human
How does a syringe needle work?
assistant
A syringe needle is used to inject or withdraw fluids from a person. It has a hollow tube with a sharp point at one end and a plunger on the other end. The plunger is pushed down into the tube, which creates suction that draws fluid up through the tube. When the plunger is pulled back out of the tube, it creates negative pressure, which causes the fluid to be injected or withdrawn.