Pelvic Cavity LO3
3. Review the portions of the urinary system that are associated with the pelvis.
Urine from the kidneys is conducted via the ureters to the urinary bladder. The ureters are tripartite. The parts of the ureter are:
- abdominal part: adjacent to psoas major m.; crosses anterior to genitofemoral n.; is crossed by gonadal vessels; and crosses over bifurcation of the common iliac a. into the external & internal iliac aa.; is retroperitoneal
- pelvic part: traverses the pelvic cavity retro- and then subperitoneally; notable structure that may be found superior to the ureter include: ductus (vas) deferens, uterine a.; transitions into the intramural part at the base of the urinary bladder
- intramural part: contained within the wall of the base of the urinary bladder.
The urinary bladder is a distensible, urine-storing, subperitoneal organ.
The apex of the urinary bladder is supero-posterior to the superior portion of the pubic symphysis. The apex is connected to the umbilicus by the median umbilical ligament, the peritoneal fold containing the urachus. Inferior from the apex is the anterior surface of the bladder, which lies adjacent to the pubic symphysis. Posterior to the apex is the superior surface of the bladder. The superior surface is covered by peritoneum. The base/fundus of the bladder is the posterior-most wall (opposite the apex). It may be closely associated with either the vagina (women), or the rectum (men). The wall of the base contains the intramural parts of the ureters, which open into the lumen of the bladder via ureteric orifices. The neck is the inferior-most portion of the bladder, and contains the internal urethral meatus. In males, the neck of the bladder is superiorly adjacent to the prostate gland, and in females, the neck is very closely associated with vagina. The neck is held in place anteriorly and anterolaterally by the pubovesical ligament (women) / puboprostatic ligament (men). The triangular space proscribed by the ureteric orifices and the internal urethral meatus is called the trigone.
The bladder is principally supplied by blood from the superior and inferior vesical aa., branches of the anterior division of the internal iliac a. The bladder is innervated by the (autonomic) vesical plexus, which receives fibers from the inferior hypogastric plexuses.
The urinary bladder voids urine to the external environment through the urethra. The urethra is substantially sexually polymorphic.
The typical female urethra begins at the internal urethral meatus, travels anteroinferiorly between the pubic symphysis and vagina, and terminates in the external urethral meatus. The external urethral meatus is typically found in the vestibule of the vagina between the glans clitoris and the opening of the vagina.
The typical male urethra is tripartite, its parts including:
- intramural (preprostatic) part: neck of bladder to prostate
- prostatic part: begins at the internal urethral meatus, traverses the prostate gland, where it receives secretions of the prostate as well as from the ejaculatory ducts (this is the point of entry of semen into the urethra)
- membranous part: traverses the pelvic diaphragm
- spongy/penile part: traverses the corpus spongiosum of the penis; ends in the external urethral meatus on the distal ventral portion of the glans penis.