I33: The Stairway to Heaven

The human spine when observed prone or supine looks similar to the letter I as if facing a stairway. Thirty-three vertebrae compose the human spine.

Further l + 3 + 3 = 7 Seven also represents the portals of entry within the human head.

The stairway of vertebrae along the spine when added (I + 3+ 3 = 7) leading to the head and again the seven gates.