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Transitional Epithelium

Medically Reviewed by Anatomy Team

  • Last updated on January 27, 2025

Table of Contents

Transitional epithelium, also known as urothelium, is a specialized type of epithelium that can stretch and recoil without damage.[2] It consists of multiple layers of cells that change shape depending on the degree of distension in the organ it lines.

Anatomy

  • Structure:
    • In the relaxed state, the cells in the superficial layer appear dome-shaped (sometimes called “umbrella cells”).[3]
    • When stretched, the cells flatten, resembling squamous cells.
  • Cell Layers:
    • Basal layer: Cuboidal cells.
    • Intermediate layer: Columnar or polygonal cells.[4]
    • Apical layer: Dome-shaped cells that flatten during stretching.[5]

Location

Transitional epithelium is found exclusively in the urinary system, where organs need to accommodate varying volumes of liquid. Major locations include:

Function

  • Stretchability: Allows organs to expand and contract without tearing.
  • Barrier: Provides a protective lining, preventing the leakage of urine and protecting underlying tissues from its toxic components.[7]

Clinical significance

  • Urinary Tract Infections (UTIs): Recurrent infections can damage the transitional epithelium, leading to discomfort and potential complications.
  • Bladder Cancer: Transitional cell carcinoma arises from the transitional epithelium and is a common cancer affecting the bladder.[8]
  • Obstruction Effects: Chronic obstruction (e.g., kidney stones) can cause changes in the transitional epithelium, potentially leading to complications like hydronephrosis.[1]

References

  1. Kerr JB. Atlas of Functional Histology. 1st ed. Mosby; 2010. ISBN 978-0723435020.
  2. Young B, O’Dowd G, Woodford P. Wheater’s Functional Histology: A Text and Colour Atlas. 6th ed. Elsevier; 2013. ISBN 978-0702047473.
  3. Moini J. Functional and Clinical Histology for Medical Students. 1st ed. Academic Press; 2020. ISBN 978-0128174372.
  4. Singh I. Textbook of Human Histology with Colour Atlas and Practical Guide. 9th ed. Jaypee Brothers Medical Publishers; 2019. ISBN 978-9352705679.
  5. Mescher AL. Junqueira’s Basic Histology: Text and Atlas. 15th ed. McGraw-Hill Education; 2018. ISBN 978-1260026177.
  6. Stevens A, Lowe JS. Human Histology. 4th ed. Elsevier; 2015. ISBN 978-0723435020.
  7. Gartner LP, Hiatt JL. Textbook of Histology. 4th ed. Elsevier; 2021. ISBN 978-0323683715.
  8. Fawcett DW, Jensh RP. Bloom and Fawcett: Concise Histology. 2nd ed. Hodder Arnold; 2002. ISBN 978-0340806774.