A syringe assembly (400) comprising: a fluid body (410) including a side wall having an inner surface defining a fluid chamber for retaining fluid and having a first width in cross section, an open proximal end and a distal end including a distal wall； a plunger rod (460) disposed within the fluid chamber (410) comprising a distal end, a proximal end, a plunger rod body extending from the distal end to the proximal end, and a stop disposed at the distal end of the plunger rod (460) to form a fluid tight seal with the interior surface of the body； a retraction body (420) disposed adjacent to the side wall of the fluid body (410), the retraction body including a wall having an inner surface defining a needle chamber, an open proximal end, an open distal end that includes a barrier wall, an opening between the wall of the retraction body (420) and the side wall of the fluid body (410) that allows fluid communication between the fluid chamber and the needle chamber and a cone assembly of the needle comprising a needle cone, a needle cannula attached to the needle cone, the needle cannula being in fluid communication with the opening and being pushed to move in a proximal direction； and a firing element (490) arranged inside the needle chamber and rotatable inside the retraction body (420) independently of the piston rod (460), characterized in that the firing element (490) includes a trigger guard (494) that prevents premature retraction of the needle cannula, the firing element (490) providing a firing force that causes the needle cannula to retract into the retraction body (420) , and the plunger rod (460) comprises a flat radial ring (462) that biases the trigger guard (494) so that the trigger element (490) can move in a distal direction to retract the needle cannula.Un conjunto (400) de jeringa que comprende: un cuerpo (410) para fluido que incluye una pared lateral que tiene una superficie interior que define una cámara para fluido para retener fluido y que tiene
