The Anatomy of the Prostate

The prostate secretes fluid that protects and nourishes sperm

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The prostate is an important gland located between the penis and bladder. It sits just to the front of the rectum. The urethra, which carries urine from the bladder out of the body, runs through the center of this walnut-sized organ.

Primarily, this gland serves the function of secreting fluid that nourishes sperm and keeps it safe.

Some health conditions that affect the prostate include:

This article explains the anatomy, function, and common conditions of the prostate and some common tests associated with the organ.

Prostate gland. Male reproductive and urinary systems.
ChrisChrisW / Getty Images

Anatomy

The prostate is located within the lesser pelvis. It sits just beneath the bladder and to the front of the rectum.

The prostate is surrounded by a fibrous layer called a capsule. It wraps around the proximal (more central) portion of the urethra. The seminal vesicles run above and behind this gland.

Its shape is cone-like. The base of the prostate surrounds the neck of the urinary bladder, and the apex (highest point) sits below the sphincter.

Lobes

Anatomically speaking, the prostate consists of five distinct lobes:

  • Anterior lobe: This front portion is positioned right in front of the urethra. It consists of fibromuscular—rather than glandular—tissue.
  • Median lobe: This is a cone-shaped portion of the prostate. The median lobe sits between the two ejaculatory ducts (which deliver sperm to the seminal vesicles) and the urethra.
  • Lateral lobes: The right and left lateral lobes comprise the majority of the body of the prostate. Their rear (posterior) ends are continuous. They’re separated by the prostatic urethra, which is the widest part of the urethra.
  • Posterior lobe: The rear-facing lobe of the prostate is connected to the lateral lobes. This is the part of the prostate that your doctor feels when they examine your prostate.

Zones

This gland is also considered to be divided into several different zones, including:

  • Central zone: This portion of the prostate surrounds the ejaculatory ducts. It makes up 25% of its mass.
  • Peripheral zone: Making up 70% of this organ, this zone surrounds a majority of the central zone. It also wraps around a portion of the prostatic urethra.
  • Transition zone: This smaller portion represents 5% of the prostate. It encircles the part of the urethra between the urinary bladder and verumontanum, a structure towards the floor of the urethra.

Several tubular structures pass through the prostate. These include the proximal urethra and two ejaculatory ducts.

The ejaculatory ducts enter the prostate where it emerges from the seminal vesicles. Both structures come together at a portion of the urethra within the prostate called the “seminal colliculus.”

Anatomical Variations

Occasionally, doctors find congenital variations in the anatomy of the prostate. That means the gland develops irregular features.

Though relatively uncommon, the median lobe of this gland is sometimes absent. When that happens, the anterior and lateral lobes are directly connected.

In addition, some people are born with an extra lobe to this gland.

Recap

The prostate is shaped like a cone. It sits between the penis and bladder, just in front of the rectum. It has five lobes, three zones, and several tubes that pass through it. Anatomical variations, such as missing or extra lobes, are uncommon but can occur.

Function

The prostate is a supportive organ of the male reproductive system. It serves an essential function in the health and maintenance of sperm.

The primary role of this gland is to secrete an alkaline solution that surrounds sperm. This fluid from the prostate contains an enzyme called "prostate-specific antigen" (PSA). It neutralizes the area immediately surrounding sperm that have accessed the prostate.

The solution protects sperm when it enters the acidic environment of the vagina during sex. This allows sperm a longer amount of time to access the egg. Furthermore, fluids from the prostate work to nourish and feed sperm.

These functions are essential for the process of conception. PSA plays a vital role in male fertility. That's because it helps increase the motility of sperm.

Essentially, prostate fluid combines with other fluids in the urethra to make up semen. These include:

  • Sperm from the testicles
  • Fluids from the seminal vesicles
  • Fluids from the bulbourethral gland (a small gland beneath the prostate)

Recap

The role of the prostate is to provide fluid to protect sperm. This protective fluid gives it extra time to reach the egg during reproduction.

Associated Conditions

Several major health conditions affect the prostate. Cancer is one of them. However, some conditions that affect the prostate are benign (non-cancerous).

Benign Prostatic Hyperplasia (BPH)

One of the most common issues that arise with this gland is benign prostatic hyperplasia (BPH). This condition is especially common in older people. It is characterized by an enlarged prostate.

