1. Human Circulatory System
Heart and Blood Vessels

2. Contents
In single celled organisms In small multicellular organisms Circulatory system Types of Circulatory System The Human Circulatory System Blood vessels Exchange of materials Portal blood system The Heart Valves in heart
Systole & Diastole Heartbeat Blood Pressure Healthy Circulatory System The Lymphatic System Blood and Lymph vessels – diagram Lymph System Composition The Lymph System Lymph nodes Functions of the Lymph System

3. In single celled organisms
All cells need to take in various nutrients e.g. oxygen
All cells need to get rid of waste products e.g. carbon dioxide
Single celled organisms e.g. Amoeba, achieve this by diffusion

4. Exchange of materials in Amoeba

5. In small multicellular organisms
Small multicellular organisms e.g. flatworms have bodies only a few cells thick
They too can exchange materials with their environment by diffusion

6. Exchange of materials in a flatworm

7. Circulatory system
Larger multicellular animals need a circulatory system
as the distance from the body surface to the centre is too great for diffusion
A circulatory system consists of: -
A fluid called blood
A pump called a heart
Tubes or vessels to carry the blood to the cells of the body

8. Types of Circulatory System
Two types
Open Circulatory System
Closed Circulatory System

9. Open Circulatory System
Blood not always found in blood vessels
Heart pumps blood into open ended vessels and into body cavity
Body cells bathed in blood – exchange of materials takes place
Blood passes back into blood vessels and back to heart
This type of circulatory system is found in insects

10. Open circulatory system
Go to Slide 58

11. Closed Circulatory System
Blood remains in blood vessels
Exchange of materials possible – smallest blood vessels have thin walls
Materials diffuse from the blood into the tissue fluid and then into the body cells
All cells are surrounded or bathed in a fluid called tissue fluid (E.C.F.) – a medium for the exchange of materials
Found in earthworms and vertebrates – a more efficient system

12. Closed Circulatory System

13. The Human Circulatory System
Humans have a double circulatory system i.e. blood is pumped from the heart to the lungs and back to the heart This is pulmonary circulation and from the heart to the body and back to the heart This is systemic circulation

14. Double circulation in humans

15. Separate systems
Heart divided by a muscular wall into left and right sides
Right side pumps deoxygenated blood to the lungs (pulmonary)
Left side pumps oxygenated blood to the body (systemic)
Advantage of double circulatory system is adequate blood pressure ensured for both systems.

16. Blood vessels
Three types
Arteries
Veins
Capillaries

17. Arteries Thick-walled Small lumen (central cavity)
Carry blood away from the heart
Blood under pressure from heart

18. T.S. Artery and Vein

19. Veins Thinner walls than arteries Larger lumen Have valves – for what?
Carry blood to the heart
Less pressure – not under influence of heart
Contraction of body muscles squeeze veins and push blood back to heart

20. Branching network Arteries branch into smaller arterioles
Arterioles branch into capillaries

21. Capillaries Are the smallest blood vessels
Are thin-walled – one cell thick
Lie close to nearly every cell in the body – ensuring efficient exchange of material
Allow exchange of substances between blood and body cells
Reunite to form venules and veins which returns blood to the heart

22. Exchange of materials

23. The structure of the blood vessels

24. Differences between arteries, veins & capillaries
Artery
Vein
Capillary
Structure
Function
Blood flow
Thick, three-layered wall of muscle & elastin
Thin, three-layered wall of muscle & elastin
Wall only one cell thick
Extremely narrow lumen
Narrow lumen
Large lumen
No valves
Valves present
No valves
Carry blood away from heart
Carry blood to heart
Allows exchange of materials between …
Rapid under pressure from heart
Sluggish under low pressure
Pressure reducing
Blood flows in pulses
Blood flows steadily

25. Portal blood system (1/3)
The pulmonary and systemic circulatory systems begin and end in the heart. Pulmonary System (refer to a diagram) Heart  Pulmonary Artery  Arterioles  Capillaries in lungs  Venules  Pulmonary Vein  Heart

26. Portal blood system (2/3)
Systemic System Heart  Aorta  Arterioles  Capillaries in body organs  Venules  Veins  Heart The Portal System begins and ends in capillaries e.g. hepatic portal system Capillaries (in stomach & intestines)  Venules  Hepatic Portal Vein  Venules  Capillaries (in the liver)

27. Portal blood system (3/3)
Usually blood flows Artery  capillary  vein The portal system is an exception to this

28. The human circulatory system showing the portal system

29. The Heart Hollow muscular organ Slightly to the left of the sternum
Above the diaphragm
Size of clenched fist – 300g

30. Cardiac muscle
Surrounded by fluid filled chamber (friction free movement) and protective sac = pericardium
Heart wall made of cardiac muscle
Contracts without nervous stimulation
Will not fatigue

31. Cardiac Blood Supply Consists of the coronary blood vessels i.e.
Coronary arteries bringing nutrients to the cardiac tissue from the aorta, and
Coronary veins carry deoxygenated blood back to the right atrium
Emerging from the heart are the aorta, vena cava, pulmonary arteries and veins.

