Heart Rests On The Superior Surface Of The Heart

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Pg 692 Review Questions 10-20
10. The heart rests on the superior surface of the diaphragm and lies anterior to the vertebral column. It is posterior to the sternum with the lungs flanking it on either side. Roughly two-thirds of its mass lies to the left of the midsternal line. It is enclosed within the mediastinum and extends obliquely for 12-14 cm from the second rib to the fifth intercostal space.
11. The pericardium is a double-walled sac that encloses the heart. The fibrous pericardium is the loosely fitting superficial part of the sac. It is a tough, dense connective tissue layer that protects the heart, anchors it to surrounding structures and prevents overfilling of the heart with blood. The serous pericardium is deep to the fibrous pericardium. It is a thin, slippery, two-layer serous membrane. Its parietal layer lines the internal surface of the fibrous pericardium and attaches to the large arteries, exciting the heart.
12. Blood returns from the body oxygen-poor and carbon dioxide-rich. The blood enters the right atrium and passes into the right ventricle, which pumps it into the lungs via the pulmonary trunk. Once in the lungs, the blood unloads carbon dioxide and picks up oxygen. The blood is then carried by the pulmonary veins back to the left side of the heart. This is called the pulmonary circuit.
13. (a). the coronary arteries deliver blood when the heart is relaxed, but are rather ineffective when the ventricles are contracting because they are compressed by the contracting myocardium.
(b). The anterior interventricular artery supplies blood to the interventricular septum and anterior walls of both ventricles. The circumflex artery supplies the left atrium and posterior walls of the left ventricle. The right marginal artery serves the myocardium of the lateral right side of the heart. The posterior interventricular artery runs to the heart apex and supplies the posterior ventricular walls.
14. The long refractory period normally prevent titanic contractions, which would stop the hearts pumping action.
15. (a). The SA node or pacemaker, the AV node, the AV bundle, the bundle branches, and the Purkinje fibers.
(b). The intrinsic cardiac conduction system depolarizes and contracts the heart in an orderly and sequential manner so the heart beats as a coordinated unit.
16.
The P wave results from movement f the depolarization wave from the SA node through the atria. The QRS complex results from ventricular depolarization and precedes ventricular contraction. The T wave is caused by ventricular repolarization.
17. The cardiac cycle includes all events associated with the blood flow through the heart during one complete heartbeat. It begins with Ventricular filling (mid-to-late diastole) and Atrial contraction. It then moves onto ventricular systole which consists of isovolumetric contraction phase and ventricular ejection phase. It then ends with early diastole which involves isovolumetric relaxation and ventricular filling.
18. Cardiac output, which is typically 5L/min, is the amount of blood pumped out by each ventricle in 1 minute. Cardiac output= heart rate X stroke volume.
19. According to Frank-Starling law of the heart, the critical factor controlling SV is the preload, which is the degree to which cardiac muscles are
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