Transitional Epithelium-Urothelium-Urinary Bladder

Transitional epithelium (urothelium) forms a superficial layer, which is spe-cific for the ureters – i.e., for the renal pelvis, ureters, urinary bladder and the initial part of the urethra. The unique characteristic of urothelium is its ability to adapt to volume changes and respond to the tensile forces in the lumen of the urothelium-lined organ. Dependent on the relaxed or distended state of the urinary bladder, urothelium changes its configuration, under-going a transition from a multilayered type to a type with ostensibly fewer layers (= transitional epithelium). In most instances, at least three layers are present. The layers are identified as the basal layer 1 , followed by the intermediary layer 2 and, spanning the intermediary cells like an umbrella, the superficial cells . The cells in the intermediate layer 2 , in particular, show irregular shapes, and they are separate d by wide intercellular spaces. Polyploid nuclei are characteristic of the superficial cells. There are also superficial cells with two nuclei. Underneath their apical plasmalemma, superficial cells of ten show a heavily stained area ( “crust”). The transitional epithelium has been described sometimes as epithelium with several rows, and sometimes as Pseudostratified epithelium.

1 Basal cells

2 Intermediary cells

3 Superficial cell (cells of the superficial layer)

4 Lamina propria

Stain: hematoxylin-eosin; magnification: × 400

References

Kuehnel, W.(2003). Color Atlas of Cytology, Histology, and Microscopic Anatomy. 4^th edition . Institute of Anatomy Universitätzu Luebeck Luebeck, Germany . Thieme Stuttgar t · New York .

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