Final answer:
The hub of the needle fits into the syringe, ensuring a secure and leak-proof connection between the needle and the syringe barrel.
Step-by-step explanation:
The part of the needle that fits into the syringe is called the hub. The hub is typically made of plastic and is designed to connect securely to the tip of the syringe barrel, providing a leak-proof seal. This connection allows the liquid to be drawn into the barrel when the plunger is pulled back, and then pushed out through the needle when the plunger is pressed down.
In a typical hypodermic syringe, the diameters of the barrel and needle are tailored for specific uses, often measured in millimeters or gauge. It is essential for the hub to match the specific syringe design to ensure proper function and safety during the administration of liquids. For example, when discussing making connections with syringes or the dynamics of a fluid, such as the scenario of a needle-cork combination orienting itself in water, the hub's role in ensuring a tight fit becomes particularly relevant.