A needle is a long, slender, cylindrically shaped object with a sharp point on one end that is used for procedures that necessitate some sort of puncturing aspect.
They come pre-sterilized for your convenience, so they are ready to use straight out of the packaging!
They are fairly straightforward to use and require minimal explanation or instruction to properly handle
Their sharp tips and smooth surfaces reduce the chance of infection
They serve two purposes; to inject or extract liquids in and from the body
Hypodermic: Hypodermic needles are hollow, typically used in conjunction with a syringe to either inject substances, usually liquid, into the body or extract fluids, such as blood, from within it. Hypodermic needles are generally used when the substance being injected is not indigestible, because it wouldn’t absorb well (which holds true with insulin) or it runs the risk of damaging one’s liver. Another reason to use a hypodermic needle would be for the rapid administration of liquids. Hypodermic needles play an important role in reducing contamination for two reasons: its stainless steel surface is extremely smooth, which stops anything microscopic from getting caught in the irregularities of its surface. Ordinarily, those would then get pushed into human body when the needle served its purpose of puncturing the skin, but the smoothness of the surface protects the patient. Secondly the point of the needle is very sharp, which serves to dramatically shrink the size of the puncture hole. This prevents a lot of microbes from contaminating the wound and reduces the chance of infection.
Spinal: This kind of needle is typically much longer and thicker than your average needle and is used to inject fluids directly into the spinal cord.