In a further preferred aspect of the present invention, the elongate penetrating element is {HEAD ~ a needle}, having {TAIL ~ a retractable obturator} at its distal end 
having
In a further preferred aspect of the present invention , the elongate penetrating element is { HEAD ~ a needle } , having { TAIL ~ a retractable obturator } at its distal end
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH