The Genitourinary System and the Prostate

Opening Story

James, a 62-year-old retired teacher, went to his doctor because he was waking up three or four times a night to urinate. "I thought it was just part of getting older," he says. "I had no idea there was a small organ the size of a walnut causing all this trouble — or that understanding it would become so important to me." Like James, most men go through life without thinking about their prostate — until something goes wrong. This chapter will help you understand the system your prostate belongs to, what the prostate does, and what can go wrong with it even before cancer enters the picture.

The Genitourinary System: The Big Picture

The term "genitourinary" (GU) combines two systems that are closely connected in the male body: the urinary system (which makes and removes urine) and the genital or reproductive system (which produces sperm and enables reproduction). These two systems share some of the same "plumbing," which is why problems in one can affect the other.¹

The Urinary System

The urinary system is your body's filtration and waste-removal system. It includes:

• Kidneys (2): Bean-shaped organs located in the back of your abdomen, one on each side of your spine. They filter your blood, remove waste products, and produce urine. Each kidney is about the size of your fist.
• Ureters (2): Thin tubes, each about 10–12 inches long, that carry urine from each kidney down to the bladder.
• Bladder (1): A hollow, balloon-like organ in the lower abdomen that stores urine. It can hold about 400–600 mL (roughly 2 cups) of urine comfortably.
• Urethra (1): The tube that carries urine from the bladder out of the body. In men, the urethra is about 8 inches long and passes through the prostate gland and the penis. In women, it is much shorter (about 1.5 inches). This is important: because the male urethra passes directly through the prostate, any enlargement of the prostate can squeeze the urethra and make urination difficult.¹ ²

The Male Reproductive System

The reproductive system produces, stores, and delivers sperm. It includes:

• Testes (testicles, 2): Oval-shaped organs inside the scrotum. They produce sperm and the male hormone testosterone. Testosterone is the main hormone that drives prostate growth — both normal and abnormal.
• Epididymis (2): A coiled tube sitting on top of each testicle where sperm mature and are stored.
• Vas deferens (2): Muscular tubes that carry mature sperm from the epididymis up into the pelvis, where they join the urethra near the prostate.
• Seminal vesicles (2): Small glands located behind the bladder and above the prostate. They produce a sugar-rich fluid (containing fructose) that provides energy for sperm. The seminal vesicles contribute about 60–70% of the total ejaculate volume.²
• Prostate gland (1): A walnut-sized gland that sits just below the bladder and in front of the rectum. It surrounds the upper part of the urethra. The prostate produces about 15–30% of the seminal fluid — the liquid portion of semen.¹
• Bulbourethral glands (Cowper's glands, 2): Pea-sized glands below the prostate that produce a small amount of clear fluid before ejaculation, which lubricates the urethra.²

The Prostate: Your Most Important Gland (For This Book)

What is it?

The prostate is a gland — meaning it produces and secretes fluid. It is roughly the size and shape of a walnut in younger men (about 20 grams, or less than an ounce). It is composed of glandular and stromal elements tightly fused within a pseudocapsule, with an inner layer of smooth muscle and an outer layer of collagen.¹ It sits in a very "busy" neighborhood:

• Above it: the bladder
• Below it: the urinary sphincter (the muscle that controls urine flow)
• Behind it: the rectum (this is why doctors can feel the prostate through a rectal exam)
• Through it: the urethra (the tube that carries urine and semen out of the body)
• Behind and above it: the seminal vesicles¹ ²

Who has a prostate?

Only people born with male anatomy have a prostate. This includes transgender women (male-to-female), who retain their prostate even after gender-affirming surgery. This is important because transgender women can still develop prostate conditions, including prostate cancer, and should discuss screening with their doctors.³

What does the prostate do?

