1. Contents Blood Vessels What blood vessels do Arteries Capillaries Summary quiz Veins

2. Lungs We can get an idea of what they could look like from considering the job they have to do. 3 Let us look at a small section of the circulatory system. There seems to be 3 types of blood vessel present. one one takes blood away from the heart one one takes blood to the heart one one joins the other two together What blood vessels do

3. 1. ARTERIES Blood vessels that take blood away from the heart are known as ARTERIES. 2. VEINS Blood vessels that take blood back to the heart are known as VEINS. aa Remember, arteries (away) inin Remember, veins (into the heart) Three broad types of vessels

4. 3. arteries veins Finally, if arteries take blood away from the heart and veins take blood back to the heart, when does an artery turn into a vein? Well, our third type of blood vessel links the two. We find it present where an artery finishes and a vein is about to begin. CAPILLARY. This third type of blood vessel is known as a CAPILLARY. and in between…

5. Contents Blood Vessels What blood vessels do Arteries Capillaries Veins Summary quiz

6. Artery cross-section small lumen thick muscle and elastic fibres

7. The small size of the lumen means that blood will be under high pressure. The thick fibrous wall strengthens the artery. Arteriole pressure Imagine using a water hose and putting your thumb half over the open end. The water is released under higher pressure and it flows faster.

8. The elastic allows the artery to stretch under pressure whilst the muscle can contract to push the blood along. thick arteriole wall Properties of arteriole walls lumen

9. This stretching of the artery is what allows us to feel a pulse. blood flow As the heart beats, it releases regular surges of blood. As these pass along the arteries, the vessel must stretch to allow the increased blood flow to pass. This stretching pushes on the skin, which we sense as a pulse. blood flow The human pulse

10. The blood flowing through an artery will be under high pressure and moving extremely fast. There is no chance that the blood will turn around and start travelling in the opposite direction. no valves Therefore, there are no valves present in arteries. Blood flow in arteries

11. Contents Blood Vessels What blood vessels do Arteries Capillaries Veins Summary quiz

12. large lumen thin muscle and elastic fibres Veins: cross-section

13. The lumen of a vein is much thicker than the wall that surrounds it. There is less of a need to maintain a high pressure. The walls still contain elastic and muscle but there is far less present compared to the artery. You will appreciate that the blood is flowing far less quickly through veins compared to arteries. Walls of veins

14. The veins are carrying blood back towards the heart. Materials have been exchanged and now it is running out of energy. It needs to return to the heart to receive another pump. Unfortunately, this could lead to a real problem... Getting another boost

15. leg Q. What would happen if blood loses so much energy that it stops and turns around? vein This situation could arise where blood is flowing against gravity. However, there is a solution to this problem and it comes in two parts. Preventing backflow Normal direction of blood flow gravity

16. 1.Firstly, veins have valves which act to stop the blood from going in the wrong direction. (These valves are similar to those found in the heart) valves open blood valves close Valves

17. 2.The second part of the solution has to get the blood flowing again whilst overcoming the problem of a lack of muscle in the lining of the vessel. The solution comes in the form of general body muscles that surround the veins. When these muscles contract to move the body, they also squeeze the veins and push the blood along the vessel. → Muscular massage

18. Contents Blood Vessels What blood vessels do Arteries Capillaries Veins Summary quiz

19. These vessels link arteries with veins. They are found all over the body and are essential for the exchange of materials between the blood and other body cells. arteryvein capillaries Capillaries: role and position

20. very narrow lumen The wall of a capillary is only one cell thick! Capillaries are so small that they can only be seen using a microscope. capillary bed A collection of capillaries is known as a capillary bed. Capillary bed body cell

21. Substances can diffuse across the lining of the capillary. This allows useful substances which are dissolved within the blood to move into surrounding cells whilst cellular waste moves in the opposite direction. 12 3 The exchange of materials between the blood and the body can only occur through capillaries. Diffusion and exchange

22. Exchange of dissolved gases Oxygen and carbon dioxide exchange in the capillaries.

23. Vessel test. Part 1

24. Reaching all parts

25. Vessel test. Part 2

26. Blood characteristics

27. Contents Blood Vessels What blood vessels do Arteries Capillaries Veins Summary quiz

28. Multiple-choice quiz