Prostate Anatomy & Histology: Complete Guide for Clinicians

Gross anatomy – location, size, shape, capsule

The prostate is a fibromuscular glandular organ located in the male pelvis, inferior to the bladder and posterior to the pubic symphysis. It surrounds the prostatic urethra.

• Shape: Inverted cone or chestnut-shaped.
• Dimensions: Base: 3-4 cm (width) × 2-3 cm (height). Apex: 2-3 cm (width). Length (base to apex): 3-4 cm.
• Weight: 15-20 g in young adults; increases with age (BPH).
• Capsule: The prostate is surrounded by a fibromuscular capsule (false capsule) that condenses from the periprostatic fascia. This capsule is clinically important for surgical planes during radical prostatectomy.
• Relations:
  • Anterior: Pubic symphysis (retropubic space of Retzius)
  • Posterior: Rectum (separated by Denonvilliers' fascia)
  • Superior: Bladder neck
  • Inferior: Urogenital diaphragm and external urethral sphincter
  • Lateral: Levator ani muscles and neurovascular bundles

Zonal anatomy – peripheral, central, transitional zones

The zonal anatomy of the prostate, described by McNeal in 1968, is essential for understanding disease distribution.

• Peripheral zone (PZ) – 70% of glandular tissue:
  • Location: Posterior and lateral aspects of the prostate
  • Ducts empty into the distal prostatic urethra
  • Clinical importance: Site of 70-80% of prostate cancers
  • Palpable on digital rectal exam (DRE)
• Central zone (CZ) – 25% of glandular tissue:
  • Location: Base of the prostate, surrounding the ejaculatory ducts
  • Ducts empty near the verumontanum
  • Clinical importance: Uncommon site for cancer (5-10%)
• Transitional zone (TZ) – 5% of glandular tissue:
  • Location: Surrounds the proximal prostatic urethra
  • Clinical importance: Site of benign prostatic hyperplasia (BPH)
  • Rare site for cancer (10-15%), but cancers here are often palpable
• Anterior fibromuscular stroma (AFMS):
  • Location: Anterior surface of the prostate
  • Non-glandular tissue – smooth muscle and fibrous tissue
  • Clinical importance: Can be a site for anterior prostate cancer (5-10%)

Clinical significance of zones – BPH vs. cancer

Understanding zonal anatomy is critical for clinical practice:

• BPH (benign prostatic hyperplasia): Arises in the transitional zone and periurethral glands. This explains why BPH causes urinary obstruction (the TZ surrounds the urethra).
• Prostate cancer: 70-80% arise in the peripheral zone. This explains why many prostate cancers are palpable on DRE (the PZ is posterior, adjacent to the rectum).
• Anterior prostate cancer: 5-10% arise in the anterior fibromuscular stroma or anterior transitional zone. These are not palpable on DRE and may be missed on standard biopsy templates (requires anterior sampling or MRI-targeted biopsy).
• Transitional zone cancer: 10-15% arise in the TZ. These may be less aggressive and often have lower Gleason scores.

Histology – glandular epithelium and stroma

The prostate is a tubuloalveolar gland composed of epithelial and stromal components.

Epithelial cells:

• Basal cells: Thin layer of cuboidal cells at the base of the epithelium. Express high-molecular-weight cytokeratins (34βE12, CK5/6). Loss of basal cells is a hallmark of prostate cancer (used in immunohistochemistry).
• Secretory (luminal) cells: Tall columnar cells that produce prostatic fluid, including PSA (prostate-specific antigen) and PAP (prostatic acid phosphatase). Express androgen receptors.
• Neuroendocrine cells: Scattered cells that produce chromogranin A, serotonin, and calcitonin. Rarely form pure neuroendocrine tumours (small cell carcinoma of the prostate).

Stroma:

• Smooth muscle cells (contractile function)
• Fibroblasts
• Extracellular matrix (collagen, elastin)
• Blood vessels and nerves

Immunohistochemistry in diagnosis:

• Basal cell markers (positive in benign glands): 34βE12 (high-molecular-weight cytokeratin), p63, CK5/6
• Loss of basal cells: Suggests prostate cancer
• AMACR (racemase): Overexpressed in prostate cancer (positive in malignant glands)

Blood supply – arteries, veins, Batson's plexus

Arterial supply:

• Main supply: Inferior vesical artery (branch of the internal iliac artery)
• Prostatic arteries: Arise from the inferior vesical artery and enter the prostate at the posterolateral border
• Accessory supply: Middle rectal artery, internal pudendal artery (minor contributions)

Venous drainage:

• Prostatic venous plexus (Santorini's plexus): Surrounds the prostate and bladder neck
• Drains into: Internal iliac veins
• Batson's plexus (vertebral venous plexus): Communication between the prostatic venous plexus and the vertebral veins. This provides a route for prostate cancer metastasis to the spine without passing through the lungs.

Innervation – neurovascular bundles, sympathetic and parasympathetic

Parasympathetic (erectile function):

• Nerve origin: Pelvic splanchnic nerves (S2-S4)
• Path: Run posterolaterally to the prostate as the neurovascular bundles
• Function: Vasodilation → erection
• Surgical importance: Injury to neurovascular bundles during radical prostatectomy causes erectile dysfunction

Sympathetic (ejaculation):

• Nerve origin: Hypogastric nerves (T10-L2)
• Function: Smooth muscle contraction → ejaculation, bladder neck closure

Somatic:

• Pudendal nerve (S2-S4): Controls the external urethral sphincter and bulbospongiosus muscle

Lymphatic drainage – obturator, internal iliac, presacral nodes

Prostate cancer typically spreads first to regional lymph nodes before distant metastasis.

• Primary drainage: Obturator and internal iliac (hypogastric) lymph nodes
• Secondary drainage: External iliac, presacral, and common iliac nodes
• Lymph node dissection during radical prostatectomy: Obturator and internal iliac nodes are removed for staging

Embryology – development from urogenital sinus

The prostate develops from the urogenital sinus (endoderm) under the influence of androgens (testosterone, DHT).

• Week 10-12: Prostatic buds sprout from the urogenital sinus
• Second trimester: Glandular branching and differentiation
• Birth: Prostate is small and primarily stromal
• Puberty: Androgen surge causes rapid growth and glandular development

Age-related changes – growth patterns, BPH

The prostate grows throughout life, with two phases of growth:

• First growth phase (puberty): Prostate reaches adult size (15-20 g) by age 20-25
• Second growth phase (after age 40): Gradual enlargement due to BPH (transitional zone)
• Histological changes with age:
  • Increased stromal component
  • Glandular atrophy
  • Chronic inflammation (common)
  • Corpora amylacea (calcified proteinaceous deposits)

Interactive FAQ – Prostate anatomy and histology

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Disclaimer: This information is for educational purposes and intended for clinicians and medical students. It is not a substitute for clinical judgment or primary literature.