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I. Basic Principles: Prostate Anatomy

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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.