THE PELVIS
Fig. 6.13 Retrograde urethrogram in the male: oblique view.
1. Balloon of catheter in navicular fossa 2. Penile urethra 3. Bulbous urethra 4. Membranous urethra 5. Impression of verumontanum in prostatic urethra 6. Filling of utricle (not usually seen) 7. Air bubbles in contrast
The female urethra
• A posterior wall related to the rectum behind; and • Two inferolateral walls related to the muscles of the pelvic side wall and the anterior part of levator ani on either side. The urethra enters the upper part of the prostate near its anterior surface and then assumes a somewhat more central position before curving slightly anteriorly again to exit at the apex of the gland. Posterosuperiorly are the seminal vesicles. Fascia known as Denonvillier's fascia separates the prostate and seminal vesicles from the rectum. The puboprostatic ligament runs from the anterior inferior part of the gland to the pubic bone and provides support. The prostate gland has a fibrous (true) capsule and is further surrounded by a fibrous sheath derived from pelvic fascia and continuous with the puboprostatic ligaments. The prostatic venous plexus lies between the true capsule and the fibrous sheath. The prostatic capsule is thin and is frequently deficient posteriorly. According to traditional anatomy, the gland is described as having the following lobes which are not well demarcated from one another: • A muscular anterior lobe (or isthmus) which is anterior to the urethra and is composed mainly of fibromuscular fibres and contains little if any glandular tissue; • A posterior lobe which is posterior to the urethra and inferior to the insertion of the ejaculatory ducts; • A median lobe between the urethra and the ejaculatory ducts; and • Two lateral lobes, which form the bulk of the gland.
This is 4 cm long. It extends from the internal urethral sphincter at the bladder neck through the urogenital diaphragm to the external urethral meatus anterior to the vaginal opening. It curves obliquely downward and anteriorly. Multiple tiny urethral glands (of Skene) open into the urethra at the external meatus. The external urethral sphincter is at the urogenital diaphragm but is less well developed than that in the male. The involuntary internal urethral sphincter at the bladder neck appears to be more important in females.
Zonal anatomy of the prostate (Fig. 6.14)
THE MALE REPRODUCTIVE ORGANS (see Figs 6.7, 6.12-6.18)
The gland may more usefully be described based on its internal architecture as having three glandular zones with the non-glandular isthmus anteriorly:
The five lobes can only be differentiated in the fetus up to 20 weeks' gestation; in the mature gland only three lobes two lateral and one median - can be distinguished, with the fibromuscular stroma anteriorly. These lobes may be palpated through the rectum.
This gland is shaped like an upside-down truncated cone and surrounds the base of the bladder and the proximal (prostatic) urethra, extending inferiorly to the urogenital diaphragm and external sphincter. It has:
• The peripheral zone, which contains about 70% glandular tissue; • The central zone, which contains 25% glandular tissue; and • The transition zone, which contains 5% glandular tissue in the normal prostate.
• A base related to the bladder above; • An apex inferiorly sitting on the pelvic (urogenital) diaphragm; • An anterior wall which is separated from the pubic symphysis by the retropubic fatty space (of Retzius);
The central zone surrounds the urethra above the level of the ejaculatory ducts which pass through it, and roughly corresponds to the median lobe. The transition zone is a narrow area surrounding the urethra inside the central zone at the level of the ejaculatory ducts and
The prostate gland (Fig. 6.14)
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