Ultra-low waste disposable syringe with self-adjusting integrated safety features

A needle and syringe system, comprising:

• a syringe barrel having an interior;
• a plunger rod having a first end and an opposite second end, said plunger rod having a bore formed therein that is accessible from said first end, wherein said bore extends for a first length into the plunger rod from said first end, and wherein said plunger rod can be reciprocally moved within said syringe barrel between a first position and a second position;
• a needle extending through a central post of a needle base;
• a tubular spacer that defines a central conduit, wherein said central post of said needle base and said central conduit of said tubular spacer have an equal length, wherein said first end of said plunger rod is closest to said tubular spacer when in said first position within said syringe barrel and is further from said tubular spacer when in said second position within said syringe barrel;
• and
• a plug having a length at least as long as said first length of said bore, said plug being separate and distinct from both said plunger rod and said tubular spacer, wherein said plug is initially disposed within said central conduit of said tubular spacer and leaves said central conduit to transfer into said bore on said plunger rod as said plunger rod is moved between said first position and said second position for a first time, wherein said plug completely blocks said central conduit of said tubular spacer and isolates said needle from said interior of said syringe barrel when said plug is present within said central conduit of said tubular spacer and wherein said plug completely fills said bore when fully received within said bore.