Prostate Anatomy: Explore the Gland and Surrounding Structures

Last Updated on August 23, 2025 by Max

Introduction

The prostate is a small gland with a big impact. Weighing only 15–20 grams in young men—about the size of three almonds—it sits directly below the bladder and wraps around the urethra. Despite its modest size, it influences both urination and fertility. By their 60s, almost half of men experience urinary changes linked to prostate enlargement (Barry, M.J., 2020).

Understanding how the prostate interacts with surrounding structures makes sense of these changes. On this page, you’ll find an interactive diagram you can explore, along with a detailed guide explaining the anatomy. Together, they show why this walnut-sized gland plays such a central role in male health.

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Explore the Prostate: Interactive Diagram

Use the interactive diagram below to tap or hover over each part—the prostate, bladder, urethra, seminal vesicles, rectum, and surrounding nerves. Each label highlights what the structure does and how it relates to prostate health.

When you click a label, you’ll jump to the corresponding explanation below. This way, you can explore visually first, then read deeper details for context.

Explore the Prostate: Interactive Diagram

Tap or hover to learn. Click a label to open details, then jump to the full explanation below.

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Prostate Gland

The prostate begins as a walnut-sized gland weighing about 15–20 grams. With age, it often enlarges, sometimes exceeding 100 grams in advanced benign prostatic hyperplasia (BPH) (Barry, M.J., 2020). Located just beneath the bladder and wrapped around the urethra, it produces about 30% of semen. Its secretions are slightly alkaline, protecting sperm in the acidic vaginal environment. Surprisingly, sperm themselves account for less than 5% of semen; the rest comes from the prostate and seminal vesicles (Mann, T., 2020).

As the prostate grows, it compresses the urethra. Even a few extra grams of tissue narrow the passage enough to slow urine flow, explaining symptoms such as weak stream, hesitancy, or dribbling.

Bladder

The bladder is a muscular reservoir that stores urine, typically signaling fullness at 300 ml but capable of stretching close to 600 ml. Positioned directly above the prostate, its outlet passes through the gland. This setup means even modest prostate growth can disrupt normal emptying. Over time, the bladder muscle thickens and strains to push urine past the narrowed outlet. That stress often results in nocturia—waking up at night to urinate—which affects nearly 70% of men over 60 (Irwin, D.E., 2020).

Urethra

The urethra functions like a straw running straight through the prostate. Any gland enlargement squeezes this channel interfering with urine flow. Clinically, flow rates fall noticeably with only minor narrowing, which physicians measure using uroflowmetry (Gravas, S., 2022). The urethra also serves as the final pathway for semen, making it a shared channel for both urinary and reproductive systems.

Seminal Vesicles

The seminal vesicles, each about 5 cm long, sit behind the bladder and above the prostate. They contribute roughly 60% of semen volume, producing fluid rich in fructose—the primary energy source for sperm. Without this sugar, sperm lose motility and their ability to reach the egg (Mann, T., 2020). Prostaglandins in the vesicular fluid thin cervical mucus, further supporting fertilization. These glands’ close relationship with the prostate means inflammation or blockage often affects ejaculation.

Vas Deferens and Ejaculatory Ducts

The vas deferens is a muscular tube that propels sperm from the testes at speeds near 5 meters per hour during ejaculation (Carson, C.C., 2021). As it nears the prostate, it merges with the duct of the seminal vesicle to form the ejaculatory duct. These ducts pierce the prostate and empty into the urethra, mixing sperm with prostate and seminal vesicle secretions. Enlargement or swelling of the prostate can compress these ducts, altering semen volume and sometimes causing painful ejaculation.

Rectum

Directly behind the prostate lies the rectum, separated by only a thin tissue wall. This proximity allows physicians to assess the prostate with a digital rectal exam (DRE). Despite its simplicity, the DRE remains valuable; studies show it detects abnormalities in up to 18% of cases missed by PSA alone (Cornu, J.N., 2021). The rectum’s alignment with the gland also makes it a key access route for imaging and biopsies.

Nerves and Blood Supply

The prostate is enveloped by delicate networks of blood vessels and nerves. Among them are the cavernous nerves, critical for erectile function. Because these bundles run along the prostate’s capsule, surgery in this area must be extremely precise. Damage explains why erectile dysfunction sometimes follows prostate surgery. Advances like nerve-sparing prostatectomy protect these bundles, with studies showing potency preserved in more than 70% of properly selected patients (Walz, J., 2020).

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Why This Anatomy Matters. When you look at these structures together, the story becomes clear. The prostate’s location—beneath the bladder, around the urethra, and next to the seminal vesicles and rectum—makes it a central player in both urinary and reproductive health. As it grows, it not only disrupts urination but also alters semen flow, bladder function, and sometimes sexual performance. Recognizing this interplay explains why prostate disorders have such wide-ranging effects on quality of life.