Topic 9.7

1. Topic 9.7 The Circulatory System

2. Contents The Heart and Circulatory System The circulatory system Structure of the heart Valves in the heart How the heart pumps blood

3. How do substances move around the body? The body has its own transport system that carries substances around the body. Which organs are involved in this system? heart blood vessels blood The body’s transport system is called the circulatory system. Why is it given this name?

4. What is carried by the circulatory system? Which gases are transported to and from the body’s cells by the blood flowing in the circulatory system? carbon dioxide oxygen Oxygen is the gas needed for respiration and is transported tothe body’s cells. Carbon dioxide is the waste gas produced by respiration that must be carried away from the body’s cells.

5. Two types of blood c oxygen-rich blood oxygen-poor blood The circulatory system carries two types of blood: • blood travelling to the body cells • high oxygen content • low carbon dioxide content • blood travelling • away from the body cells • low oxygen content • high carbon dioxide content The arrangement of the circulatory system means that these two types of blood do not mix. Why is this important?

6. At the heart of the circulatory system The heart is the organ at the centre of the circulatory system. It pumps blood around the body. How are the two types of blood (oxygen-rich and oxygen-poor) kept apart inside the heart?

7. Inside the heart right side of the heart left side of the heart oxygen-poor blood oxygen-rich blood The inside of the heart is divided into two sections so that the two types of blood (oxygen-rich and oxygen-poor) are kept apart. Remember that the heart is always labelled as if it is in a body facing you, so the right side of the heart is on the left of the diagram.

8. The two sides of the heart

9. How does blood circulate around the body? Blood is pumped around the body by the heart. It takes about 30 seconds for blood to go once around the body. Starting with the left side of the heart, what route does the blood follow to complete one circuit of the body?

10. How does blood circulate around the body? body’s cells body’s cells The left side of the heart pumps oxygen-rich blood to the rest of the body. This blood supplies the body’s cells with oxygen. What gas does the blood pick up from the body’s cells and where does the blood go next?

11. How does blood circulate around the body? body’s cells body’s cells Blood picks up carbon dioxide from the body’s cells. This oxygen-poor blood then travels back to the right side of the heart. The oxygen-poor blood needs to lose the carbon dioxide and pick up more oxygen. How does it do this?

12. How does blood circulate around the body? lungs lungs body’s cells body’s cells Next, the right side of the heart pumps oxygen-poor blood to the lungs. In the lungs the blood gets rid of the waste carbon dioxide and collects more oxygen. Where does this oxygen-rich blood then travel to?

13. How does blood circulate around the body? body’s cells body’s cells The oxygen-rich blood then returns to the left side of the heart. This completes the blood’s journey around the body. Why is the journey of blood through the circulatory system called a double circulation? lungs lungs

14. A double circulatory system body’s cells body’s cells During one complete circuit of the body, blood passes through the heart twice. The heart has two jobs to do and so the circulatory system involves a double circulation. What are the two jobs that the heart carries out during this double circulation? lungs lungs

15. Which way does blood flow?

16. Contents The Heart and Circulatory System The circulatory system Structure of the heart Valves in the heart How the heart pumps blood Summary quiz

17. The structure of the heart – exterior muscle tissue The heart pumps blood around the circulatory system. What is the heart made of? The heart is made of muscle and keeps pumping blood around your body, even when you are asleep! What do the blood vessels on the outside of the heart do?

18. The heart needs blood too! blood vessels supply blood to muscle tissue The heart is full of blood but also needs its own blood supply so that the muscle can keep pumping. muscle tissue The blood vessels on the outside of the heart carry oxygen-rich blood to the heart muscle cells. Oxygen-poor blood is then carried away from these cells by outer blood vessels and back into the heart.

19. The structure of the heart – interior The inside of the heart is divided into two sections to keep oxygen-rich and oxygen-poor blood separate. Each side of the heart is also divided into two sections. right side of the heart left side of the heart Each section of the heart is called a chamber. How many chambers are there? 4

20. The chambers of the heart right atrium left atrium left ventricle right ventricle The four chambers of the heart have special names: An upper chamber is called an atrium (plural atria). A lower chamber is called a ventricle.

21. What do atria and ventricles do? blood to the lungs blood to the body blood from the body blood from the lungs The chambers of the heart have different functions. The atria collect blood that enters the heart. The ventricles pump blood out of the heart.

22. Inside the heart – labels

23. Inside the heart – labelling activity

24. Chambers of the heart – activity

25. Contents The Heart and Circulatory System The circulatory system Structure of the heart Valves in the heart How the heart pumps blood Summary quiz

26. Preventing backflow Blood always flows in the same direction as it moves through the heart during each circulation of the body. Why is it important that blood does not flow backwards?

