Explain venous pulsation?

Venous Pulsation: Normally the jugular venous pulsation faithfully reflects the pressure changes in right atrium. It is described as a, x, c, x, v, y, x and x and y being descent and a and v are waves. The 'a' wave is products by atrial contraction and as atrial relaxation sets in x descent begins which is interrupted by a small 'c' wave and further descent occurs due to downward displacement of atrioventricular ring and termed as x descent to differentiate it from x descent caused by atrial relxation. The 'c' wave is produced in atrium by the closure of atrioventricular valve but in JVP in neck it is an artifact resulting from systolic thrust of carotid artery, hence named as 'c' by Mckenzie. As the ventricular contraction continues the a-v valve remains closed and venous returns continues producing another slow undwelling wave called 'v' wave. At the diastole sets in the a-v valve opens producing 'y' descent until diastesis, i.e, equalisation of pressure in atrium and ventricle occurs to be followed by atrial contraction to produce 'a' wave of another cardiac cycle. The x descent is normally brisk and easy to identify in JVP. Similarly 'a' wave is brisk event, as caused by active atrial contraction and 'v' is a slow filling wave. In case of difficulty it can be timed with contralateral carotid arlery palpation, 'a' always occurs before carotid pulsation while 'v' wave appears after this.

Figure (a): Measurement of the Figure jugular venous pulse

(b): JVP waveforms