The prostate has one main job: to help with reproduction. It does this by:

1. Producing prostatic fluid: This slightly acidic fluid is rich in zinc, citric acid, and an enzyme called prostate-specific antigen (PSA). PSA liquefies semen after ejaculation, freeing the sperm to swim toward the egg. Without PSA, semen would remain thick and gel-like, trapping the sperm.¹
2. Nourishing and protecting sperm: The prostatic fluid contains substances that nourish sperm and protect them from the acidic environment of the female reproductive tract.
3. Producing prostasomes: These are tiny particles released by prostate cells that attach to sperm and help protect them from the immune system in the female body, improve sperm movement, and prevent premature activation of the sperm.
4. Acting as a valve: During ejaculation, the prostate (along with the bladder neck) closes off the connection to the bladder, preventing urine from mixing with semen and ensuring semen travels forward through the urethra.

The Zones of the Prostate

The prostate is not one uniform piece of tissue. In the 1980s, a pathologist named Dr. John McNeal described four distinct zones, each with different characteristics and disease tendencies:¹ ⁴

1. Peripheral zone (PZ): The largest zone, making up about 70% of the glandular tissue. It wraps around the back and sides of the prostate. This is where about 70% of prostate cancers develop. It is also the zone most easily felt during a digital rectal exam (DRE).¹ ²
2. Transition zone (TZ): A small zone (about 5% of the gland in young men) that surrounds the urethra in the middle of the prostate. This is the exclusive site where benign prostatic hyperplasia (BPH) develops. As BPH grows, this zone can expand dramatically and squeeze the urethra.¹ ²
3. Central zone (CZ): Makes up about 25% of the gland. It surrounds the ejaculatory ducts. Cancer rarely starts here.¹
4. Anterior fibromuscular stroma: The front surface of the prostate, made of muscle and fibrous tissue rather than glandular tissue. It does not produce fluid and is not a common site for cancer. The anterior fibromuscular stroma reinforces the prostatic stroma ventrally.⁵

Blood Supply, Nerves, and Lymphatics

• Blood supply: The prostate receives its blood from branches of the internal iliac artery (a major artery in the pelvis). Blood drains through a network of veins called the prostatic venous plexus, which connects to veins around the spine. This venous connection is one reason prostate cancer can spread to the bones of the spine and pelvis.¹
• Nerve supply: The prostate is supplied by nerves from the prostatic plexus, which carries both autonomic (involuntary) nerve fibers. These nerves come from spinal levels T11–L2 (sympathetic, "fight or flight") and S2–S4 (parasympathetic, "rest and digest"). Autonomic fibers are distributed in a spray-like pattern into the neurovascular bundle, the proximal plate, and accessory pathways.⁵ Critically, the neurovascular bundles — bundles of nerves and blood vessels — run along the back and sides of the prostate in a "neural hammock" configuration.⁵ These bundles contain the cavernous nerves that control erections. Parasympathetic nerves are most abundant in the dorsolateral regions of the prostate, while blood vessels have a more uniform distribution throughout the gland.⁶ This is why prostate surgery and radiation therapy can affect erectile function, and why surgeons try to spare these bundles when possible.⁵
• Lymphatic drainage: Lymph fluid from the prostate drains primarily to the internal iliac lymph nodes in the pelvis. When prostate cancer spreads to lymph nodes, these are usually the first ones affected.¹

How the Prostate Changes with Age

The prostate is one of the few organs in the body that continues to grow throughout a man's life. Understanding this is important because it explains why urinary problems become more common as men age.

• At birth: The prostate weighs about 1.5 grams — tiny.
• At puberty: Under the influence of rising testosterone levels, the prostate undergoes its second growth spurt, reaching about 10 grams in early puberty and approximately 20 grams by age 20.
• Ages 20–40: The prostate remains relatively stable in size.
• After age 40: A third growth phase begins, but unlike the earlier phases, this growth is selective — it occurs mainly in the transition zone (the area around the urethra). This is the beginning of benign prostatic hyperplasia (BPH).⁷
• By age 50: About 50% of men have evidence of BPH on autopsy.⁷ ⁸
• By age 60: More than 50% of men experience urinary symptoms from prostate enlargement.⁹
• By age 70–80: Up to 80–90% of men have BPH, and many have significant urinary symptoms.⁷ ⁸ ⁹

Non-Cancer Conditions of the Prostate

Before we discuss prostate cancer (Chapter 2), it is important to understand that the prostate can cause problems that have nothing to do with cancer. In fact, the most common prostate conditions are benign (non-cancerous).

