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Components of a Syringe

A syringe uses suction and pressure to transport liquids to and from the body. The instrument has three parts: barrel, plunger and needle. If you are beginning home injections, have an injection training at your clinic. You should always use a sterile syringe to inject yourself.

  1. Barrel

    • The barrel is the largest part of the syringe. It holds the liquid medication. Barrels are as small as one millimeter (cc), and as large as 10 milliliters (cc). This part is made out of plastic with measurements on the side printed in black ink. Do not use the syringe if the volume lines are not readable due to reuse. The end opposite the needle has plastic finger holders that protrude from the sides of the barrel. This helps you grip the barrel with two forefingers, and the plunger with a thumb during injection.

    Plunger

    • The plunger is located inside the barrel, creating an air-tight seal with its rubber stopper. A small part remains exposed on the end opposite the needle to withdraw and depress fluids. The rubber end allows you to fill the barrel with liquid by creating a vacuum inside the syringe, forcing the liquid into the barrel. The seal ensures that all medication is fully depressed out of the syringe.

    Needle

    • Needles, made of stainless steel, are the only part of a syringe that penetrates into your body. They are as small as 30-gauge, and as large as 18-gauge. A gauge is the sizing scale for needles, with large numbers indicating a smaller needle diameter. Subcutaneous injections, just below the skin's surface, use smaller needles, both in gauge and in length. Vaccinations and insulin injections most commonly use subcutaneous needles. Deep intramuscular shots require mid-sized needles, for example, into the gluteus, pectorals or biceps. Withdrawing blood utilizes the largest needles, quickly taking the necessary tissue from the body. Needles have plastic caps that should remain on while not in use.

    Sterilization

    • All three parts of the syringe must be sterile and clean before use. Any instrument taken from a sealed, sterile package is ready to use. Hospitals and pharmacies carry new, sterile and sealed syringes for home injection medication. Insulin patients may also reuse syringes. If reusing a syringe, keep it capped at all times when not in use. Only let it touch the skin and top of medication bottle. Do not share you needle and avoid cleaning the tip with alcohol, as it rubs off the coating that helps the needle enter the skin. Consult your physician before reusing syringes.

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