Prostate Anatomy and Function

The prostate is a fibromuscular and glandular organ that surrounds the proximal urethra below the bladder and contributes a substantial fraction of seminal fluid. This topic covers its zonal anatomy and its secretory and muscular functions during ejaculation.

Definition

The prostate is an accessory sex gland that encircles the prostatic urethra and secretes a slightly acidic, enzyme-rich fluid—containing prostate-specific antigen, citrate, zinc, and acid phosphatase—that forms part of semen and participates in its coagulation and liquefaction.

Scope

The entry covers the gross position and relations of the prostate, McNeal's zonal model (peripheral, central, and transition zones, the anterior fibromuscular stroma, and preprostatic region), the histology of prostatic glands, and the composition and role of prostatic secretions in semen. It is a reference description of normal anatomy and function and does not address prostate disease management.

Core questions

• Where is the prostate located and what structures does it relate to?
• What are the zones of the prostate in McNeal's model and how do they differ?
• What does prostatic fluid contribute to semen?
• How does the prostate participate in emission and ejaculation?

Key concepts

• Peripheral zone
• Central zone
• Transition zone
• Anterior fibromuscular stroma
• Prostatic urethra and verumontanum
• Prostate-specific antigen and prostatic secretion
• Semen coagulation and liquefaction

Mechanisms

The prostate surrounds the prostatic urethra, into which the ejaculatory ducts open at the verumontanum. In McNeal's zonal model the gland is divided into the peripheral zone (the largest glandular region), the central zone surrounding the ejaculatory ducts, the transition zone flanking the proximal urethra, the preprostatic sphincteric region, and the non-glandular anterior fibromuscular stroma. Prostatic glandular epithelium secretes fluid rich in prostate-specific antigen, citrate, zinc, and acid phosphatase; this contributes a portion of the ejaculate, and prostate-specific antigen helps liquefy the semen coagulum formed by seminal-vesicle proteins. During emission, contraction of the prostatic smooth muscle expels secretions into the urethra.

Clinical relevance

The zonal anatomy of the prostate is fundamental to imaging interpretation, biopsy planning, and pelvic surgery, and prostatic secretions are relevant to semen analysis. This entry describes normal anatomy and function for educational orientation and is not a basis for diagnosing or treating prostatic disease.

Evidence & guidelines

The zonal description follows McNeal's anatomical studies, and the account of prostatic secretion draws on classic biochemical work on human semen and on standard anatomical references. As a normal-anatomy topic it is not governed by disease-specific guidelines.

History

Earlier lobar models of the prostate gave way in the late twentieth century to McNeal's zonal model, which reconciled divergent anatomical views and became the standard framework for describing the gland. Mid-twentieth-century biochemical studies by Huggins and colleagues characterised the composition of prostatic and seminal-vesicle secretions.

Key figures

• John E. McNeal
• Charles B. Huggins

Seminal works

• mcneal-1981
• mcneal-1980
• huggins-1942

Frequently asked questions

What are the zones of the prostate?

In McNeal's model the prostate has a peripheral zone, a central zone around the ejaculatory ducts, a transition zone around the proximal urethra, a preprostatic sphincteric region, and a non-glandular anterior fibromuscular stroma.

What does the prostate contribute to semen?

It adds a slightly acidic, enzyme-rich secretion containing prostate-specific antigen, citrate, zinc, and acid phosphatase, and prostate-specific antigen helps liquefy the semen coagulum.