All three tubules that are found in the medullary ray are also in the renal medulla. The only difference is that, by definition, the collecting tubules become collecting ducts in the renal pyramid. The boundary is the arcuate arteries that define the corticomedullary junction. In the medulla that is close to the cortex, ascending and descending thick limbs, thin limbs of Henle’s loop (HA8, T) and collecting ducts (HA8, C) are present.