1. This section of the system including the right side of the heart, deals with the deoxygenated blood. This section of the system including the left side of the heart, deals with the oxygenated blood. Lungs Body cells Because of this our circulatory system is in two parts. It is in fact called a double circulatory system. A double circulatory system

2. The human circulatory system

3. The heart is made almost entirely of muscle. It is unlike any other muscle in your body because it never tires. And even though it is full of blood it still needs it own blood supply. Oxygenated blood is carried to the heart by the coronary arteries. Each side of the heart has two chambers. 1. An top chamber or atrium and 2. A bottom chamber or ventricle Each of these chambers has its own function. Look at the diagram on the next slide to see what that is. One big muscle

4. Diagrammatical representation

5. Besides the chambers there is also another very important part of the heart – the valves. These valves are found between the top and bottom chambers on both sides of the heart. blood valve These valves are rather like doors that only open in one direction. The valves: structure and function

6. As the atrium fills with blood, the valves are closed. When the atrium contracts and squeeze the blood, the valves are pushed open. These valves are connected to the side wall of the heart by tough tendons. These tendons allow the valves to close but not invert. Valves in action

7. valve tendon wall of ventricle These tendons can be compared to an arm holding onto the handle of a door. Tendon holding a valve

8. we also find valves here...and here! These extra valves stop the blood from re-entering the heart when it is pumped from the ventricles. More valves

9. When the blood knocks against the second set of heart valves, it makes a ‘dub’ like sound. valve ventricle artery The blood ‘slaps’ against the valve and then passes along the artery. These two sounds – lub and dub – are actually what we hear as our heartbeat. So our heartbeat is in fact the sound of the valves opening and closing. When the blood knocks against the first heart valves, it makes a ‘lub’ like sound. Lub - dub

10. Now that we can name all of the parts of the heart it is time to see how they work to push blood around the body. The heart pumps blood when its muscle contracts. As the muscle contracts the chamber gets smaller and squeeze the blood out. The two sides of the heart work together. The atria contract and relax at the same time, as do the ventricles. The next two slides describe what occurs inside the heart during one heart cycle. The action in motion

11. blood from the body blood from the lungs 1. The heart beat begins when the heart muscles relax and blood flows into the atria. 2.The atria then contract and the valves open to allow blood into the ventricles. The action in motion

12. The staged cycle then repeats itself. 3.The ventricles contract forcing the blood to leave the heart. At the same time, the atria are relaxing and once again filling with blood. The action in motion

13. This journey is far less demanding. The right ventricle only has to pump blood from the heart to the adjacent lungs. This journey is enormous. The left ventricle has to pump blood all over the body! Therefore, the left ventricle needs a thicker wall to generate a stronger ‘squeeze’ on the blood. body cells lungs Different destinations

14. Drag the labels to the correct numbered boxes on the diagram of the blood system.

15. Label the heart

16. Answer the questions

17. Multiple-choice quiz