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Ch. 18 The Cardiovascular System: The Heart
Marieb - Human Anatomy & Physiology 11th Edition
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034Not the one you use?Change textbook
All textbooksMarieb, Hoehn 11th EditionCh. 18 The Cardiovascular System: The HeartProblem 18
Chapter 18, Problem 18

Describe how heart contraction and relaxation influence coronary blood flow
Name the major branches of the coronary arteries, and note the heart regions served by each

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1
Understand that coronary blood flow is influenced by the phases of the cardiac cycle: systole (heart contraction) and diastole (heart relaxation). During systole, the myocardium contracts, compressing the coronary vessels and reducing blood flow, especially in the subendocardial regions.
During diastole, the heart muscle relaxes, relieving pressure on the coronary vessels and allowing blood to flow more freely through the coronary arteries. This phase is critical because most coronary perfusion occurs during diastole.
Identify the major branches of the coronary arteries starting with the left coronary artery (LCA), which typically divides into the left anterior descending artery (LAD) and the circumflex artery (LCx).
Note that the LAD supplies the anterior wall of the left ventricle, the anterior two-thirds of the interventricular septum, and the apex of the heart, while the circumflex artery supplies the lateral and posterior walls of the left ventricle.
Recognize the right coronary artery (RCA) as the other major branch, which supplies the right atrium, right ventricle, the posterior one-third of the interventricular septum, and often the sinoatrial (SA) and atrioventricular (AV) nodes, important for cardiac conduction.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cardiac Cycle and Coronary Blood Flow

The cardiac cycle consists of systole (contraction) and diastole (relaxation). Coronary blood flow primarily occurs during diastole because the heart muscle relaxes, reducing pressure on coronary vessels and allowing blood to perfuse the myocardium. During systole, contraction compresses coronary vessels, limiting blood flow.
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Major Coronary Arteries

The two main coronary arteries are the left and right coronary arteries. The left coronary artery branches into the left anterior descending (LAD) and circumflex arteries, while the right coronary artery (RCA) supplies other regions. These arteries deliver oxygenated blood to specific heart areas.
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Regions Supplied by Coronary Artery Branches

The LAD artery supplies the anterior wall of the left ventricle and the interventricular septum. The circumflex artery supplies the lateral and posterior walls of the left ventricle. The RCA supplies the right atrium, right ventricle, and parts of the posterior left ventricle and conduction system.
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Related Practice
Textbook Question

The activity of the heart depends on intrinsic properties of cardiac muscle and on neural factors. Thus:

a. Vagus nerve stimulation of the heart reduces heart rate

b. Sympathetic nerve stimulation of the heart decreases time available for ventricular filling

c. Sympathetic stimulation of the heart increases its force of contraction

d. All of the above

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Trace one drop of blood from the time it enters the right atrium until it enters the left atrium. What is this circuit called?

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Discuss how the Frank-Starling law of the heart helps to explain the influence of venous return on stroke volume.

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Name the elements of the intrinsic conduction system of the heart in order, beginning with the pacemaker

What is the important function of this conduction system?

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Describe the pericardium and distinguish between the fibrous and the serous pericardia relative to histological structure and location.

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