Author: Edwin Ocran, MBChB, MSc • Reviewer: Dimitrios Mytilinaios, MD, PhD Last reviewed: November 01, 2023 Reading time: 4 minutes
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Proximal convoluted tubule
Pars convoluta tubuli proximalis
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Synonyms:
Convoluted part of proximal tubule, Tubulus contortus proximalis
The proximal convoluted tubule (PCT) is the first tubular component of the nephron, the functional filtration unit of the kidney. It arises as a continuation of the flattened urinary (Bowman’s) space from the tubular pole of the renal corpuscle.
The proximal convoluted tubule is located within the renal cortex and as its name suggests, it is the most coiled section of the renal tubule. It measures about 14 mm in length and continues into the medulla as the loop of Henle. The proximal convoluted tubule is first to receive the ultrafiltrate from the urinary space of Bowman’s capsule and serves as the primary site for initial reabsorption.
Histologically, the proximal convoluted tubule is lined by simple cuboidal epithelium with a prominent brush border (tall microvilli) on its luminalsurface to enhance its reabsorption capacity. Additionally, these cells possess junctional complexes including tight junctions and zonula adherens, as well as extensive basolateral interdigitations that ensure cell-to-cell adhesion. Furthermore, these cells are rich in mitochondria which provide the energy, needed for its active transport processes and gives the cytoplasm a bright eosinophilic appearance on light microscopy.
The primary function of the proximal convoluted tubule is to actively reabsorb nearly all organic nutrients such as glucose, polypeptides and amino acids, electrolytes especially sodium (Na+), all plasma proteins, vitamins, and 60–65% of the water from the tubular fluid into blood in the peritubular capillaries. This is then transported into general circulation. Other organic anions and cations such as hydrogen (H+), and ammonium (NH4+) are in turn secreted into the filtrate.
Terminology English: Proximal convoluted tubuleSynonym: Convoluted part of proximal tubuleLatin: Pars convoluta tubuli proximalisSynonym: Tubulus contortus proximalis
Definition Initial coiled tubular component of the nephron arising from the tubular pole of the renal corpuscle Function Reabsorption of organic nutrients (glucose and amino acids), ions, vitamins, plasma proteins and water; secretion of anions and cationsLearn more about the nephron with the following study unit:
Learn faster Kidney: Cortex, medulla and pelvis Explore study unit Sources All content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our content quality guidelines. McKinley, M. & Loughlin, V. (2012). Human anatomy. New York: McGraw-Hill. Mescher, A. L., & Junqueira, L. C. (2013). Junqueira's basic histology: Text & atlas. McGraw-Hill Medical. Ross, M. H., & Pawlina, W. (2011). Histology : a text and atlas : with correlated cell and molecular biology (6th ed.). Wolters Kluwer/Lippincott Williams & Wilkins Health Young, B., O'Dowd, G., & Woodford, P. (2014). Wheater's functional histology: A text and colour atlas. Churchill Livingston/Elsevier. Standring, S. (2016). Gray's Anatomy (41st ed.). Edinburgh: Elsevier Churchill LivingstoneProximal convoluted tubule: want to learn more about it?
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