32. External view of human heart

33. Internal structure of heart
Four chambers – 2 upper & 2 lower
Two upper atria – thin walled
Two lower ventricles – thick walled and larger than atria
Divided vertically into left and right by wall – septum
Blood does not flow through the septum

34. Diagram of internal heart structure

35. Questions Describe the direction of blood flow through the heart.
Why is the wall of the left ventricle thicker than that of the right ventricle?
Why are atrial walls thinner than ventricle walls?

36. Valves in heart
Found at the exits of each chamber Four chambers  four valves Function: to prevent a back flow of blood

37. Operation of valves in the heart

38. How to draw the heart (1/6)

39. How to draw the heart (2/6)

40. How to draw the heart (3/6)

41. How to draw the heart (4/6)

42. How to draw the heart (5/6)

43. How to draw the heart (6/6)

44. Systole & Diastole
systole: contraction phase of cardiac cycle during which the chambers discharge the blood. diastole: relaxation phase of cardiac cycle during which the chambers fill with blood.

45. Heartbeat (1/2)
Pacemaker (S-A node) located in right atrium sends out wave of impulses to muscles of both atria causing atria to contract. This is Atrial systole. The impulses are picked up by the atrio-ventricular node (A-V node)

46. Heartbeat (2/2)
and transmitted to the ventricles via the Purkinje fibres - causing the ventricles to contract. This is Ventricular systole. While the atria are contracting and emptying (atrial systole) the ventricles are relaxing and filling with blood (ventricular diastole) and vice versa

47. Heartbeat – diagram

48. Heartbeat sound
The lupp-dup sound, heard through a stethoscope, is caused by the closing of the valves of the heart

49. The Pulse
When the ventricles contract blood is forced through the aorta and into the arteries. This causes the arterial walls to expand and contract rhythmically. This is the pulse and can be felt where an artery is near the body surface e.g. wrist, temple, neck.

50. Blood Pressure
Is caused by the pumping action of the heart. Needs to be reasonable high to keep the blood moving. Highest pressure is where the blood is forced into the aorta by contraction of the left ventricle = systolic pressure Lowest pressure is when the ventricles relax = diastolic pressure

51. Taking blood pressure
Use a B.P. machine = sphygmomanometer Measures pressure required to stop the blood flow in artery of upper arm Contraction and relaxation pressures recorded Expressed as a fraction Systolic pressure Diastolic pressure

52. Blood pressure readings
e.g. healthy young adults B.P. = 110/75 mmHg Hypertension = abnormally high blood pressure i.e. > 140/90 mmHg Hypotension = abnormally low blood pressure.

53. Healthy Circulatory System
Effects of Exercise, Diet and Smoking on the circulatory system

54. Exercise
When we exercise the heart beats faster. Makes the heart muscle stronger and more efficient at pumping blood Improves the oxygen supply to the cardiac muscle and Reduces blood pressure

55. Diet
Too much cholesterol from animal fats can build up on the inner walls of the arteries and reduces the rate of flow of the blood e.g. a blockage in the cardiac artery prevents blood and oxygen getting to the cardiac muscle and will cause a heart attack Eating fewer fatty meats and fatty dairy products can reduce the risk of heart disease

56. Smoking
Major cause of heart disease Tobacco smoke contains nicotine and carbon monoxide (CO) Nicotine increases blood pressure CO interferes with the transport of oxygen to the body cells High levels cause hardening of the arteries

57. The Lymphatic System

58. The lymphatic system
Forms part of the transport system and the immune system Collects excess tissue fluid (see slide 10) and transports it back to the bloodstream Tissue fluid = similar to blood plasma but without the plasma proteins. When tissue fluid enters the lymph system it is called lymph.

59. Blood and Lymph vessels

60. Lymph System Composition
Composed of: a fluid = lymph, and a system of tubes = lymph vessels

61. Lymph
A fluid containing: lymphocytes (white blood cells) proteins and fats

62. Lymph vessels Similar to veins – thin walled Form a one way system
Have valves – function = ?
No heart – no pumping – lymph moves by contraction of body muscles
Empty lymph back into bloodstream at subclavian veins
Volume of circulating fluid in body remains fairly constant

63. The Lymph System

64. Lymph nodes
Small rounded structures found along the lymph vessels produce antibodies - destroy invading pathogens and produce and store lymphocytes (white blood cells) Lymph nodes filter the lymph as it flows through trapping and destroying bacteria

65. Functions of Lymph System
Return excess ECF to blood system - maintain balance of fluids in body = HOMEOSTASIS.
Absorb and transport fatty acids and glycerol from intestines - lacteals.
Produce lymphocytes.
Produce antibodies.
Remove and destroy bacteria.
Transport hormones.

66. END