Wondering if I need to bleed all the brake lines or just the one. Here's my situation.

One of my brake lines was severed and the car has been sitting for a while and all the fluid from the reservoir has leaked out. I have just recently replaced the line but have not yet had a chance to bleed it. I'm wondering if I need to bleed all the brakes or does the fluid remain isolated in each line?

 

if the reservoir leaked out, I would bleed all of them to be on the safe side.