A syringe assembly (100, 200, 300) comprising: a fluid cylinder (110, 210, 310) that includes a side wall (112, 212, 312) having an inner surface (114, 214, 314) that defines a fluid chamber (115, 215, 315) for retaining fluid and having a first width in cross section, an open proximal end (119, 219, 319) and a distal end (111, 211, 311) that includes a distal wall (117, 217, 317)； a piston rod (160, 260, 360) disposed within the fluid chamber comprising a distal end, a proximal end, a piston rod body (163, 263, 363) extending from the distal end to the end proximal, and a plug (170, 270, 370) disposed at the distal end of the piston rod to form a fluid tight seal with the inner surface of the cylinder； a retraction cylinder (120, 220, 320) disposed adjacent to the side wall of the fluid cylinder, the retraction cylinder includes a wall (122, 222) having an inner surface (124, 224, 324) defining a chamber (125, 225, 325) needle, an open proximal end (219, 319), an open distal end (221, 321) that includes a barrier wall (127, 227, 327), an opening (118, 128, 218, 228, 318, 328) between the wall of the fluid cylinder and the side wall of the fluid cylinder such that the fluid chamber and the needle chamber are in fluid communication and a set (140, 240, 340 ) of a needle connection cone comprising a needle connection cone (142, 242, 342), a needle cannula (150, 250, 350) connected to the needle connection cone in fluid communication with the opening, the Needle cone cone assembly is predisposed to move proximally； and a trigger element (190, 290) characterized in that the trigger element is movable with the piston rod and extends into the needle chamber of the retraction cylinder, the trigger element provides a trigger force that causes the needle cannula retract into the retraction cylinder.Un conjunto de jeringa (100, 200, 300) que comprende: un cilindro (110, 210, 310) de fluido que incluye una pared lateral (112, 212, 312) que tiene una superficie interior (114, 2
