As for the detention needle assembly body (1), ahead the sharp needle (41) while possessing, the needle (4) and the inside needle while (4) is locked to the basic end, the needle hub (5) and the inside needle (4) the outside needle of the air which passes (2) and the outside needle (2) to be locked by the basic end in the point, the tube (7) the terminal area which is connected (34) outside it possesses the needle hub (3) and the outside needle hub (3) be provided in the internal space, the inside needle (4) the possible hole (81) the seal component which it possesses (8) to have with the seal expedient which it possesses, the organism surfaceThe stab doing, it is something which is used. This detention needle assembly body (1) the seal component (8), it possesses water swelling property, it consists the swelling material where the swelling ratio is 2 - 50 times, the seal component (8) swelling does the seal component (8) from removal leaving it does the inside needle (4) the occasion where, the needle inside the said the seal component (8) by contacting in the body fluids which come in contact with (4), expands, the hole (81) blocks.留置針組立体(1)は、先端に鋭利な針先(41)を有する内針(4)と、内針(4)の基端部に固定された内針ハブ(5)と、内針(4)が挿通される中空の外針(2)と、外針(2)の基端部に固定され、チューブ(7)が接続される接続部(34)を有する外針ハブ(3)と、外針ハブ(3)の内部空間に設けられ、内針(4)を挿通可能な孔(81)を有するシール部材(8)を有するシール手段とを備え、生体表面に穿刺して用いられるものである。この留置針組立体(1)のシール部材(8)は、水膨潤性を有し、その膨潤率が2~50倍である膨潤性材料で構成され、シール部材(8)から内針(4)を抜去した際に、該内針(4)に付着した体液にシール部材(8)が接触することにより、シール部材(8)が膨潤し膨張して、孔(81)が閉塞する。
