The renal medulla pyramids primarily contain which structures?

• A. Glomeruli
• B. Proximal tubules and collecting ducts
• C. Loops of Henle and Collecting Ducts
• D. Vasa recta

Answer: (C)

The medullary pyramids are built primarily from the tubules that extend through the medulla to concentrate urine. The loops of Henle reach down into the medulla from the cortex, creating the essential countercurrent mechanism, and the collecting ducts run through the medulla on their way to the papilla, gathering filtrate from many nephrons. Glomeruli sit in the cortex, not in the medullary pyramids, and proximal tubules are mainly cortical or outer medullary. The vasa recta are the capillary vessels that accompany these tubules in the medulla, but the tubules themselves are the main contents of the pyramids. So, loops of Henle and collecting ducts are the structures most associated with the medullary pyramids.