1. Heart & Circulation

2. Circulation
The human circulatory system consists of 96,000 km of blood vessels that transport blood to each cell in the body. Your entire blood volume (about 5L) is pumped every minute.

3. The circulatory system performs the following functions:
1. carries oxygen and nutrients to the cells
2. carries carbon dioxide and waste away from the cells
3. carries hormones to target organs
4. distributes heat throughout the body
5. helps defense of invading micro-organisms

4. Blood Vessels
Arteries – carry blood away from the heart. Their thick walls are composed of three distinct, elastic layers. Each time the heart pumps, the arteries stretch to accommodate the rush of blood. This is felt in the neck, or on the wrist as a pulse.
Arterioles - are smaller arteries whose middle layer is composed of elastic fibers and smooth muscle. The arterioles are able to contract and relax, controlling blood flow to different parts of the body.

5. Vasoconstriction – the narrowing of blood vessels, decreasing flow to the tissues.

6. Capillaries – are tiny blood vessels composed of a single layer of cells. This is the site of fluid and gas exchange between the cells and the body tissues. Many capillaries are only as thick in diameter as one red blood cell (<0.005 mm). Pressure in the capillaries is high, increasing the risk of rupturing and causing a bruise.

7. Venules – larger blood vessels that form as capillaries merge
Venules – larger blood vessels that form as capillaries merge. The venules are lined with smooth muscle to ensure blood continues to flow back towards the heart.
Veins – larger blood vessels that result as venules merge, take blood back towards the heart. Veins also serve as blood reservoirs, holding up to 65% of the total blood volume. Blood pressure in the veins is quite low, so the veins have uni-directional valves that ensure the one way flow of blood. Skeletal muscles also help aid venous flow. Venous pressure increases when skeletal muscles contract and push on the vein, forcing blood upwards.

8. Blood Vessels

9. Problems with blood vessels:
Aneurysm – a bulge or weakening in the wall of a blood vessel.
Atherosclerosis – degeneration of blood vessels caused by the accumulation of fat deposits (plaque) in the inner wall.

10. Bruising – rupture of capillary beds cause blood to leak into the extra-cellular space.
Varicose Veins – damage to the one-way valves in veins causes blood to pool and the veins to bulge.

11. Circulation
The heart consists of two parallel pumps. The right connects to blood vessels that circulate blood to the lungs, for oxygenation, and back to the heart. This system is called the pulmonary circulatory system. The second, left hand pump, connects blood vessels to the body and circulates blood to the body tissues. This system is called the systemic circulatory system.
One way blood flow is maintained by uni-directional valves in the heart and in the blood vessels.

12. Pulmonary System
Systemic System

13. Closed Circulation
Blood never leaves vessels

14. Double Circulatory System
In mammals, birds and reptiles, the blood is pumped twice before returning to its origin
Fish, and other lower organisms pump the blood only once

15. Four Chambered Heart
oxygenated and deoxygenated blood do not mix in the heart
septum separates the right and left sides

16. Heart Chambers The top chambers are called atria (sing. Atrium)
These collect blood from major veins and pump it into the bottom chambers

17. Ventricles Much larger and more muscular than atria
Pump blood into arteries for distribution to body (and lungs)

18. Vessels Arteries – carry blood away from heart
Veins – carry blood toward heart
Systemic circulation – blood flow to and from body organs (not lungs)
Pulmonary circulation – blood flow to and from lungs

22. Atrioventricular Valves
Separate the atria and ventricles

23. Atrioventricular valves have:
Chordae tendinae prevent flaps from everting (opening backward)
Papillary muscles to attach chordae tendinae to ventricle wall

24. The Bicuspid Valve (AV)
Also called the mitral valve
On the left side of the heart
Has two flaps

25. Tricuspid Valve (AV)
On the right side
Has three flaps

26. Semilunar Valves
At the entrance to the major arteries are smaller valves with no muscular attachments
These have three flaps each and prevent backflow into the ventricles

28. Valve movie
video

30. Pericardium
Membrane around heart which prevents friction between heart and lungs
Also helps isolate infection

31. Coronary Arteries
The aorta branches and one of the branches comes back to serve the heart muscle (myocardium)

33. Coronary Circulation
These arteries can become blocked with plaque (cholesterol and calcium deposits) and clots can occur causing:
pain: angina pectoris
Heart muscle death: myocardial infarction (heart attack)

34. Coronary Circulation

35. Risks for Heart Disease
Genetics
Male
Smoking
Obesity
Diet (saturated fat and cholesterol)
Lack of exercise

36. Heart Beats Cardiac Muscle: striated, branched
Is myogenic muscle: can contract without nerve impulse

37. Heart Beats
Chemoreceptors in aorta and carotid (neck) arteries detect high carbon dioxide levels in blood (lesser extent – oxygen is also monitored)
Cranial nerves carry this information to the heart

39. Heart Beats
The heart beat is controlled by the sympathetic (stimulating) and parasympathetic (relaxing) branches of the nervous system.

40. Heart Beats
Tempo is set by the sinoatrial node (SA node) : the pacemaker

41. Heart Beats
Electrochemical impulses from the S.A. node cause contraction of atria muscle

42. Heart Beats
the impulse travels to another cluster of nervous tissue – the Atrioventricular node (A.V. node)

43. Heart Beats
The A.V. node sends impulses through Purkinje fibers to all parts of the ventricles
Ventricles contract simultaneously

44. Heart Beats Heart muscle then ‘rests’ before the cycle begins again
‘systole’ – phase of heart contraction
‘diastole’ – phase of heart relaxation
‘lub – dub’ – heart sounds caused by valves slamming shut

45. Heart Beats Normal Heart Rate – 80 beats/minute
Bradycardia - < 50 beats/min
Tachycardia - > 100 beats/min

46. Monitoring Heart Beat EKG (or ECG) – electrocardiogram
Uses electrical activity in heart muscle to diagnose problems

47. EKG P wave – depolarization preceding atrial contraction
QRS complex – precedes ventricular
T wave – repolarization of myocardium

48. Ventricular Fibrillation

49. Defibrillator
Used to shock hearts into proper rhythm

50. Other Abnormal Rhythms
tachycardia

51. Bradycardia

52. Blood Flow in the Heart

53. Heart Technology
stethescope

54. Heart Technology
Artificial pacemakers – use batteries to produce a coordinated signal when ‘real’ pacemaker malfunctions

55. Cardiac Catheterization
a thin catheter is inserted into a blood vessel, usually an artery in the leg or arm, and passed through the blood vessel to the heart.
Dye is injected to make the coronary arteries and other structures visible on X-rays.

56. Heart Technology
Angioplasty: using a catheter and ‘balloon’ to open up blocked arteries

57. Heart Technology
Valve Replacement : routinely done to fix valves scarred by infections, etc.

58. Heart Technology
Coronary bypass: heart operation to use a vein from leg to bypass blockage

59. Heart Transplant Often miraculous results Shortage of organs
Person must take immunosupressants for life

60. Xenotransplants Dismal failures when whole heart is transplanted
Pig arteries and valves have been used for years
New genetic research hopes to produce pigs with human proteins

61. Artificial Heart
Some success as a bridge to transplant