1. Benign Prostatic Hyperplasia (BPH)

BPH is the most common prostate condition. It is not cancer, and having BPH does not increase your risk of developing prostate cancer.⁹

What is it? BPH is an overgrowth of the cells in the transition zone of the prostate. As this zone enlarges, it squeezes the urethra (like stepping on a garden hose) and can push up against the bladder, causing urinary symptoms.¹ ²

How common is it? BPH is extremely common. BPH has an estimated global incidence of 280 per 100,000 and prevalence of 2,480 per 100,000 based on the 2019 Global Burden of Disease study.⁸ The histologic prevalence increases dramatically with age:⁷ ⁸ ⁹

• 8% of men in their 40s
• 40% of men in their 50s
• 70% of men in their 70s
• Up to 90% of men aged 80 and older

However, not all men with BPH develop symptoms. BPH is found during autopsy in approximately 50% of men aged 51 to 60 years and up to 90% of men aged 80 years or older, but only about 50% of men aged 75 with BPH report symptoms.⁸

What causes it? The exact cause is not fully understood, but it requires two things: aging and the presence of androgens (male hormones), particularly dihydrotestosterone (DHT), which is made from testosterone by an enzyme called 5-alpha reductase. Men who are castrated before puberty or who lack 5-alpha reductase do not develop BPH.⁹ Chronic inflammation within the prostate also appears to play a role.

Growth patterns: BPH can grow in different patterns:

• Lateral lobe enlargement: The sides of the transition zone grow, squeezing the urethra from both sides.
• Median lobe enlargement: A lobe grows upward into the bladder, acting like a ball valve at the bladder outlet. This pattern can cause particularly bothersome symptoms even with a relatively small prostate.

Symptoms of BPH are divided into two categories:⁸ ⁹

Obstructive (voiding) symptoms:

• Weak urinary stream
• Hesitancy (difficulty starting urination)
• Straining to urinate
• Intermittent stream (stopping and starting)
• Feeling of incomplete emptying
• Dribbling at the end of urination

Storage (irritative) symptoms:

• Urinary frequency (going too often)
• Urgency (sudden strong need to urinate)
• Nocturia (waking at night to urinate)
• Urge incontinence (leaking before reaching the toilet)

When to worry: Most men with BPH can manage their symptoms with lifestyle changes or medications. However, some men develop complications such as:⁷

• Urinary retention (inability to urinate at all — a medical emergency)
• Recurrent urinary tract infections
• Bladder stones
• Kidney damage (rare, from chronic obstruction)

Treatment options for BPH (brief overview):⁸ ⁹

• Lifestyle changes (limiting fluids before bed, reducing caffeine/alcohol)
• Medications: alpha-blockers (e.g., tamsulosin) to relax prostate muscle, 5-alpha reductase inhibitors (e.g., finasteride, dutasteride) to shrink the prostate
• Minimally invasive procedures (e.g., UroLift, Rezūm water vapor therapy, prostatic arterial embolization)⁷
• Surgery (e.g., TURP — transurethral resection of the prostate)

2. Prostatitis

Prostatitis means inflammation of the prostate. It affects approximately 9.3% of men at some point in their lives.¹⁰ Unlike BPH, prostatitis can affect men of any age, including young men, with a mean age of onset of 42 years.¹¹

The National Institutes of Health (NIH) classifies prostatitis into four types:¹⁰

Type I — Acute Bacterial Prostatitis:

• A sudden, severe infection of the prostate
• Symptoms: fever, chills, severe pain in the pelvis or lower back, painful urination, difficulty urinating
• The prostate feels tender, swollen, and "boggy" on rectal exam
• Caused by gram-negative bacteria (usually E. coli or similar organisms) in 80–97% of cases¹⁰
• Treatment: broad-spectrum antibiotics for 2–4 weeks (e.g., ciprofloxacin, ceftriaxone, or piperacillin-tazobactam), with a 92–97% success rate¹⁰
• This is a medical emergency if severe

Type II — Chronic Bacterial Prostatitis:

