= Minor calyx
A <minor calyx> is the cup-like first receiving passage around a <renal papilla>, collecting <urine> as it leaves the <collecting duct system>. It belongs to the <renal calyx> network; downstream convergence leads through a <major calyx> toward the <renal pelvis>. It should be distinguished from the papillary <tissue> projecting into its receiving space.<Kidneys by the National Cancer Institute>[internal anatomy: minor calyx surrounding a papillary outlet]{ref}
A longitudinal specimen makes the relationship clear. Follow aligned <collecting ducts> toward the tip of a <renal pyramid>, identify the <renal papilla>, and then identify the hollow collecting region around that tip. The tissue–space distinction is the same kind of anatomical distinction as separating a tube's wall from its <lumen (anatomy)>.<Longitudinal section through Kidney by the Manipal Museum of Anatomy and Pathology>[specimenEXC002: papilla and minor calyx]{ref}
An illustrative sampling comparison shows why this level matters. Fluid from a <minor calyx> has already pooled the output of many microscopic passages, but a sample taken farther downstream in the <renal pelvis> combines still more regions. Increasing the anatomical scale of collection can conceal differences that were present between individual <nephrons>.
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