WORKSHOP IN HISTOLOGY, CYTOLOGY AND EMBRYOLOGY - 2016

Chapter 4. TISSUES

Slide 32. Transitional epithelium (urothelium) of the urinary bladder.

Staining: hematoxylin and eosin.

Magnification: x400.

At low magnification, the mucosa of the Urinary Bladder exhibits a folded relief. The epithelium is stretched over the crests of the folds and contracted within the crypts. Therefore, it should be examined in both states.

Within the depths of the selected fold at high magnification, 8 to 10 Cell layers can be distinguished. The basal layer (1) is formed by small Cells with rounded nuclei. This layer rests on the basement membrane, beneath which lies Connective Tissue (2). The Cells of the intermediate layer (3) are irregularly shaped and, interlocking with one another, form 6 to 8 rows. The superficial layer (4) includes cells whose shape resembles a cap or an umbrella—umbrella cells, which are frequently multinucleated.

At the crest of the fold, the epithelial thickness is nearly halved compared to its depths. The cells of the basal layer exhibit more intense staining. The cells of the intermediate layer become lower, forming fewer rows. The cells of the superficial layer flatten out.

A schematic diagram of the epithelium in its unstretched (A) and stretched (B) states is provided separately.

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Slide 32. Transitional epithelium (urothelium) of the urinary bladder.