Hypodermic needles are medical devices used for various purposes, including injections, blood sampling, and intravenous administration of fluids or medication. Here are the key features of hypodermic needles:

1. Size and Gauge: Hypodermic needles come in different sizes and gauges. The size refers to the overall length of the needle, while the gauge refers to the diameter or thickness of the needle. Common sizes range from 0.5 inches to several inches, and gauges typically range from 7 to 33, with higher numbers indicating thinner needles.
2. Needle Hub: The hub is the base of the needle that attaches to a syringe or other devices. It provides stability and allows for secure attachment. The hub can be made of various materials such as plastic or metal, and it may include features like luer locks or screw threads for secure connections.
3. Bevel and Tip Design: The bevel is the slanted or angled part at the tip of the needle. It allows for smooth entry into the skin or vessel. Bevel designs can vary, including regular bevel, short bevel, and long bevel, each with specific applications and advantages.
4. Cannula: The cannula is the hollow tube of the needle that carries fluids or medications. It is typically made of stainless steel or other metals, and its length can vary depending on the intended use. The cannula may have a thin-wall design to minimize trauma or a thicker wall for more robust applications.
5. Lumen: The lumen refers to the inner diameter of the needle, which determines the flow rate and the type of fluids or medications that can pass through it. Larger lumens allow for faster administration of fluids, while smaller lumens are suitable for delicate procedures or medications with higher viscosity.
6. Needle Point Types: Different needle point designs are available to suit specific applications. Some common types include:
   • Regular Point: A sharp, tapered point used for general injections and blood sampling.
   • Blunt Point: A rounded tip used for procedures where avoiding tissue damage is important, such as spinal injections.
   • Conical Point: A beveled, conical tip used for precise and controlled injections, such as epidurals or intramuscular injections.
   • Safety Point: A retractable or shielded needle tip designed to minimize accidental needlestick injuries after use.
7. Sterility: Hypodermic needles are typically sterilized to prevent infections. They are individually sealed in sterile packaging to maintain their integrity and prevent contamination.