Transport in Humans (part 3): The structure and function of the human heart

1. 3) Heart

2. Lesson Objectives: • Double & single circulation • Structure of heart • Mode of action of heart

3. Double circulation in mammals Blood vessels Circulatory system Heart Blood The mammalian circulation plan Lung pulmonary circulation As blood passes through heart twice, this also known as double circulation systemic circulation All other parts of the body

4. The pulmonary circulation 3 The blood becomes oxygenated 1 Deoxygenated blood in right ventricle 2 The blood is pumped through pulmonary artery into lungs for gas exchange 4 The blood flows through pulmonary veins to left atrium The human circulatory system

5. The systemic circulation 3 O2and nutrients diffuse into cells while CO2 and wastes diffuse out 1 Oxygenated blood in left ventricle 2 The blood is pumped through aorta to all parts of the body except lungs 4 The blood flows through inferior/ superior vena cava to right atrium The human circulatory system

6. Single circulation Systemic circulation

7. Heart Click me!

8. External Structure of heart Heart consists of 4 chambers 2 atria (right atrium and left atrium) – smaller – on the upper part 2 ventricles – larger – below atria (plural) right atrium left atrium left ventricle right ventricle

9. Internal Structure of heart Heart consists of 4 chambers 2 atriums – smaller – on the upper part 2 ventricles – larger – below atriums right atrium left atrium left ventricle right ventricle

10. Atriums and ventricles are separated by valves to prevent backflow of blood semi-lunar valves tricuspid valve bicuspid valve Septum chordae tendineae holds valves in position and avoids them to turn inside-out prevents mixing of blood in both sides of the heart

11. Blood flow and blood vessels pulmonary artery to lung aorta from body to body from lung superior vena cava pulmonary veins inferior vena cava from body deoxygenated blood oxygenated blood

12. Circulation of blood around the body Arterial supply Venous return

13. External Structure of heart pulmonary vein aorta pulmonary artery coronary artery superior vena cava coronary vein inferior vena cava

14. Structure of heart Superior vena cava chordae tendineae aorta Pulmonary artery Right atrium Pulmonary valve Pulmonary vein Left atrium bicuspid valve tricuspid valve Left ventricle Inferior vena cava Right ventricle aortic valve Median septum

15. Activity: Label the following diagram of the heart in the worksheet provided

17. Names of important arteries & veins

18. quiz…

19. Label the external parts of the heart: 1. superior vena cava 2. aorta 3. pulmonary arteries 4. left atrium 5. right atrium 6. right ventricle 7. left ventricle 8. right coronary vein 9. right coronary artery 10. apex

20. Label the internal parts of the heart: 1. superior vena cava 2. right atrium 3. tricuspid valve 4. right ventricle 5. papillary muscle 6. aorta 7. pulmonary artery 8. left atrium 9. bicuspid valve 10. median septum

21. Mode of action of heart

22. Mode of action right atrium left atrium Backflow prevented by tricuspid valve Backflow prevented by bicuspid valve contract simultaneously right ventricle left ventricle contract simultaneously aortic arch pulmonary arch (atria relaxes) (atria contracts)

23. Mode of action • closing of tricuspid & bicuspid ‘ valves produce loud ‘lub’ sound (ventricular contraction/systole) • closure of semilunar valves produce ’dub’ sound (ventricular relaxation/diastole) • one systole + one diastole = one heartbeat • atria and ventricle work alternately

24. Blood pressure

25. Blood pressure • Force of blood exerted on blood vessel walls • Highest during ventricular systole, when blood is forced into arteries • Decreases during ventricular diastole • Varies in different parts of the body (arteries near heart → high; veins (far from heart → low) • Varies with individuals Normal person: systolic pressure = 120-140mm of mercury diastolic pressure = 75-90mm of mercury • Blood pressure is given as the systolic pressure being the first number than diastolic pressure being the second number e.g. 120/80 (120 over 80) • High blood pressure when blood pressure is 140/90 or higher

26. High blood pressure • High blood pressure when blood pressure is 140/90 or higher • May occur temporarily after heavy exercise or when a person is angry • Persistent high blood pressure (in middle- aged or elderly people) is a dangerous medical condition • Can be easily controlled if they see a doctor in time and follow the medical advice given

27. ***Pressure changes in the heart (Refer to pg 161 Biology Textbook) Recall • one systole + one diastole = one heartbeat • atria and ventricle work alternately (ventricular systole + atrial diastole occur simultaneously and atrial systole + ventricular diastole occur simultaneously)

28. Increase in pressure due to blood flowing into the aorta when the ventricle contracts Pressure in the aorta rises due to backflow of blood in the aorta Pressure in the aorta follows that of the pressure in the ventricle (pressure is slightly lower) Increase in pressure due to blood flowing into the ventricle when the atrium contracts

29. For bicuspid valve to open, pressure in the left atrium must be high and vice versa ( D ) ‘O’ Level Bio P1 Nov 2008

30. Atrio-ventricular valve = bicuspid or tricupid valves Semi-lunar valve = valve in aorta Between W and X, ventricular pressure is increasing hence atrio ventricular valves would be closed and semi lunar valve would open as blood is pushed through the aorta ( B ) ‘O’ Level Bio P1 Nov 2006

31. 0.6 s = one heartbeat 60/0.6 = 100 heartbeats per min ( C ) ‘O’ Level Bio P1 Nov 2006

32. Pulse

33. Pulse (produced after every ventricular contraction) ventricular contraction blood is pumped into aortic arch blood is pumped into arteries increased pressure causes arteries dilate walls of arteries recoil Blood forced along in series of waves [Imagine a fireman’s hose]

34. Experiment to demonstrate the presence of valves in veins

35. Demonstrating the presence of valves Procedure: • Bandage the upper arm (valves in veins appear as small swellings) [see above] • Place 2 fingers at point Y • Using one finger push blood to point X • Blood flowed back to from X to b and no further

36. Heart diseases

37. Coronary Heart Disease

38. Coronary Heart Disease • Coronary arteries lie on the outside of the heart and carry blood to the muscles in the walls of the heart • Blood supply to the heart can be greatly reduced if the coronary arteries become blocked or narrowed 1) Angina (chest pains) Narrowing/ blocking of coronary arteries 2) Heart attack

39. Transverse sections of 2 arteries (cholesterol + polysaturated fats)

40. 1) Angina

41. 2) Heart Attack!!! Fatty substances (cholesterol and polysaturated fats) may be deposited on the inner surfaces of the coronary arteries (atherosclerosis); This narrows the lumen of these arteries + increases blood pressure; Such an affected artery develops rough inner surfaces, which increases the risk of a blood clot being trapped in the artery (thrombosis); If it occurs in the coronary arteries, the supply of blood and oxygen to the heart muscles may be completely cut off. The heart muscle cells may be damaged and die, triggering a heart attack. • • • •

42. Atherosclerosis

43. Atheroma formation A thrombus is an aggregate of a network of fibrin, platelets, and blood elements trapped by the fibrin net

44. Factors that increase the risk of atherosclerosis and coronary heart disease 1. A diet rich in cholesterol and saturated animal fats 2. Emotional stress 3. Smoking

45. Preventive measures against coronary heart disease • Proper diet – rich in dietary fibres; substitute animal fats with polyunsaturated plant fats • Proper stress management • Avoid smoking - Nicotine increases blood pressure - CO increases risk of fatty deposits on inner surfaces of arteries • Regular physical exercise - strengthens the heart and maintains elasticity of arterial walls

47. Ballooning & Stent Insertion