Here is a schematic illustration of the interrelationships between the prostate, bladder, vas deferens, ureter, seminal vesicles, and rectum.
The dorsal vein leaves the penis under Buck’s fascia and penetrates the urogenital diaphragm dividing into 3 major branches - the superficial branch and the right and left lateral plexus. The superficial branch is the centrally located vein overlying the prostate and bladder neck. It is easily visualized early in retropubic operations and has communicating branches over the bladder and often into the pelvic sidewall. The lateral venous plexus travel posterolaterally toward the bladder neck and then communicate freely with the obturator and vesical plexus.
The pelvic plexus provides the autonomic innervation to the pelvic organs and external genitalia.
It is formed by parasympathetic fibers arising from S2-S4 and sympathetic fibers from the thoraco-lumbar center which travel through the hypogastric nerve. The pelvic plexus is located on the lateral side of the rectum 5 to 11 cm from the anal merge, with its mid-point located at the level of the tip of the seminal vesicle. The pelvic plexus provides branches that innervate the bladder, ureter, seminal vesicles, prostate, and rectum and the cavernous nerves that innervate the corpora cavernosa. The nerves that innervate the prostate travel outside the capsule of the prostate and Denonvilliers’ fascia until they perforate the capsule where they enter the prostate. The branches to the membranous urethra and corpora cavernosa also travel outside the prostatic capsule in the lateral pelvic fascia posterolaterally between the prostate and rectum.
The prostate receives arterial blood supply from the inferior vesical artery. After providing small branches to the seminal vesicle and base of the bladder the artery terminates in two large groups of prostatic vessels. The vessels that enter the prostate at its junction with the bladder supply the vesical neck and periurethral portion of the gland. These are the 5 and 7 o’clock arterial vessels that are frequently encountered during transurethral resection of the prostate. The capsular branches run along the pelvic sidewall in the lateral pelvic fascia posterolateral to the prostate providing branches that supply the outer portion of the prostate. These capsular vessels, including arteries and veins, provide a scaffolding for the cavernous nerves and form the neurovascular bundle which is the macroscopic landmark that aids in identification of the microscopic cavernous nerves.
The striated sphincter, which is responsible for passive urinary control, contains fatigue - resistant, slow twitch fibers. At the apex of the prostate the striated sphincter forms a tubular structure that surrounds the membranous urethra and apex of the prostate. Because the tributaries of the dorsal vein travel through the striated sphincter, great care must be taken when dividing the dorsal vein complex to avoid injury to the striated sphincter which is responsible for passive urinary control.
The prostate is covered with 3 distinct and separate fascial layers: the prostatic fascia, the levator fascia, and Denonvilliers’ fascia.. The prostatic fascia is in direct continuity with the true capsule of the prostate anteriorly and anterolaterally. The major tributaries of the dorsal vein travel within the prostatic fascia. The levator fascia is more superficial, adjacent to the pelvic musculature. It is important to recognize that the prostate receives its blood supply and autonomic innervation between the layers of the levator fascia and prostatic fascia. Denonvilliers’ fascia is a filmy delicate layer of connective tissue that is located between the anterior wall of the rectum and prostate. It is not seen on this illustration.
This demonstrates the way in which the dorsal vein complex divides into a superficial branch which travels anteriorly over the prostate and deeper branches that travel within the prostatic fascia. Note that the neurovascular bundle is between the layers of the prostatic and levator fascia.
Here is a cross section of the anatomy at the level of the urethra.
Distal to the apex of the prostate one can see the levator facia draped over the circumferential striated urethral sphincter which surrounds the smooth muscle of the urethra. Note the location of the neurovascular bundles outside the striated sphincter.
Next a cross section closer to the bladder neck.
Again note the levator fascia draped over the prostate adjacent to the levator musculature as it travels posterolaterally separating from the prostate to travel immediately adjacent to the pelvic musculature surrounding the rectum. The prostatic fascia surrounds the prostate. Denonvilliers’ fascia is located posteriorly. Note that the neurovascular bundle is in the space between the levator fascia and prostatic fascia. When nerve-sparing is performed correctly the prostatic fascia must remain on the prostate.