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.