The anatomy of the syringe
1. Stopper: Prevents leakage of medication around the plunger, and acts as an indicator for measuring the syringe’s contents (see diagram).
2. Scale Markings: Scale markings are typically in milliliter (mL) units. On insulin syringes, however, graduations are displayed in “units” based on the insulin concentration prescribed. (Example: U-100 means 100 units of insulin suspended within 1 milliliter of fluid. A 3/10 mL insulin syringe will accommodate up to 30 units when using U-100 insulin.)
3. Barrel: Reservoir for holding liquid, clearly graduated to allow accurate and visual measurement of the syringe’s contents.
4. Flanges: The “wings” that extend out from the side of the syringe barrel that provide an area or surface for the index finger and middle finger to grasp during aspiration or administration.
5. Plunger Rod: A piston-like device inside the barrel.
6. Thumb Press: Area where clinician presses to push plunger rod down into barrel to expel contents.