Heart Anatomy and Function: Key Concepts for Students

1. What is the approximate size of the heart

About the size of your fist.

2. Where is the heart located

In the mediastinum, between the 2nd rib and 5th intercostal space, on top of the diaphragm.

3. Which side of the body is most of the heart on

About 2/3 is left of the midsternal line.

4. What is the orientation of the heart

It is anterior to the vertebral column and posterior to the sternum. The apex points downward.

5. What are the coverings of the heart

The pericardium, which includes the fibrous pericardium and serous pericardium.

6. What is the function of the fibrous pericardium

Protects the heart, anchors it to surrounding structures, and prevents overfilling.

7. What are the two layers of the serous pericardium

Parietal layer and visceral layer.

8. What is the visceral layer of the serous pericardium also called

The epicardium.

9. What is the pericardial cavity

The fluid-filled space between the parietal and visceral layers that decreases friction.

10. What are the three layers of the heart wall

Epicardium, myocardium, and endocardium.

11. What is the epicardium

The visceral layer of the serous pericardium.

12. What is the myocardium

The middle layer made of cardiac muscle that contracts to pump blood.

13. What is the endocardium

The inner layer that lines the heart chambers and is continuous with the lining of blood vessels.

14. What is the cardiac skeleton

A layer of connective tissue that anchors cardiac muscle fibers and supports the great vessels and valves.

15. What are the two upper chambers of the heart

Right atrium and left atrium.

16. What are the two lower chambers

Right ventricle and left ventricle.

17. What separates the right and left atria

The interatrial septum.

18. What separates the right and left ventricles

The interventricular septum.

19. What does the right atrium receive

Oxygen-poor blood from the body through the superior vena cava, inferior vena cava, and coronary sinus.

20. Where does blood go after the right atrium

Through the tricuspid valve into the right ventricle.

21. What does the right ventricle do

Pumps oxygen-poor blood through the pulmonary valve into the pulmonary trunk and pulmonary arteries.

22. Where does the pulmonary circuit take blood

To the lungs to become oxygenated.

23. What does the left atrium receive

Oxygen-rich blood from the lungs through the four pulmonary veins.

24. Where does blood go after the left atrium

Through the mitral valve into the left ventricle.

25. What does the left ventricle do

Pumps oxygen-rich blood through the aortic valve into the aorta and then to the body.

26. Which ventricle has the thicker wall

The left ventricle.

27. Why is the left ventricle thicker

It has to pump blood through the longer, higher-pressure systemic circuit.

28. What is the purpose of heart valves

To ensure one-way blood flow through the heart.

29. What are the two AV valves

Tricuspid and mitral (bicuspid).

30. Where is the tricuspid valve

Between the right atrium and right ventricle.

31. Where is the mitral valve

Between the left atrium and left ventricle.

32. What do AV valves prevent

Backflow into the atria when the ventricles contract.

33. What are chordae tendineae

Fibrous cords that anchor the AV valve cusps to papillary muscles.

34. What do papillary muscles and chordae tendineae do

They prevent the AV valve flaps from turning inside out during ventricular contraction.

35. What are the two semilunar valves

Pulmonary valve and aortic valve.

36. Where is the pulmonary valve

Between the right ventricle and pulmonary trunk.

37. Where is the aortic valve

Between the left ventricle and aorta.

38. What do semilunar valves prevent

Backflow into the ventricles when the ventricles relax.

39. What is the complete pathway of blood through the heart

Body → SVC/IVC/coronary sinus → right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary trunk → pulmonary arteries → lungs → pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve → aorta → body.

40. What is the pulmonary circuit

The circuit from the right side of the heart to the lungs and back to the left side.

41. What is the systemic circuit

The circuit from the left side of the heart to the body and back to the right side.

42. Which side of the heart pumps oxygen-poor blood

Right side.

43. Which side pumps oxygen-rich blood

Left side.

44. What are the major characteristics of cardiac muscle cells

Striated, short, branched, interconnected, and usually have one central nucleus.

45. What are intercalated discs

Junctions between cardiac muscle cells.

46. What do desmosomes do

Prevent cardiac muscle cells from separating during contraction.

47. What do gap junctions do

Allow ions to pass from cell to cell, electrically connecting the cells.

48. What does it mean that the heart acts as a functional syncytium

The cardiac muscle cells act as one coordinated unit.

