How does a vacutainer (used for drawing blood) work?
Answers: Vacutainer(R) Needle
The Vacutainer needle have a sharp point at both ends, and usually is covered by a rubber sheath, with one expiration being shorter than the other. The long conclusion of the needle is used for sharp the vein, the shorter back is used to pierce the rubber stopper of the vacuum tube. The sheath makes it possible to draw several tubes of blood by preventing escape of blood as tubes are changed, this is called a multi-draw. If the short ruin is not covered with a rubber sheath, it is a single taste needle and single one tube of blood can be collected.
AS the name imply, there is a vacuum within the collection tube. When the sheathed proximal needle pierces the color-coded rubber stopper, blood is sucked into the tube. That assumes that the distal ending of the needle have successfully pierced the vein.
These tubes are relatively expensive in this day and age, so I can't suggest you waste one, but if you pierced the stopper next to a needle you would hear a swoosh.
When they are person produced at the factory they put a small amount of nutrient agar in the tube and autoclave the tube. The agar also contains an anticoagulant.
Once the rubber stopper is hermetically sealed while the tube is still hot, as it cools down it forms a natural vacuum.
When the stopper is pierced next to the needle it draws the blood up into the tube because of the vacuum formed when it cooled.
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