Urinary system: Ureter

The ureter (one per kidney) is a long, straight, muscle-walled tube. The epithelium lining this tube is stratified, transitional epithelium.

  • A thick, fibroelastic, lamina propria lies underneath the epithelium.
  • This mucosa (epithelium and lamina propria) is protective.
  • There are no mucosal or submucosal glands, and no submucosa.
  • There is a layer of smooth muscle outside the mucosa:
    • The upper two-thirds has two layers of smooth muscle: inner longitudinally arranged, and outer circularly arranged.
    • The lower third has three layers of smooth muscle; Inner longitudinal, middle circular, outer longitudinal.
  • Urine is squeezed into the bladder by peristalsis.
  • Outer adventitial layer has fibroelastic connective tissue, with blood vessels, lymphatics and nerves.
  • Folds of mucosa help to protect against reflux of urine when the bladder is full.