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The Cardiovascular System

The Cardiovascular System. Part II The Heart . Heart. A hollow muscular organ Located in thorax between 2 lungs 4 chambers 4 valves 2 atria (atrium) & 2 ventricles 2 separate pumps (R & L sides) Right side receives blood from the body and sends it to the lungs ( pulmonary )

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The Cardiovascular System

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  1. The Cardiovascular System Part II The Heart

  2. Heart • A hollow muscular organ • Located in thorax between 2 lungs • 4 chambers • 4 valves • 2 atria (atrium) & 2 ventricles • 2 separate pumps (R & L sides) • Right side receives blood from the body and sends it to the lungs (pulmonary) • Left side receives blood from lungs and sends it to the body (systemic)

  3. 2 Pumps

  4. Position of Heart

  5. Pericardium • A sac that covers and surrounds the heart Pericardial cavity Cardiac Tamponade

  6. Structure of the Heart

  7. Structure of the Heart LA RA RV LV apex

  8. Apex of Heart • Part of left ventricle • Left intercostal space (ICS) 5 • Space between left ribs 5 & 6 • App. 1 inch inferior to male nipple • Location where heart is most superficial and most easily heard

  9. Apex of Heart

  10. Structure of the Heart Note the thickness of the L&R ventricles. Why?

  11. Ventricle Wall Thickness Left ventricular wall is much thicker.

  12. Structure of the Heart RA LA RV LV

  13. Structure of the Heart RA LA RV LV

  14. Valves of the Heart • 4 valves • One way flow • Leaky valve = heart murmur • 2 atrioventricular valves • 2 semilunar valves

  15. Valves of the Heart

  16. Atrioventricular Valves • Right AV valve • Between right atrium and right ventricle • Also called the tricuspid valve because it has three cusps. • Cusps close when right ventricle contracts….preventing blood from going back up into the right atrium

  17. Atrioventricular Valves Cusps attached to chordae tendineae Chordae tendineae attached to papillary muscles Papillary muscles part of ventricular wall

  18. Atrioventricular Valves • Left AV valve • Between the left atrium and the left ventricle • Also called the bicuspid valve because it only has two cusps • Also called the mitral valve • Cusps close when left ventricle contracts….preventing blood from back up into the left atrium

  19. Atrioventricular Valves So…where does blood go when it leaves the ventrilces?

  20. Semilunar Valves

  21. Semilunar Valves • Pulmonary semilunar valve • When right ventricle contracts, blood is forced through this valve to enter pulmonary trunk • Aortic semilunar valve • When left ventricle contracts, blood is forced through this valve to enter the aorta

  22. Semilunar Valves

  23. Structure of the Heart

  24. The Cardiac Cycle • Heart beats ~ 1/sec. In that second, all 4 chambers must contract (systole) and relax (diastole) • 4 chambers….in which sequence do they contract? • 2 atria contract first (superior half of heart) and simultaneously • While the atria are contracting, the ventricles are relaxing (in order to receive the blood from the atria) • Ventricles fill and then they contract while the atria are relaxing and filling with blood. • How does the heart know how to do this?

  25. Conduction System of the Heart

  26. Conduction System of the Heart • Sino-atrial node (SA node…aka pacemaker) is located in superior wall of right atrium • It consists of nerve cells that generate and fire off an electrical impulse ~ 1/sec

  27. SA node

  28. Conduction System of the Heart • Electrical impulses from SA node then follow preferential pathways through the heart • Electrical activity first goes to both atria

  29. Conduction System of the Heart

  30. Atrioventricular Node • After causing contraction of atrial muscles, electrical current goes to the atrioventricular node (AV node) • AV node is located on the inferior wall of the right atrium.

  31. AV node From AV node, electrical activity enters AV bundle AV bundle the splits into R&L bundle branches which then cause ventricles to contract

  32. Oxygen to the heart muscles • The heart requires a significant amount of O2 • Where does the oxygen come from? • Coronary arteries..2 of them R&L • But each artery immediately branches into 2 other arteries. • Cardiologists will tell you that you have 4 coronary arteries.

  33. Coronary Arteries Atherosclerosis is an accumulation of fat on the inner walls of arteries. When coronary arteries become partially blocked….angina When coronary arteries become significantly blocked….myocardial infarction

  34. Myocardial Infarction • Without oxygen, heart cells die (MI) or heart attack. • Read p. 562 and look and the figures to observe normal and obstructive blood flow through the coronary arteries.

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