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PELVIC STRUCTURES


PELVIC STRUCTURES
The relationships of male pelvic structures are illustrated in these complementary sagittal views—a para- median and a median section. In the lower median view, the complete course of the urethra from the bladder to the meatus at the end of the penis, its passage through the prostate gland and the urogenital diaphragm, is shown. In the upper paramedian view, part of the pelvic bones (os ilium and ischium) have been removed, but both rami of the left os pubis and part of the inferior ramus of the ischium are present. The soft parts are sectioned laterally from the midline. 

This view permits visualization of the course of the vas deferens as it originates in the scrotum and ascends to pass over the superior ramus of the pubis and ultimately to the posterior surface of the bladder, passing over the ureter on each side (“water under the bridge”). Note too that the bladder, as a hollow smooth muscular organ, has muscle fibers that run in all directions, like a ball of yarn, to enable uniform concentric contractions during micturition. The paramedian view also illustrates the fact that all male urogenital organs exist in the extraabdominal, retroperitoneal space and are covered by the peritoneum superiorly. Both views outline the attachments and course of the ischiocavernosus and bulbocavernosus muscles and demonstrate the suspensory and fundiform ligaments.

Anatomic details of external and internal organs will be discussed elsewhere (see pages 23, 24, 31, 51, 52, 76, and 77). However, well visualized here are the prostate gland below the bladder and paired seminal vesicles posterior to the bladder. The preperitoneal space of Retzius exists between the anterior surface of the prostate and bladder and the posterior surfaces of the symphysis and recti muscles. This retroperitoneally located potential space contains veins, areolar tissue, nerves, and lymphatics and is bounded below by the superior surface of the urogenital diaphragm. The posterior surfaces of the prostate and the seminal vesicles are separated from the anterior rectal wall by a definite, fibrous layer of fascia termed the rectovesical or Denonvilliers fascia that covers the entire posterior surface of the prostate from its apex, over the surface of the seminal vesicles superiorly to the rectovesical pouch. Denonvilliers fascia is an important surgical landmark for operations that involve removal of the prostate or reflection of the rectal wall from the surface of the prostate.
The fascial planes of the urogenital region have considerable clinical significance because of their important function in supporting anatomic structures, their identification as surgical landmarks, and because their layered arrangement forms several interfascial spaces that control the spread of exudates, malignancies, blood, or extravasated urine. In the plates that follow, these fascial layers will be shown in greater detail.