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How are renal pyramids arranged inside a kidney?

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Human kidneys — renal system Diagram showing the location of the kidneys in the abdominal cavity and their attachment to major arteries and veins.

Inside the human kidney, the renal pyramids are arranged within the renal medulla, which constitutes the inner substance of the organ. These triangular or cone-shaped masses of tissue are oriented with their bases facing outward toward the kidney's exterior and their apexes, known as the renal papilla, projecting inward toward the renal sinus.12

The cortex arches over the bases of these pyramids and fills the spaces between them. Between the pyramids, interlobar arteries are positioned to supply the tissue with blood. In humans, each kidney typically contains a dozen or more of these pyramids, which are organized into renal lobes alongside the overlying cortical tissue. The apexes of these pyramids project into minor calyxes, which collect urine produced by the kidney's tubules.21