Transport in Humans (part 2): Blood vessels

1. 2) Blood vessels

2. Heart Blood vessels Artery Vein Types of blood vessels arteries • carry blood away from heart veins • return blood to heart capillaries • connect arteries to veins • exchange materials with body tissues Capillary Venule Arteriole

3. Cross-sectional area as it relates to blood pressure and velocity

4. Arteries • carries oxygenated blood (except pulmonary artery and umbilical artery) • blood transport from heart to organs • Thick, muscular, elastic • high pressure • small lumen • no valves

5. Veins • Carries deoxygenated blood • Blood transport from organs to heart • Thin, less muscular • Low pressure • Large lumen • valves within them to prevent backflow of blood

6. Veins

7. Blood flow in veins muscle (contract) muscles beside vein contract action of valves valve flaps pushed apart by blood pressure vein is squeezed by muscles blood flows towards heart valve flaps pushed together by backflow of blood

8. Differences between Artery & Vein Artery • thick & Vein elastic wall • small lumen • thin wall • no valves • large lumen • valves are present

9. Comparison of artery and vein artery vein • thick muscular wall of the artery to the vein • lumen of the vein is slightly larger and commonly holds more blood

10. Artery vs veins:

11. Comparison of arteries and veins

12. Capillary

13. Capillaries •allow exchange of materials between the blood and the body tissues O2 , arterioles capillaries nutrients CO2 , waste venules •the wall is thin & permeable to O2, CO2, glucose, water ... etc. 3-dimensional diagram of capillary

14. Capillary network • Site of exchange of gases, nutrients and wastes • Walls are one cell thick • Great length of capillaries throughout body • Immense surface area for exchange of materials • Exchange between blood in capillary and surrounding tissue/interstitial fluid

15. Exchange of Materials between Capillaries and Tissue Cells • Colourless liquid between minute spaces of tissue cells = tissue fluid • Cells are bathed by the tissue fluid which carries in solution dissolved food substances and O2 • These dissolved substances diffuse into the tissue cells • Waste products diffuse from cells into the tissue fluid and then through the capillary walls into the blood and to the excretory organs for removal

16. Exchange of materials between the blood and the body cells white blood cells capillary water O2 nutrients plasma waste products CO2 tissue fluid cell Diffuse across the capillary Diffuse across the capillary wall Squeeze through the wall wall

17. Capillaries Narrow → RBCs move in a single file through the lumen of capillaries RBCs may become bell-shaped when they pass through the lumen of capillaries Advantages: 1. Diameter of the RBC is decreased (pass through lumen of capillaries easily) 2. Increases s.a. to speed up absorption/ release of O2 3. Rate of blood flow is reduced → increase efficiency of gaseous exchange (more time) • •

18. Formation of the tissue fluid tissue fluid At arterial end : blood pressure pressure of tissue fluid some materials are forced out of the capillaries high pressure tissue fluid arteriole body cell capillary bed red blood cell

19. Formation of the tissue fluid similar to blood plasma but NO plasma proteins and red blood cells Tissue fluid is mainly water with some mineral salts, fats, sugars and hormones too large to be forced through capillary tissue fluid wall capillary bed

20. Formation of the tissue fluid At venous end : blood pressure fluid some tissue fluid return to capillaries , others are drained into lymph vessels pressure of tissue lymph venule capillary bed

21. How does exchange take place?

22. Activity: In your groups, come out with a table stating the characteristics of the artery, vein and capillary Use the following table as a template Template Answer