49. How is cardiac muscle different from skeletal muscle

Cardiac muscle is involuntary, has automaticity, has intercalated discs, and has a long refractory period that prevents tetanus.

50. What is automaticity/autorhythmicity

The ability of certain cardiac cells to generate their own action potentials without nervous system stimulation.

51. What percentage of cardiac cells have automaticity

About 1%.

52. Why is the long absolute refractory period important

It prevents tetanic contractions so the heart can relax and fill with blood.

53. What ion enters the cardiac muscle cell during depolarization

Na⁺ through fast voltage-gated sodium channels.

54. What happens after the depolarization wave reaches the T tubules

The sarcoplasmic reticulum releases Ca²⁺.

55. What does Ca²⁺ bind to

Troponin.

56. What happens when Ca²⁺ binds to troponin

The filaments slide and the muscle contracts.

57. What causes the plateau phase of a cardiac action potential

Ca²⁺ enters through slow calcium channels.

58. Why is the plateau phase important

It prolongs the action potential and contraction, allowing enough time for blood to be ejected.

59. What causes repolarization

Ca²⁺ channels close and K⁺ channels open, allowing K⁺ to leave the cell.

60. What is the intrinsic cardiac conduction system

The heart's internal system that generates and spreads electrical impulses.

61. What is the correct conduction pathway

SA node → AV node → AV bundle → right and left bundle branches → Purkinje fibers.

62. What is the SA node

The heart's pacemaker, located in the right atrial wall.

63. What does the SA node do

Generates impulses that determine the heart's rhythm.

64. What is the normal intrinsic rate of the SA node

About 100 beats/minute, but it is normally tempered to about 75 beats/minute.

65. Where is the AV node located

In the inferior interatrial septum.

66. What does the AV node do

Delays the impulse about 0.1 second so the atria can contract before the ventricles.

67. What is the intrinsic rate of the AV node

About 50 beats/minute.

68. What is the AV bundle (bundle of His)

The only electrical connection between the atria and ventricles.

69. What do the bundle branches do

Carry impulses through the interventricular septum toward the apex.

70. What are Purkinje fibers

The subendocardial conducting network that spreads the impulse through the ventricular walls.

71. What direction does ventricular contraction occur

From the apex toward the atria.

72. What is an ECG/EKG

A recording of the electrical activity of the heart.

73. What does the P wave represent

Atrial depolarization.

74. What does the QRS complex represent

Ventricular depolarization and atrial repolarization.

75. What does the T wave represent

Ventricular repolarization.

76. What happens at the AV node during the ECG

The impulse is briefly delayed after atrial depolarization.

77. What does the PR interval represent

The time from the beginning of atrial depolarization to the beginning of ventricular depolarization.

78. What does the ST segment represent

The period when the ventricles are fully depolarized.

79. What does the QT interval represent

The time associated with ventricular depolarization and repolarization.

80. What causes the first heart sound, "lub"

Closure of the AV valves.

81. When does "lub" occur

At the beginning of ventricular systole.

82. What causes the second heart sound, "dup"

Closure of the semilunar valves.

83. When does "dup" occur

At the beginning of ventricular diastole.

84. What is a heart murmur

An abnormal heart sound, usually caused by an incompetent or stenotic valve.

85. What is the cardiac cycle

The blood flow and pressure changes during one complete heartbeat.

86. What is systole

Contraction.

87. What is diastole

Relaxation.

88. What happens during ventricular filling

AV valves are open and blood flows into the ventricles.

89. What percentage of ventricular filling happens passively

About 80%.

90. What does atrial systole contribute

The remaining 20% of ventricular filling.

91. What is EDV

End-diastolic volume—the amount of blood in a ventricle at the end of ventricular diastole.

92. What happens during ventricular systole

The ventricles contract, AV valves close, and blood is eventually ejected through the semilunar valves.

93. What is isovolumetric contraction

The ventricles are contracting while all four valves are closed.

94. When do the semilunar valves open

When ventricular pressure becomes greater than pressure in the arteries.

95. What is ESV

End-systolic volume—the amount of blood remaining in a ventricle after systole.

96. What is isovolumetric relaxation

The ventricles relax while all valves are temporarily closed.

97. When do the AV valves open again

When atrial pressure becomes greater than ventricular pressure.

98. What is cardiac output

The volume of blood pumped by each ventricle in one minute.

99. What is the cardiac output formula

CO = HR × SV