A renal calyx is a cup-like collecting passage within the kidney that receives urine leaving a renal papilla. A minor calyx lies around a papillary outlet; these passages join into a major calyx, which drains toward the renal pelvis and then the ureter. The calyx is therefore part of the outflow route, downstream of the collecting duct system, rather than a site where the glomerulus first filters blood.[ref]
Kidneys by the National Cancer Institute. internal anatomy: minor/major calyces and renal-pelvis drainage
The branching arrangement supplies a simple mass balance. Suppose three upstream minor calyx passages deliver steady volumetric flow rates of , and to one outlet. With no storage or side flow, that outlet carries . These illustrative values describe how branches combine; they are not normal human flow measurements.
A longitudinal anatomical section makes the distinction visible: locate the pointed renal papilla first, then the hollow receiving space around it. The projecting tissue and its receiving passage are adjacent structures with different roles.[ref]
Longitudinal section through Kidney by the Manipal Museum of Anatomy and Pathology. specimenEXC002: papilla, minor calyx, major calyx and pelvis
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