The jugular vein has a pulse which results from contraction of the heart, but the pulse is conveyed through them in a retrograde manner, unlike that in the arteries (Figure 14). This pulse (wave) can be sensed at the jugular vein, and has been used for timing cardiac events in the assessment of ventricular performance.
The a wave results from right atrial contraction, producing a wave that moves backward into the veins. It occurs simultaneously with S1 and with the QRS complex. Recall that no valve guards the vena caval-atrial orifice. There was a valve at that location in early embryonic development, but it later disappeared, leaving the sinoatrial node. The pressure then falls in the jugular completing the a wave. Pressure then rises in a c wave.
The c wave is a smaller peak than the a wave, and is due to bulging of the tricuspid valve into the right atrium during ventricular contraction. This takes place even though the chordae tendineae and the papillary muscles are holding the valve leaflets.
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