1. Chapter 15 Cardiovascular System

2. Structure of the Heart
Hollow, cone shaped, muscular pump
Size and Location of the Heart
Average size about 14cm long and 9cm wide
Bordered laterally by the lungs, posteriorly by the spinal cord, and anteriorly by the sternun
Distal end extends downward and to the left (apex)

3. Location of Heart

4. Size of Heart
Average Size of Heart
14 cm long
9 cm wide

5. Coverings of the Heart
Pericardium – outer fibrous bag that encloses heart and the proximal ends of large blood vessels attached to heart
- surrounds a more delicate double layered sac
- inner layer (epicardium) covers the heart

6. Coverings of Heart

7. Wall of the Heart Epicardium – protective outer covering that secretes
Serous fluid
Myocardium - middle layer made mostly of muscle that
pumps blood out of the heart chambers
Endocardium – inner layer that lines all heart chambers
and covers the valves

8. Wall of the Heart

9. Wall of the Heart

10. Heart Chambers and Valves
4 hollow chambers (2 left and 2 right)
Upper chambers (atria) are thin walled and receive blood returning to the heart
Lower chambers (ventricles) are more muscular and force blood out of the heart into arteries
Valves of the Heart -tricuspid, pulmonary, bicuspid (mitral), aortic – Table 15.2 Page 561

11. Mitral valve prolapse (Page 558) – mitral valve stretches and bulges into left atrium during contraction causing blood to sometimes regurgitate into left atrium
Chordae tendinae are tough fibrous strings attached to papillary muscle that prevent tricuspid and bicuspid valves from swinging back into atrium

12. Heart Valves
Tricuspid Valve
Pulmonary and Aortic Valve

13. Heart Valves

14. Skeleton of Heart
fibrous rings to which the heart valves are attached

15. Structure of the Heart

16. Path of Blood Through the Heart

17. Path of Blood Through the Heart

18. Blood Supply to the Heart
First two branches of the aorta (coronary arteries) supply blood to the tissues of the heart – Fig Page 565
Branches of the coronary veins drain blood from heart tissues – they join the coronary sinus and empty into the right atrium

19. Blood Supply to Heart

20. Angiogram of Coronary Arteries

21. Heart Actions
Cardiac Cycle = atria contract while ventricles relax, ventricles contract while atria relax, atria and ventricles relax for a moment

22. Heart Actions Atrial Diastole/Ventricular Systole
Atrial Systole/Ventricular Diastole
Atrial Diastole/Ventricular Systole

23. Cardiac Cycle
A-V valves = atrioventricular valves (tricuspid and bicuspid)
During cycle pressure within chambers rises and falls
Pressure increases as chambers fill
Blood flows into atria when relaxed, A-V valves open when pressure is greater than in ventricles

24. Atria contract forcing remaining blood into ventricles (30%)
Atrial relaxation follows (diastole)
As ventricles contract A-V valves close (systole)
Pulmonary and aortic valves open and blood is ejected into arteries (aorta or pulmonary)
When ventricles relax A-V valves open and ventricles begin to fill with blood again

25. Heart Sounds Through a stethescope it sounds like lubb – dupp
Blood flow through chambers and opening and closing of valves causes vibrations
Lubb sound occurs during ventricular contraction (systole) when A-V valves are closing
Dupp sound occurs during ventricular relaxtion (diastole) when A-V valves are closing

26. Heart sounds can indicate condition of heart valves condition
Ex: valve cusps may not close completely causing a murmur – many are harmless, most serious problems can be repaired or the
valve replaced
Can hear heart sounds associated with each valve – fig page 569

27. Heart Sounds

28. Cardiac Muscle Fibers
A functional syncytium is a mass a of merging cells that act a unit
Heart has 2 units
atrial syncytium – walls of atria
ventricular syncytium- wall of ventricles
units are connected by fibers of the cardiac conduction system in a small area of right atrial floor

29. Muscle Fibers in Ventricular Walls

30. Cardiac Conduction System
S-A node
small mass of cardiac muscle tissue beneath the epicardium that initiate and distribute impulses throughout the myocardium
can reach threshold on its own without stimulation from nerve fibers
generates the heart’s rhythmic activity (70-80 times / min)
often called the pacemaker
right and left atria contract almost simultaneously

31. A-V node Impulses from S-A node pass slowly to A-V node
Impulses then travel rapidly along A-V bundle and Purkinje fibers stimulating ventricles to contract
See fig page 570 – locations
See fig page 570 – pathway

32. Electrocardiogram (ECG)
Recording of electrical changes that occur in the myocardium during a cardiac cycle
Used to assess heart’s ability to conduct impulses
Electrodes are placed on the skin to record
Normal ECG fig page 572
P wave – deplolarization of atria
QRS complex – depolarization of ventricles
T wave – repolarization of ventricles

33. Cardiac Conduction System

34. Cardiac Conduction System

35. Electrocardiogram

36. Electrocardiogram

37. Cardiac Cycle

38. Clinical Application Arrhythmias Ventricular fibrillation Tachycardia
rapid, uncoordinated depolarization of ventricles
Tachycardia
rapid heartbeat
Atrial flutter
rapid rate of atrial depolarization

