The syringe consists of a syringe with a small hole in the front end and a matching piston rod. Syringes are used to inject small amounts of liquid or gas into or extract from areas inaccessible by other methods. When the core rod is pulled out, the liquid or gas is sucked in from the small hole in the front end of the needle barrel, and when the core rod is pushed in, the liquid or gas is squeezed out. The process of extracting or injecting gas or liquid with a syringe and needle is called injection
Needle injector
Syringes are often connected to subcutaneous needles to inject or extract liquids or gases into or from body tissue. They can also be used for injection through rubber membranes in medical devices, containers, or scientific instruments such as some chromatography methods. Injecting gas into a blood vessel can cause air embolism. The way to remove air from the syringe to avoid embolism is to invert the syringe and then squeeze out a little liquid before injecting it into the bloodstream.
The syringe can be made of plastic or glass, and usually has a scale indicating the volume of liquid in the syringe. Glass syringes can be sterilized with autoclaves, but because plastic syringes have a lower processing cost, most modern medical syringes are made of plastic, which further reduces the risk of blood borne diseases. Currently, needle cartridges for epidemic prevention injection and blood extraction are mostly made of plastic and are only used for one-time use. They can be discarded immediately after use to avoid cross infection of infectious diseases caused by reuse of needle cartridges.
In some situations where accuracy is not the primary concern for bacteria, such as quantitative chemical analysis, glass syringes are still used due to their small error and smooth movement of the push rod. The needle of a syringe is very small and thin.