What is the primary function of the myocardium?
To contract and generate force for blood circulation
To produce pericardial fluid
To protect the heart from external injury
To facilitate the electrical conduction in the heart
The Correct Answer is A
A. To contract and generate force for blood circulation:
The myocardium is the muscular layer of the heart wall responsible for contracting and generating pressure to circulate blood through the systemic and pulmonary circuits. Its thickness varies by chamber, with the left ventricle being the thickest due to the higher pressure required to pump blood systemically. Dysfunction in the myocardium leads to heart failure or arrhythmias.
B. To produce pericardial fluid:
The pericardium, not the myocardium, secretes pericardial fluid to reduce friction during cardiac movement. Confusing these structures may lead to misunderstanding cardiac physiology.
C. To protect the heart from external injury:
Protection is primarily provided by the pericardium and thoracic cage. The myocardium’s main role is mechanical contraction, not external protection.
D. To facilitate the electrical conduction in the heart:
Electrical conduction is carried out by specialized nodes and fibers (SA node, AV node, bundle of His, Purkinje fibers). The myocardium responds to these signals but does not generate the primary conduction itself.
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Related Questions
Correct Answer is D
Explanation
A. To pump blood to the lungs for oxygenation:
The right ventricle pumps deoxygenated blood to the lungs. The left ventricle is responsible for systemic circulation.
B. To receive deoxygenated blood from the body:
The right atrium receives deoxygenated blood from the systemic veins.
C. To regulate heart rhythm:
Heart rhythm is controlled by the SA and AV nodes and the conduction system, not the ventricles themselves.
D. To pump oxygenated blood into systemic circulation:
The left ventricle has thick muscular walls that generate the high pressure needed to pump oxygen-rich blood through the aorta and systemic arteries to the entire body. Dysfunction leads to decreased perfusion and signs of left-sided heart failure.
Correct Answer is C
Explanation
A. They are responsible for the contraction of the heart muscle:
Contraction is a function of the myocardium, not the arteries. Coronary arteries provide oxygen and nutrients, enabling contraction but do not generate force themselves.
B. They carry deoxygenated blood away from the heart muscle:
Coronary veins, not arteries, drain deoxygenated blood from the myocardium into the coronary sinus.
C. They supply oxygenated blood to the heart muscle:
Coronary arteries deliver oxygen-rich blood to the myocardium, ensuring the heart has the energy and oxygen needed for continuous contraction. Occlusion of these arteries can lead to myocardial infarction.
D. They regulate the heart's electrical impulses:
Electrical impulses are conducted via the SA node, AV node, bundle of His, and Purkinje fibers, not the coronary arteries.
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