39. Regulation of Cardiac Cycle
Physical exercise and elevated body temperature increase heart action
Vagus nerves (parasympathetic fibers) secrete Ach
which decrease S-A and A-V activity – heart rate decreases
K ions affect the electrical potential of cell membranes
Ca ions needed for muscle contraction
Clinical application 15.2 page 574 – arrhythmias

40. Regulation of Cardiac Cycle
Autonomic nerve impulses alter the activities of the S-A and A-V nodes

41. Blood Vessels Table 15.3 Page 581- characteristics of blood vessels
Fig walls of an artery and vein
15.26 Page 576 – walls of arterioles
fig page 578 walls of capillaries

42. Characteristics of Blood Vessels

43. Walls of Artery and Vein

44. Arteriole smallest arterioles only have a few smooth muscle fibers
capillaries lack muscle fibers

45. Metarteriole
connects arteriole directly to venule

46. Capillaries smallest diameter blood vessels
extensions of inner lining of arterioles
walls are endothelium only
semipermeable
sinusoids – leaky capillaries

47. Capillary Network

48. Regulation of Capillary Blood Flow
Precapillary sphincters
may close a capillary
respond to needs of the cells
low oxygen and nutrients cause sphincter to relax

49. Exchange in the Capillaries
water and other substances leave capillaries because of net outward pressure at the capillaries’ arteriolar ends
water enters capillaries’ venular ends because of a net inward pressure
substances move in and out along the length of the capillaries according to their respective concentration gradients

50. Venules and Veins Venule thinner wall than arteriole
less smooth muscle and elastic tissue than arteriole
Vein
thinner wall than artery
three layers to wall but middle layer is poorly developed
some have flaplike valves
carries blood under relatively low pressure
serves as blood reservoir

51. Venous Valves

52. Blood Volumes in Vessels

53. Blood Pressure force blood exerts against the inside of blood vessels
Arterial Blood Pressure
Rises and falls with the phases of the cardiac cycle
Systolic pressure is the maximum pressure achieved during ventricular contraction
Diastolic pressure is the lowest pressure that remains in the arteries when the ventricles relax

54. Blood pressure measurement is reported as a fraction
SP/DP in mm Hg using a sphygmomanometer
Pulse is the expanding and recoiling of the arterial wall
Can be felt in several arteries – fig page 585

55. Factors That Influence Arterial Blood Pressure
Heart Action
Cardiac output = stroke volume (blood discharged per contraction) x heart rate
BP rises as cardiac output rises

56. Blood volume
BP is directly proportional to blood volume
Peripheral Resistance
Friction between the blood and walls of blood vessels
Dilation of arterioles lessens resistance and lowers BP
Constriction of arterioles increases resistance and raises BP

57. Viscosity
The ease with which molecules flow past one another
The greater the viscosity the greater the resistance to flowing – the greater the force needed to move it
Blood cells and plasma proteins increase blood viscosity

58. Pulse
alternate expanding and recoiling of the arterial wall that can be felt

59. Factors That Influence Arterial Blood Pressure

60. Control of Blood Pressure
BP = CO (cardiac output) x PR(peripheral resistance)
CO depends on volume of blood discharged
Cardiac center of the medulla oblongata regulates heart rate
Changes in the diameter of arterioles regulate PR
controlled by the vasomotor center of the medulla oblongata

61. Control of Blood Pressure
If blood pressure rises, baroreceptors initiate the cardioinhibitory reflex, which lowers the blood pressure

62. Control of Blood Pressure
Dilating arterioles helps regulate blood pressure

63. Venous Blood Flow Not a direct result of heart action
Depends on skeletal muscle contraction, breathing, movements, and vein constriction (venoconstriction)
Many veins have valves that prevent backflow
Veins provide a blood reservoir

64. Venous Blood Flow

65. Central Venous Pressure
Pressure in right atrium
Affects pressure in veins – if heart is beating weakly CVP increases, blood backs up in the venous network and its pressure rises

66. Exercise and the Cardiovascular System
Page 593 clinical application 15.7

67. Paths of Circulation Pulmonary Circuit
Consists of vessels that carry blood from the heart to the lungs and back to the heart
Fig page 594

68. Pulmonary Circuit
consists of vessels that carry blood from the heart to the lungs and back to the heart

69. Systemic Circuit
Carries blood from the heart to all other parts of the body and back again
Fig page 594

70. Arterial System Aorta is the largest artery in the body
3 major arteries originate from the branch of the aorta
major arteries to know: common carotid, brachiocephalic, subclavian, brachial, renal, abdominal, coronary, external iliac, femoral

71. Major Vessels of Arterial System

72. Major Blood Vessels of the Heart

73. Principal Branches of the Aorta

74. Abdominal Aorta and Its Major Branches

75. Arteries to Neck, Head, and Brain

76. Cerebral Arterial Circle
Circle of Willis
formed by anterior and posterior cerebral arteries, which join the internal carotid arteries

77. Venous System
returns blood to the heart after gases, nutrients, and wastes are exchanged between blood and cells
major veins to know: internal jugular, subclavian, inferior vena cava, superior vena cva, renal, external iliac, femoral, brachial,

78. Major Vessels of the Venous System

79. Major Veins of the Brain, Head and Neck

80. Veins That Drain the Abdominal Viscera

81. Life-Span Changes cholesterol deposition in blood vessels
heart enlargement
death of cardiac muscle cells
increase in fibrous connective tissue of the heart
increase in adipose tissue of the heart
increase in blood pressure
decrease in resting heart rate