The invention relates to a bag system (1) for receiving and collecting a sample of a biological fluid or of one of the components thereof, comprising: - at least one main bag (2) for receiving the biological fluid or one of the components thereof, said main bag (2) being provided with at least one inlet orifice (25) and with an outlet orifice (26) for the fluid, - at least one secondary bag (21) for receiving the biological fluid or one of the components thereof, said bag (21) being in fluid communication with the main bag (2) by way of at least one other tube (28) connected to an orifice (27) of the secondary bag (21) and to one (26) of said orifices of the main bag (2), and - at least one sampling container (3) in fluid communication with said main bag (2) by way of a tube (5) connected to a second outlet orifice (7) of the main bag (2), so as to be able to receive a sample of the fluid contained in said bag, said sampling container (3) being provided with an access orifice (4) to the sample, and comprising an opening device (9) mounted in said orifice (4) of the container, said opening device (9) having a zone of weakness (10) designed to be able to be broken so as to permit access to the sample by way of the orifice (4) of said container.