An enlarged prostate can narrow the urethra or lead to it pressing up against the bladder. This can cause symptoms such as:

  • Frequent urination
  • Nocturia (needing to get up at night to urinate)
  • Weak urine stream

Treatment approaches tend to be more conservative. They may include:

  • Alpha-1 receptor blocker drugs can help reduce smooth muscle tone in the urethra to improve the passage of urine. 
  • 5-alpha-reductase inhibitors, which may be prescribed to reduce hormone production in the prostate and shrink its size. 

Prostate Cancer

Especially in the initial presentation, this condition can mimic BPH. However, with prostate cancer, you might experience lower back pain, as well. Like other cancers, prostate cancer can spread to other organs.

Those most at risk of developing prostate cancer include:

  • Current or former smokers
  • Those with a family history of cancer
  • People with a higher body mass index (BMI)
  • Those who’ve been exposed to radiation
  • Being older

Prostate Cancer Risk Increases With Age

People over age 55 are more likely to develop prostate cancer, but more often, it occurs even later. In fact, 60% of prostate cancers occur in people over age 65.

There is a wide range of treatment options for this condition. These include:

  • Prostatectomy is the surgical removal of the gland. It is performed either robotically or using laparoscopic methods.
  • Radiation therapy uses radio waves to kill cancerous tumors.
  • Chemotherapy uses drugs that target and kill cancer cells. These may be taken orally or intravenously.

Prostatitis

Bacterial infection of the prostate is called prostatitis. This condition can lead to pain in the prostate.

This disease can be difficult to diagnose. That's because the same kind of bacteria can also lead to urinary tract infection (UTI). However, antibiotic treatments are highly effective in solving the problem.

Tests

A urologist is a doctor that specializes in the urinary tract and male reproductive organs, including the prostate. They can assess the health of the prostate in a variety of ways.

Procedures vary from physical examination to the use of imaging technologies. Here’s a quick breakdown of some of the most common approaches.

Digital Rectal Examination (DRE)

The first-line approach to prostate health assessment is the digital rectal examination. Wearing gloves and lubricating their hand, the doctor will ask you to lay over an examination table. They will then insert a finger into the rectum to feel the prostate.

This exam checks for inflammation or any other irregularities in shape. Though uncomfortable, the procedure is brief, and it’s a routine part of health examination for people with a prostate who are 50 and older.

Prostate-Specific Antigen (PSA) Test

The PSA test assesses levels of PSA within the bloodstream. It’s recommended for people over 50 or those who have other risk factors for prostate cancer.

Abnormally high levels of PSA in the blood can be a sign of cancer. So positive results tend to warrant further investigation.

Urinalysis

Your doctor may perform a urine analysis to diagnose prostatitis or the presence of abnormal substances in the prostate. This test can also help differentiate between urethral and prostate infection.

In addition, your doctor can assess the overall function of the prostate, urethra, and bladder with urodynamic testing. This test looks at the flow of urine as well as storage capacity.

Abdominal Ultrasound

Ultrasound involves the use of benign sound waves to map structures in the abdomen, including the prostate.

A gel is applied to the abdomen during an ultrasound, and a hand-held device called a transducer is moved over the area. Then, specialists examine the images captured to get an overall sense of the health of the organ.

Prostate Biopsy

When previous tests have unearthed potential cancer, your doctor may do a biopsy guided by ultrasound. This can confirm the diagnosis.

Using ultrasound imaging as a guide, your doctor will collect a tissue sample with a needle from the prostate. A lab technician will then assess the sample for the presence of cancer cells. 

Imaging Scans

Doctors also rely on a variety of imaging techniques used to diagnose prostate issues. These may include:

These approaches can help detect abnormal growths. However, a biopsy is often necessary to confirm cancer.

Summary

The prostate is a small organ that sits between the penis and the bladder. Its main function is to coat sperm with a protective liquid to have adequate time to reach the egg during reproduction.

The prostate may become enlarged or infected. Cancer can also affect the prostate. Cancer most often affects people older than 55.

A prostate exam is a routine part of healthcare screening after age 50. If you have symptoms of a problem with your prostate, including frequent urination, weak stream, or low back pain, your doctor may perform other screening tests, as well.

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Article Sources
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