The mitral and tricuspid valves close after the ventricles are filled with blood because the
Chordae tendineae relax, which allows the valves to close.
Increased pressure in the ventricles pushes the valves to close.
Trabeculae carneae contract, which pulls the valves closed.
Reduced pressure in the atria creates a negative pressure that pulls the valves closed.
The Correct Answer is B
The mitral and tricuspid valves are located between the atria and ventricles in the heart, and they open and close to allow blood to flow in one direction through the heart. During diastole, when the heart is relaxed and filling with blood, the mitral and tricuspid valves are open to allow blood to flow from the atria into the ventricles.
Once the ventricles are filled with blood, they begin to contract during systole to pump the blood out to the lungs (right ventricle) and the rest of the body (left ventricle). As the ventricles contract, the pressure within them increases, which causes the mitral and tricuspid valves to be pushed closed by the blood within the ventricles. This closure prevents the backflow of blood into the atria during ventricular contraction (systole).
The chordae tendineae are thin, fibrous cords that connect the mitral and tricuspid valves to the papillary muscles within the ventricles. These structures help to anchor the valves in place during ventricular contraction, and prevent them from prolapsing (bulging back into the atria) and causing regurgitation (backflow of blood).
The trabeculae carneae are muscular ridges within the ventricles that help to increase the force of ventricular contraction, but they do not play a direct role in closing the mitral and tricuspid valves. Similarly, the reduced pressure in the atria during ventricular contraction is due to the fact that blood is being pumped out of the atria and into the ventricles, rather than the atria "pulling" the valves closed.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
The walls of the atria are thin because they do not generate as much pressure as the ventricles, as their main function is to receive blood from the veins and pump it into the ventricles. The ventricles have thicker walls because they are responsible for generating the force necessary to pump blood out of the heart and into the systemic or pulmonary circulation.
Correct Answer is C
Explanation
The left ventricle is responsible for pumping oxygenated blood out of the heart and into systemic circulation, which requires generating enough pressure to overcome the resistance of the systemic blood vessels. Therefore, the left ventricle has thicker and more muscular walls than the right ventricle and can generate higher pressures during contraction. In contrast, the right ventricle pumps deoxygenated blood to the lungs, which have lower resistance compared to the systemic circulation, and therefore do not need to generate as high pressures.
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