Renal columns are defined as:

Renal columns are specialized structures found within the kidney that play a crucial role in the organization of the renal cortex and medulla. They are columns of cortical tissue that extend between the renal pyramids, which are the triangular structures located in the medulla of the kidney. This arrangement allows for the structural separation and organization necessary for the efficient functioning of nephrons, the functional units of the kidney.

The primary function of these columns is to support the pyramids and contain blood vessels, tubular structures, and connective tissue that are essential for renal function. By effectively separating the pyramids, renal columns help maintain the arrangement required for the proper flow of urine and facilitate the overall filtration processes that take place in the nephron.

Therefore, identifying renal columns as bundles of tissue extending between the pyramids from the cortex accurately describes their anatomical position and function within the kidney's structure.