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Renal Pyramids

Medically Reviewed by Anatomy Team

  • Last updated on January 28, 2025

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The renal pyramids are essential structural components of the kidney, playing a vital role in the organ’s ability to filter blood, regulate fluid balance, and excrete waste.[2] These pyramid-shaped structures are part of the kidney’s medulla and are key to its overall functionality.[1]

Structure

Renal pyramids are cone-shaped regions of the renal medulla, typically numbering 8 to 18 per kidney. Each pyramid has a broad base that faces the renal cortex and a pointed apex, known as the renal papilla, which projects into a minor calyx.

The pyramids are composed of:

  1. Straight Tubules and Collecting Ducts: These structures transport urine from the nephron to the renal pelvis.
  2. Loops of Henle: Located within the pyramids, they play a role in concentrating urine.
  3. Vasa Recta: A capillary network surrounding the nephron, critical for maintaining the kidney’s osmotic gradient.[4]

Location

Renal pyramids are located within the medullary region of the kidney, positioned between renal columns—extensions of the cortical tissue that separate adjacent pyramids.[3] The arrangement of pyramids and columns gives the kidney its characteristic lobular appearance.[6]

Function

  1. Urine Formation: The renal pyramids house nephron components such as loops of Henle and collecting ducts, which are responsible for filtering blood and forming urine.[8]
  2. Urine Transport: The collecting ducts converge at the renal papilla, where urine is emptied into the minor calyces and subsequently into the renal pelvis.[5]
  3. Maintenance of Osmotic Balance: The pyramids contribute to the kidney’s ability to create an osmotic gradient, critical for concentrating urine and regulating water balance.

Clinical Relevance

  • Medullary Sponge Kidney: A congenital disorder affecting the renal pyramids, leading to the formation of cysts within the collecting ducts.
  • Obstruction and Kidney Stones: Calculi can form in or near the renal papillae, causing pain and obstruction in the urinary tract.
  • Chronic Kidney Disease: Structural or functional damage to the renal pyramids can compromise the kidney’s filtration ability and lead to systemic issues.[7]
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References

  1. Ellison DH, Berl T. The Clinical Physiology of Water Metabolism and Renal Function. 2nd ed. Oxford: Oxford University Press; 2019. ISBN 978-0199332719.
  2. Testut L, Latarjet A. Traité d’Anatomie Humaine. 10th ed. Paris: Doin; 1948.
  3. Taal MW, Chertow GM, Marsden PA, et al. Brenner and Rector’s The Kidney. 11th ed. Philadelphia, PA: Elsevier; 2019. ISBN 978-0323532655.
  4. Weiss L, Greep RO. Histology. 5th ed. New York: McGraw-Hill; 1977. ISBN 978-0070690911.
  5. Fawcett DW. Bloom and Fawcett’s Concise Histology. 1st ed. London: Hodder Arnold; 2002. ISBN 978-0340806773.
  6. Lightwood R, Cumming R. Functional Anatomy of the Kidney. 2nd ed. London: Heinemann Medical; 1963. ISBN 978-0433164056.
  7. Kurata S, Tagawa H. Renal Structure and Function: An Integrated Approach. 1st ed. New York: Springer; 1988. ISBN 978-3540182323.
  8. Hricik DE, Sedor JR, Schulman GI. Pathophysiology of Renal Disease. 2nd ed. Baltimore, MD: Williams & Wilkins; 1995. ISBN 978-0683062208.