This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Medicine
'C' wave in JVP is due to 
Select and explain. 
A. Atrial contraction, B. Tricuspid valve bulging into right atrium, C. Right atrial filling, D. Rapid ventricular filling
B: Tricuspid valve bulging into right atrium
Answer: B: Tricuspid valve bulging into right atrium 
Explanation: Ans. is 'b' i.e., Tricuspid valve bulging into right atrium The Jugular venous pulse (JVP) reflects phasic pressure changes in the right atrium and it consists of three positive waves and two negative troughs.It will be useful to keep in mind the events of the cardiac cycle while evaluating Jugular venous pulse.JUGULAR VENOUS PULSE. a waveIt is the positive presystolic wave produced by right atrial contraction.x descenta wave is followed by the negative systolic wave the 'x' descent.The x descent is produced due to atrial relaxation Q.The atrial relaxation is produced as a result of ventricular contraction.c waveThe x descent is interrupted by second positive wave the 'c' wave.It is produced by bulging of the tricuspid valve into the right atrium Q during RV isovolumetric contraction.v waveIt is the positive systolic wave.It result from increase in the blood volume in the vena cava during systole, when the tricuspid valve is closed Q.y descentFollowing the "v wave" this is a negative descending limb referred to as the y descent or diastolic collapse Q.It is due to tricuspid valve opening and rapid inflow of blood into the right ventricle.So there areThree visible major positive waves (a, c and v) andTwo negative waves (x and y).