27. Heart valves valve leading out of left ventricle valve leading out of right ventricle valve between left atrium and left ventricle valve between right atrium and right ventricle The chambers of the heart are separated by valves which prevent blood from flowing in the wrong direction. There are valves between the atria and the ventricles… …and there are valves leading out of the ventricles.

28. Naming the heart valves

29. How are valves held in place? The valves between the atria and ventricles are connected to the inner walls of the heart by tough tendons. valve open

30. How are valves held in place? The tendons allow the valves to close and hold the valve flaps in place. They prevent the valves from flipping up and turning inside out. Why is this important? valve closed valve open

31. How do valves work? A valve acts like a door that only opens in one direction. If the door is held by someone at a fixed point, only the arm moves as the door opens and closes. When the door is closed the arm is fully extended, so the door can onlybe opened in one direction.

32. How do valves work? A valve acts like a door that only opens in one direction. In the heart, the tendons holding the valve are like the arm holding the door. One end of each tendon is fixed to the wall of the heart and so the valve can only open in one direction.

33. Contents The Heart and Circulatory System The circulatory system Structure of the heart Valves in the heart How the heart pumps blood

34. How does the heart pump blood? Imagine the force needed to squeeze a tennis ball. That’s how much force the heart uses to pump blood around the body! How does the heart produce enough force to keep doing this 24 hours a day? The heart can pump blood because it is made of muscle. Muscle tissue works by contracting (squeezing) and relaxing.

35. How does the heart pump blood? All the parts of the heart on either side, work together in a repeated sequence. The two atria contract and relax; then the two ventricles contract and relax. This is how blood moves through the heart and is pumped to the lungs and the body. One complete sequence of contraction and relaxation is called a heartbeat.

36. Heartbeat animation

37. Stages of a heartbeat Stage 1: A heartbeat begins with the heart muscle relaxed and valves closed. Blood flows into the two atria and both sides fill up with blood. This blood has to be pushed through the valves to get into the ventricles. How does this happen?

38. Stages of a heartbeat Stage 2: The atria contract and the blood is squeezed which causes the valves leading to the ventricles to open. Blood then flows from the atria into the ventricles. What happens to the open valves when the atria are empty?

39. Stages of a heartbeat Stage 2 (continued): The valves between the atria and the ventricles close. This prevents any backflow. What happens next to the blood in the ventricles?

40. Stages of a heartbeat Stage 3: Almost immediately, the ventricles contractand the blood is squeezed again. The pressure of the blood forces open the valves leading out of the heart. Blood is pumped out of the heart. What happens to the open valves when the ventricles are empty?

41. Stages of a heartbeat Stage 3 (continued): When the ventricles are empty, the valves leading out of the heart close and the heart muscle relaxes. This completes the sequence of contraction and relaxation in one heartbeat. What will happen next?

42. Stages of a heartbeat Stage 1 (again): The atria fill up with blood as the heartbeat sequence begins again. Why are the walls of the atria thinner than the walls of the ventricles? Why is the wall of the left ventricle thicker than the right ventricle?

43. Listening to a beating heart: lub-dub What does a doctor hear when they listen to a patients’ heart? lub-dub, lub-dub, lub-dub, lub-dub, lub-dub, lub-dub… The sound of a heartbeat is the sound of the heart valves. The “lub” is caused by the closing of the valves leading to the ventricles. The “dub” is caused by the closing of the valves leading out of the heart.

44. Measuring a beating heart You can measure how fast your heart is beating by taking your pulse. Place the fingertips of one hand on the opposite wrist, where an artery passes near the surface of the skin. Each pulse that you feel is due to the pressure of blood leaving the heart as the left ventricle contracts. What is your heartrate, in beats per minute, right now?

45. How many heartbeats? If your heart beats at an average rate of 70 times per minute, how many heartbeats are there… …in one hour? …in one day? …in one year? …in 70 years? 4,200 70 x 60 = 100,800 4,200 x 24 = 36,792,000 100,800 x 365 = 2,575,440,000 36,792,000 x 70 =

46. The sequence of a heartbeat

47. Journey of blood around the body

49. Flow of Blood Superior and Inferior vena cava  right atrium  tricuspid valve  right ventricle  pulmonary valve  pulmonary artery  lungs (exchange of gases O2 & CO2)  pulmonary vein  left atrium  mitral valve  left ventricle  aortic valve  aorta  arteries  body systems SUMMARY:

50. Types of Blood Circulation Pulmonary Circulation – blood flows from the heart to the lungs to get O2 supply. Systemic Circulation – blood flows from the heart to the cells (distribute food and O2) and from the cells to the heart (carry wastes and to the heart CO2)