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Ureter
The tunics of the ureters, urinary bladder, and urethra are specialized to accommodate changes in urine volume and to actively move urine through the urinary tract.
Ureter Cross Section
The mucosa surrounds the lumen; the mucosa comprises a layer of lamina propria and an innermost layer of transitional epithelium.
Transitional epithelium lines the ureters, urinary bladder, and the proximal urethra; this specialized epithelium comprises cells that change shape to accommodate changes in urine volume.
Transitional epithelium comprises stratified layers of cells that, when relaxed, are cuboidal. Umbrella cells within the transitional epithelium can flatten to expand and accommodate changes in urine volume. Note that these cells are often binucleated, which helps us to identify them under the microscope.
Superficial to the mucosa, we have two layers of muscularis: an inner longitudinal and outer circular layer. The distal ureter has a third outer longitudinal muscularis layer.
Lastly, adventitia comprises the outside of the ureter.