• A persistent or recurring bacterial infection of the prostate
• Symptoms: recurring urinary tract infections with the same bacteria, pelvic pain, painful urination
• Treatment: prolonged antibiotics (at least 4–6 weeks), often fluoroquinolones¹⁰
• Up to 74% of cases are caused by gram-negative bacteria like E. coli¹⁰

Type III — Chronic Prostatitis / Chronic Pelvic Pain Syndrome (CP/CPPS):

• The most common form, accounting for over 90% of prostatitis cases¹¹
• Symptoms: pelvic pain lasting at least 3 months, urinary symptoms, sometimes sexual dysfunction
• No bacteria are found on testing
• The cause is unclear — it may involve nerve sensitivity, muscle tension, inflammation, or psychological factors
• Treatment is multimodal: alpha-blockers (first-line for urinary symptoms), anti-inflammatory medications, pelvic floor physical therapy, stress management¹⁰
• This condition can be very frustrating because it is difficult to treat and tends to come and go

Type IV — Asymptomatic Inflammatory Prostatitis:

• No symptoms at all
• Found incidentally when prostate tissue is examined for other reasons (e.g., during a biopsy for elevated PSA)
• No treatment is needed¹⁰

Important note: Prostatitis can raise your PSA level, which can cause anxiety about cancer. If your PSA is elevated and prostatitis is suspected, your doctor may treat the infection first and then recheck the PSA.

3. Chronic Pelvic Pain Syndrome

This overlaps significantly with Type III prostatitis (above). It is a condition where men experience chronic pain in the pelvic area — including the perineum (the area between the scrotum and rectum), lower abdomen, lower back, or genitals — without a clear cause. It can significantly affect quality of life. Treatment often involves a combination of medications, physical therapy, and psychological support.¹¹

Myth vs. Fact

• Myth: "Only old men have prostate problems."

Fact: While BPH is more common with age, prostatitis can affect men of any age, even those in their 20s and 30s.¹⁰

• Myth: "BPH turns into cancer."

Fact: BPH and prostate cancer are separate conditions. BPH develops in the transition zone; most cancers develop in the peripheral zone. Having BPH does not increase your cancer risk.¹ ²

• Myth: "If I have urinary problems, it must be my prostate."

Fact: Urinary symptoms can come from many causes — bladder problems, infections, medications, diabetes, neurological conditions, and more. A proper evaluation is important.⁸

• Myth: "Women don't need to know about the prostate."

Fact: Partners and family members play a crucial role in supporting men with prostate conditions. Understanding the anatomy helps everyone communicate better with the medical team.

Questions to Ask Your Doctor

1. Is my prostate enlarged? If so, how large is it?
2. Are my urinary symptoms caused by my prostate, my bladder, or something else?
3. Do I need any tests to rule out prostate cancer?
4. What are my treatment options for BPH, and what are the side effects of each?
5. Could my medications be affecting my urinary symptoms?
6. Should I see a urologist?

Key Takeaways

1. The prostate is a walnut-sized gland that sits below the bladder and surrounds the urethra. Its main job is to produce fluid that nourishes and protects sperm.
2. The prostate grows throughout life. After age 40, this growth can squeeze the urethra and cause urinary symptoms — this is called BPH and is not cancer.
3. The prostate has four zones. Most cancers arise in the peripheral zone (back of the prostate), while BPH develops in the transition zone (around the urethra).
4. The neurovascular bundles that control erections run along the sides of the prostate — this is why prostate treatments can affect sexual function.
5. Prostatitis (prostate inflammation) can occur at any age and can raise PSA levels, sometimes mimicking cancer.

Support Resources

• Urology Care Foundation: www.urologyhealth.org — Patient guides on BPH, prostatitis, and prostate anatomy
• American Urological Association (AUA): www.auanet.org — Clinical guidelines and patient resources
• Prostate Cancer Foundation: www.pcf.org — Comprehensive information on all prostate conditions
• ZERO — The End of Prostate Cancer: www.zerocancer.org — Support and education
• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): www.niddk.nih.gov — Information on BPH and prostatitis

References

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