Peter Attia· MD
the sacrum is a is basically a single bone it's actually fused so it it at one point it was multiple bones right so so you have this sort of one fused sacrum and then you have these five lumbar discs numbered one through five now between each of those lumbar um vertebral bodies is a disc um and then there's one between the fifth lumbar vertebral body in the uh sacrum so uh we refer to them as you know l3 l4 is the disc between three and four and l5 s1 is the disc between there