Venous access allows physician to deliver medicine directly into the bloodstream without repeatedly puncturing the blood vessels. In venous access, a long, thin tube, called a catheter, acts as a kind of entry way into vein. One end of the catheter is placed in a vein, usually in arm, neck, or chest. The other end exits body so that physician can deliver medicine into vein by means of the catheter. Sometimes this delivery end may be connected to a circular device called a port under the surface of skin.
Physicians often use needles to inject medicine into bloodstream. This way, the medicine is carried by bloodstream and quickly reaches the areas where body needs it. However, with repeated punctures, the needles can damage veins over time. If we have weak or thin veins, may not be able to receive many needle injections. Strong medicines can also scar veins.