Page 1045 - Fundamentals of anatomy physiology

1032 Unit 5 Environmental Exchange Left ureter Rectum Figure 26–18 Organs for Conducting and Storing
Urine. ATLAS: Plates 62b; 64; 65
Peritoneum
The smooth muscle fibers of this sphincter provide in-
Urinary voluntary control over the discharge of urine from the
bladder bladder. The urinary bladder is innervated by postgan-
glionic fibers from ganglia in the hypogastric plexus
Pubic and by parasympathetic fibers from intramural ganglia
symphysis that are controlled by branches of the pelvic nerves.

Prostate Histology of the Urinary Bladder
gland
The wall of the urinary bladder contains mucosa,
External submucosa, and muscularis layers (Figure 26–19b).
urethral The muscularis layer consists of inner and outer lay-
sphincter ers of longitudinal smooth ­muscle, with a circular
Spongy layer between the two. Together, these layers form
urethra the powerful detrusor (de-TRU. -sor) muscle of the
urinary bladder. When this muscle contracts, it com-
External Urethra Urogenital presses the urinary bladder and expels urine into the
urethral [see part c] diaphragm urethra.

orifice a Male The Urethra

Rectum Vestibule Vagina The urethra extends from the neck of the urinary
Right ureter b Female bladder and transports urine to the exterior of the
body. The urethrae of males and females differ in
Uterus Center of trigone length and in function. In males, the urethra extends
Peritoneum Neck of from the neck of the urinary bladder to the tip of the
urinary bladder penis (Figure 26–18a,c). This distance may be 18–20 cm
Urinary Prostate gland (7–8 in.). We subdivide the male urethra into three
bladder Prostatic urethra segments: the prostatic urethra, the membranous
Membranous urethra urethra, and the spongy urethra. The prostatic urethra
Pubic c Urinary bladder in male passes through the center of the prostate gland. The
symphysis membranous urethra includes the short segment
that penetrates the urogenital diaphragm, the muscular
Internal floor of the pelvic cavity. The spongy urethra, or
urethral penile (PE. -nı.l) urethra, extends from the distal border
sphincter of the urogenital diaphragm to the external open-
Urethra ing, or external urethral orifice, at the tip of the
External penis. In females, the urethra is very short. It extends
urethral 3–5 cm (1–2 in.) from the bladder to the vestibule
sphincter (in (Figure 26–18b). The external urethral orifice is near
urogenital the anterior wall of the vagina.
diaphragm)
In both sexes, where the urethra passes through
26 Median umbilical the urogenital diaphragm, a circular band of skeletal
ligament muscle forms the external urethral sphincter. This
Ureter muscular band acts as a valve. The external urethral
sphincter is under voluntary control through the per-
Lateral ineal branch of the pudendal nerve. This sphincter
umbilical has a resting muscle tone and must be voluntarily
ligament relaxed to permit micturition.
Detrusor

muscle
Rugae

Ureteral
openings

Internal urethral
sphincter

External urethral
sphincter (in urogenital

diaphragm)