Chapter 15: The Cardiovascular System

1. Chapter 15: The Cardiovascular System Heart

2. Introduction to the Heart • Hold up your clenched fist • Your heart is about the size of your fist • Varies by gender, and age of the owner • Age changes are due to increases in the size of cells, not number of cells • Average mass of a heart  230-350 grams (0.5 – 0.8 pounds)

3. STRUCTURE AND ORGANIZATION OF THE HEART • Location and Coverings of the Heart • Heart located between two lungs in thoracic cavity • 2/3 of mass is left of body’s midline • Apex pointed end formed at tip of left ventricle • Base  formed by atria, mostly left atrium • Major blood vessels enter and exit at the base

4. Check yourself….

5. Pericardium: membrane that surrounds and protects the heart and holds it in place • Two parts of pericardium: (1) Fibrous pericardium (2) Serous pericardium

6. Inflammation of the Pericardium • Pericarditis  build up of pericardial fluid; compresses the heart = cardiac tamponade

7. Heart Wall • Three layers: • EXTERNAL (1) epicardium or visceral layer of serous pericardium • Thin, transparent outer layer of the wall • Composed of mesothelium and connective tissue

8. MIDDLE (2) myocardium • Bulk of heart wall • Consists of cardiac muscle • Responsible for pumping action of heart

9. Cardiac muscle  two separate networks connected by intercalated discs • Atrial • Ventrical • Gap junctions in the discs allow action potential conduction from one muscle fiber to the next

10. INTERNAL (3) endocardium • Thin layer of squamous epithelium lining inside of myocardium • Covers valves of heart and tendons attached to the valves • Continuous with epithelial lining of large blood vessels

11. Chambers of the Heart • Four chambers: • Two upper are the atria • Right atrium • Left atrium

12. Two lower are the ventricles • Right ventricle • Left ventricle

13. Great Vessels of the Heart • Right atrium receives deoxygenated blood through three veins… • Superior vena cava • Inferior vena cava • Coronary sinus

14. Right ventricle pumps blood into the pulmonary trunk • Right pulmonary artery goes to right lung • Left pulmonary artery goes to left lung • Blood becomes oxygenated

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17. Valves of the Heart (4) • Prevent blood from flowing backward • Composition: dense connective tissue covered by endothelium • TWO Atrioventricular (AV) valves lie between the atria and ventricles • Between the right atrium and right ventricle is the AV called the (1) tricuspid valve, which has the three cusps

18. Chordae tendineae • tendon-like chords that connect the pointed ends of the cusps to cardiac muscle projections on inner surface of the ventricles • prevent the cusps from pushing up into the atria when the ventricles contract

19. AV between the left atrium and left ventricle is called the (2) bicuspid (mitral) valve • It has two cusps

20. TWO Semilunar valves are located near origin of pulmonary trunk and aorta • Prevent blood from flowing back into the heart • Pulmonary valve • Aortic valve Both consists of three semi-lunar cusps attached to the artery wall