Inside the heart the atrioventricular valves (AV) have chordae tendineae to prevent the backflow of blood into the atrium when the ventricle contracts.

Since the AV and semilunar valves are effectively the same thing but in different locations, it would make sense that the semilunar valves also need chords to prevent blood backflow. But they do not. Why doesn't blood flow back into the ventricle after the semilunar valve closes?

  • I think it's maybe related to coronary arteries orifice location and coronary arteries pressure.
    – mncam
    Jul 21 '20 at 10:08
  • Certainly a valid physiology question imo. What has your research so far yielded?
    – Thomas
    Jul 21 '20 at 14:24
  • You say they are "effectively the same thing" but have you looked at their structure? They are built entirely differently. Jul 21 '20 at 18:49

Unlike atrioventricular valves, semilunar valves' leaflets are concave, somewhat like shallow bags, which, during the diastole are filled with blood and therefore are pushed back to touch one another and so close the valve opening.

Here's a good gif to visualise.

Some reference: 4 Valves of the Heart: What Are They & How They Work

  • but when the blood pushes back on the semilunar valves what stops them from opening backwards?
    – John Hon
    Jul 22 '20 at 23:35

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