= Renal column
A <renal column> is an inward extension of the <renal cortex> between neighboring <renal pyramids>. It is part of the <kidney>'s living <tissue>, continuous with the outer cortex, rather than an empty drainage passage. The <renal medulla> is organized into pyramids, with cortical tissue extending between them.<Kidneys by the National Cancer Institute>[internal anatomy: cortex, pyramids and renal columns]{ref}
A longitudinal section provides a useful identification exercise. First locate two adjacent <renal pyramids> by following their striations toward their <renal papilla> outlets. Then trace the intervening tissue outward into the <renal cortex>. That continuity identifies a <renal column>; the hollow receiving spaces beside the papillary tips belong instead to the <renal calyx> system.<Longitudinal section through Kidney by the Manipal Museum of Anatomy and Pathology>[specimenEXC002: columns between pyramids]{ref}
This distinction explains why location alone can mislead: tissue lying deep between two pyramids is not necessarily medulla. The term describes how cortical tissue is arranged in three dimensions. A section's apparently separate cortical islands may simply be different cuts through one connected anatomical region.
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