I. Basic Principles: Prostate Anatomy

ANATOMY OF THE PROSTATE

Detailed understanding of prostatic anatomy is essential for every urologist.

Figure 1: Prostate Anatomy
PS=pubic symphisis AFS=anterior fibromuscular stroma SV=seminal vesicle CZ, TZ, PZ=zones of prostate (see text)

• In a young adult, prostate weights ~20g and measures ~3 by 4 by 2 cm
• Apex = inferior portion of prostate, continuous with striated sphincter. Base = superior portion and continuous with bladder neck.
• Prostatic urethra
  • Covered by transitional epithelium
  • Hugs anterior portion of gland
  • Makes a ~30 degree bend in its mid portion (degree of angulation can vary from 0 to 90 degrees)
  • Verumontanum
    • just distal to urethral angulation
    • ejaculatory ducts (union of seminal vesicles and each vas deferens) drain to each side of prostatic utricle (vestigial Mullerian duct structure)
• Zones of Prostate (Figure 1)
  • Central zone (CZ)
    • Cone shaped region that surround the ejaculatory ducts (extends from bladder base to the veru)
    • Likely stems from Wolffian ducts
    • 25% of glandular tissue in young adults
    • Only 1-5% of prostate cancer from this region (likely because of Wolffian duct embryologic origin)
  • Peripheral zone (PZ)
    • Posteriolateral prostate
    • Mesodermal in origin
    • Majority of prostatic glandular tissue
    • Origin of up to 70% of prostate adenocarcinoma
  • Transitional zone (TZ)
    • Surrounds the prostatic urethra proximal to the veru (aka preprostatic urethra)
    • Endodermal in origin
    • In young men, accounts for only 5-10% of prostatic glandular tissue.
    • Only ~20% of prostate cancer arise from TZ
    • Gives rise to BPH
• "Lobes" of the prostate
  • Enlargement of periuthral tissue in the TZ results in hyperplasia of "lateral lobes" (Figure 2).
  • In some men, hyperplasia of periurethral glands of the TZ at the bladder neck produces a "median lobe" -- tissue mass that can ball-valve into the outlet (Figure 3)

Figure 2: Cystoscopic view of lateral lobes.
Edge of the verumontanum is seen at 6 o'clock.

Figure 3: Cystoscopic view of a large median lobe.
The ball-valve obstruction created by a median lobe in some men is clearly appreciated from this image.