What is the function of the pericardial sac surrounding the heart?
To regulate heart rate
To contract and assist with blood pumping
To provide a lubricated environment for the heart
To store blood during diastole
The Correct Answer is C
A. To regulate heart rate:
Heart rate is controlled by the SA node and autonomic nervous system, not the pericardial sac.
B. To contract and assist with blood pumping:
The pericardium is non-contractile; it does not generate force to pump blood.
C. To provide a lubricated environment for the heart:
The pericardial sac contains pericardial fluid that reduces friction between the heart and surrounding structures during contraction and relaxation, protecting the heart from mechanical stress.
D. To store blood during diastole:
The pericardium does not store blood; ventricular chambers store blood transiently during diastole.
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Related Questions
Correct Answer is A
Explanation
A. Ventricular systole:
Semilunar valves (aortic and pulmonic) open when ventricular pressure exceeds arterial pressure during systole, allowing blood to be ejected into the aorta and pulmonary artery.
B. Isovolumetric relaxation:
During this phase, the ventricles relax and pressure falls, causing the semilunar valves to close to prevent backflow.
C. Atrial systole:
During atrial contraction, the AV valves are open to fill the ventricles; semilunar valves remain closed.
D. Ventricular diastole:
During diastole, the ventricles fill with blood, and the semilunar valves remain closed until the next systole.
Correct Answer is D
Explanation
A. Increase cardiac output by stretching the ventricles:
Stretching of the ventricles relates to preload, but papillary muscles and chordae tendineae do not directly stretch the ventricles to increase output.
B. Facilitate rapid conduction of electrical impulses:
Electrical conduction is carried by the SA node, AV node, bundle of His, and Purkinje fibers, not the papillary muscles or chordae tendineae.
C. Assist in opening the semilunar valves:
Semilunar valves (aortic and pulmonic) open due to ventricular pressure exceeding arterial pressure, not through papillary muscle function.
D. Prevent valve prolapse during ventricular contraction:
The papillary muscles contract during ventricular systole, pulling on the chordae tendineae, which anchor the mitral and tricuspid valves. This prevents backflow of blood into the atria (valve prolapse) and ensures efficient unidirectional flow.
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