Ureters, Bladder, and Urethra
Urinary Passage (made of the ureters, urinary bladder, and urethra) are made of the following layers:
- Mucosa has:
- Transitional epithelium and lamina propria. No muscularis mucosa or submucosa
- Muscularis has:
- 2 layers of smooth muscle in tubular portions (ureters and urethra). The inner layer is loose spiral called longitudinal layer and the outer layer is tight spiral called the circular layer. This arrangement is opposite that of the muscularis externa of the intestinal tract
Ureters are made of thick muscular walls. The upper two thirds contain inner longitudinal and outer circular. In the lower third there is an additional outer longitudinal layer added. Peristaltic contraction of the smooth muscles squeeze the urine toward the urinary bladder.
Urinary Bladder is a muscular-walled sac. The three layers of smooth muscles of the wall are not very distinct. The mucosa is folded in an empty bladder. It is lined with transitional epithelium. The lamina propria contains a higher proportion of collagen and elastic fibers.
- Transitional epithelium is impermeable to salts and water. It has the ability to become thinner and flatter, and permits distension of lining of these passages. The structure of surface cells adapted to accommodate distension. Routinely, surface cells are rounded and bulge into lumen of passage. It is described as dome-shaped.
Male Urethra is the terminal part of urinary and genital systems. There are three distinct segments:
- Prostatic urethra is 3-4 cm from the neck of the bladder through prostate gland, lined with transitional epithelium
- Membranous urethra is 1 cm from the prostate through the body wall – transitional epithelium ends here. It is lined with a stratified or pseudostratified columnar epithelium
- Penile urethra is 15 cm through the length of penis to the body surface. It is lined with pseudostratified columnar except at end where it is lined with stratified squamous epithelium
To insert urethral catheter in males, you should be familiar with the following: the entire urethra is about 20 cm, it is curved, and its lining has many small diverticula (noticeable when a catheter of insufficient caliber is used).
Female urethra is 3-4cm long. The mucosa has longitudinal foles. The lining is transitional, which changes to stratified squamous epithelium at its end.