What is "renal pelvis"?

The renal pelvis is an expanded part of the kidney's collecting system, serving as a reservoir for urine before it flows into the ureter. It is located at the center of the kidney and receives urine from the renal calyces, which are small cup-like structures that collect urine from the kidney's filtration units called nephrons. The renal pelvis acts as a conduit, facilitating the smooth flow of urine from the kidneys to the ureter, ultimately leading to its elimination from the body.