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Structure

Prostate

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The prostate is a walnut-sized accessory gland of the male reproductive tract that surrounds the proximal urethra. It contributes fluid to semen and is a frequent site of benign and malignant disease with ageing.

Terminologia Anatomica (Latin): Prostata · Open in the 3D atlas

Location

It lies in the lesser pelvis below the bladder neck, behind the pubic symphysis and in front of the rectal ampulla, so its posterior surface can be palpated on digital rectal examination. The base abuts the bladder and the apex rests on the urogenital diaphragm (external sphincter).

Structure

The prostate has a base, apex, anterior, posterior and two inferolateral surfaces and is traversed by the prostatic urethra and ejaculatory ducts. McNeal zones: peripheral zone (about 70 %, most carcinomas), central zone, transition zone (benign prostatic hyperplasia) and anterior fibromuscular stroma; the old lobe nomenclature is still used clinically. Figures are approximate.

Blood supply

Supply is mainly from the inferior vesical artery (a branch of the internal iliac), with contributions from the middle rectal and internal pudendal arteries. The prostatic venous plexus drains to the internal iliac veins and communicates with the vertebral venous plexus (Batson), a route for vertebral metastases. Lymph drains mainly to internal iliac and sacral nodes.

Innervation

Sympathetic (T10-L2, via the hypogastric plexus) fibres cause smooth muscle contraction during emission; parasympathetic fibres (S2-S4, pelvic splanchnic nerves) stimulate secretion. The cavernous nerves run along the posterolateral margin and are at risk in prostatectomy, with consequences for erectile function.

Function

It secretes a slightly acidic fluid rich in citrate, zinc, acid phosphatase and prostate-specific antigen (PSA), which forms about a third of the semen volume (approximate) and helps sperm motility and liquefaction. Smooth muscle contraction aids ejaculation and closes the bladder neck.

Clinical correlations

Benign prostatic hyperplasia (transition zone) causes lower urinary tract symptoms and retention; prostatitis and adenocarcinoma (usually peripheral zone, palpable as a hard irregular nodule) are common. PSA screening policy varies between countries and is an area of ongoing debate; follow local guidelines.

Common exam points

  • Zones: peripheral (most cancers), transition (BPH), central, anterior fibromuscular stroma.
  • Posterior surface palpable on digital rectal examination; median sulcus normally present.
  • Prostatic urethra contains the seminal colliculus with the ejaculatory ducts and the prostatic utricle.
  • Venous plexus communicates with the vertebral venous plexus (Batson).
  • Cavernous nerves lie posterolaterally and are at risk in prostatectomy.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Netter FH. Atlas of Human Anatomy. Elsevier — Tier 3 (textbook)

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