Why does knife slash at the External jugular vein cause air to be sucked in, forming an air emboli, instead of blood to rush out?

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Shouldn’t the air follow gravity and rush out of the vein? Why does air get sucked in instead?

In: Biology
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It’s a big blood vessel close to the heart. As it beats its pulling blood from the veins as well as pushing it into the arteries.

Also because veins have valves. Whatever blood is in that section will gush out, but the valves prevent excessive amounts from coming out.

the external jugular is a decent sized vein, but not really big enough for this to happen. It would just collapse. You’re probably thinking of the internal jugular vein, which is much larger. Veins have flimsy walls, and are low pressure. They can even have negative pressure as the heart expands. This could allow air to get in if the internal jugular was cut. However, even if that did happen, it would probably not be a significant amount of air before the high blood flow would fill the wound and prevent more air from going in