Page 1046 - Fundamentals of anatomy physiology

Chapter 26 The Urinary System 1033

Figure 26–19 The Histology of the Ureter, Urinary Bladder, and Urethra.

Transitional Mucosa
epithelium

Lamina
propria

Smooth
muscle

Outer connective
tissue layer

Ureter LM × 65

a A transverse section through the ureter.

Transitional

epithelium Mucosa
Lamina

propria

Lumen of Submucosa
urethra
Detrusor muscle
Smooth
muscle

Female urethra LM × 50 Stratified Urinary bladder Visceral
squamous b The wall of the urinary bladder. peritoneum
epithelium
of mucosa LM × 36

Lamina propria
containing
mucous
epithelial glands

c A transverse section through the female
urethra. A thick layer of smooth muscle
surrounds the lumen.

&T i p s T r i c k s 26
To remember that the urethra is the urinary tract’s pipeline to
the exterior, proclaim, “Eureka! Your urine! It’s coming out the into the lamina propria. Connective tissues of the lamina
urethra!” propria anchor the urethra to surrounding structures. In fe-
males, the lamina propria contains an extensive network of
Histology of the Urethra veins. Concentric layers of smooth muscle surround the en-
tire complex.
The urethral lining consists of a stratified epithelium that
varies from transitional epithelium at the neck of the urinary The Micturition Reflex and Urination
bladder, to stratified columnar epithelium at the midpoint,
to stratified squamous epithelium near the external urethral As we have seen, urine reaches the urinary bladder by peristaltic
orifice. The lamina propria is thick and elastic. The mucosa contractions of the ureters. The micturition reflex coordinates
is folded into longitudinal creases (Figure 26–19c). Mucin- the process of urination (Figure 26–20).
secreting cells are located in the epithelial pockets. In males,
the epithelial mucous glands may form tubules that extend As the bladder fills with urine, stretch receptors in the blad-
der wall are stimulated. Afferent fibers in the pelvic nerves carry
impulses to the sacral spinal cord. The increased level of activity
in the fibers (1) facilitates parasympathetic motor neurons in