The pericardium is a double-walled sac that surrounds and protects the heart.
True
False
The Correct Answer is A
Correct answer: True
The pericardium is a fibroserous, double-walled sac located in the mediastinum that encloses the heart and the roots of the great vessels. It consists of an outer fibrous layer that provides structural support and limits excessive cardiac movement, and an inner serous layer, which is divided into parietal and visceral layers separated by a small amount of pericardial fluid. This fluid acts as a lubricant, reducing friction as the heart contracts and relaxes. The pericardium’s anatomical position and structure protect the heart from mechanical injury, infection, and sudden overexpansion, while maintaining optimal conditions for cardiac function.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. The volume of blood remaining in the ventricle after ventricular systole: This refers to the end-systolic volume (ESV), which is the amount of blood left in the ventricle after contraction. While ESV is a component used to calculate stroke volume, it does not itself represent the volume of blood ejected with each heartbeat.
B. The pressure exerted by the left ventricle to open the aortic valve: The pressure generated by the left ventricle during systole is termed ventricular systolic pressure. Although this pressure must overcome aortic pressure to allow ejection, it is a measure of force, not volume, and therefore does not define stroke volume.
C. The difference between end-diastolic volume (EDV) and end-systolic volume (ESV): Stroke volume represents the actual volume of blood ejected from the ventricle with each heartbeat. It is calculated as SV = EDV – ESV. EDV is the total ventricular volume at the end of filling, and ESV is the residual volume after contraction. This difference reflects effective cardiac output per beat.
D. The total volume of blood in the ventricle before contraction: The total volume of blood prior to contraction is the end-diastolic volume (EDV). While EDV contributes to determining stroke volume, it alone does not represent the volume of blood expelled during systole.
Correct Answer is D
Explanation
A. P wave:: The P wave represents atrial depolarization, indicating electrical activation of the atria. It precedes atrial contraction and is the first deflection on a standard ECG tracing. Normal duration is ≤0.12 seconds.
C. T wave: The T wave reflects ventricular repolarization, showing the recovery phase of the ventricles after contraction. Its shape and amplitude can indicate electrolyte imbalances, ischemia, or other cardiac abnormalities.
F. QT segment: The QT segment (more accurately called the QT interval), labelled as F, represents the total time for ventricular depolarization and repolarization. It begins at the start of the QRS complex and ends at the conclusion of the T wave on an electrocardiogram (ECG). It reflects the entire period of ventricular electrical activity, including contraction and recovery.
D. PR interval: The PR interval represents the time for electrical conduction from the atria through the AV node to the ventricles. Normal duration is 0.12–0.20 seconds, with prolongation suggesting conduction delay.
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