, less muscular walls than arteries, but still 3 layers • No stretching or contracting of walls except by external muscles. • Contain valves to help return the blood to the heart (compensate for lower venous pressure, less muscle in walls, and large diameter).

11. Veins - Valves

12. Veins Blood: • Moves smoothly. • Low in oxygenexcept pulmonary circulation. • Dull red. • Low pressure. • Examples: cardiac (heart), brachial (arms), jugular (head), femoral (legs), renal (kidney).

13. Varicose Veins • When the valves don’t function properly, blood leaks backwards and pools in veins • Veins sag, stretch and swell, creating bulging gnarled vessels

14. The circulatory system of arteries, veins and capillaries