The prostate is an organ in male reproductive anatomy. This small gland sits directly below the bladder and plays a role in producing and fine-tuning semen.

The prostate has various functions. The most important is producing seminal fluid, a fluid that is a component of semen. It also plays a role in hormone production and helps regulate urine flow.

Prostate problems are common, especially in older men. The most common include an inflamed prostate, an enlarged prostate, and prostate cancer.

Symptoms of prostate trouble often appear as difficulty urinating, which might include poor bladder control or weak urine flow.

This article provides an overview of the prostate, including its function and structure, where it is, and what medical conditions can affect it.

The prostate is a small, soft organ. On average, it is roughly the size of a walnut or a ping-pong ball. It weighs around 1 ounce (30 grams) and is usually soft and smooth to the touch.

The prostate sits deep in the pelvis, between the penis and the bladder. It is possible to feel the prostate gland by placing a finger into the rectum and pressing toward the front of the body.

The urethra, a tube that carries urine and semen out of the body, passes through the prostate. Because the prostate surrounds this tube, prostate problems can affect urine flow.

This organ is one part of male sexual, or reproductive, anatomy. The other parts include the penis, scrotum, and testes.

The prostate is not essential for life, but it is important for fertility. The following sections discuss the functions of the prostate.

Helping to produce semen

The primary function of the prostate is to contribute prostatic fluid to semen. According to one article, the prostate contributes between 20–30% of fluid to the total semen volume. The remainder comes from the seminal vesicles (50–65%) and the testicles (5%)

Prostatic fluid contains components that make semen an ideal substance for sperm cells to live in, including enzymes, zinc, and citric acid. One important enzyme is prostate-specific antigen (PSA), which helps make the semen thinner and more fluid.

The fluid in semen helps the sperm travel down the urethra and survive the journey towards an egg, which is essential for reproduction.

Prostatic fluid is slightly acidic, but other components of semen make it alkaline overall. This is to counteract the acidity of the vagina and protect the sperm from damage.

Closing the urethra during ejaculation

During ejaculation, the prostate contracts and squirts prostatic fluid into the urethra. Here, it mixes with sperm cells and fluid from the seminal vesicles to create semen, which the body then expels.

When the prostate contracts during ejaculation, it closes off the opening between the bladder and urethra, pushing semen through at speed. This is why, in normal anatomic situations, it is impossible to urinate and ejaculate simultaneously.

Hormone metabolism

The prostate needs androgens, which are male sex hormones, such as testosterone to function correctly.

The prostate contains an enzyme called 5-alpha-reductase, which converts testosterone into a biologically active form called dihydrotestosterone (DHT).

This hormone is important for normal prostate development and function. In the developing male, it is crucial for the development of secondary sex characteristics, such as facial hair.

A capsule of connective tissue that contains muscle fibers surrounds the prostate. This capsule makes the prostate feel elastic to the touch.

Scientists often categorize the prostate into four zones that surround the urethra like layers of an onion.

The following layers make up the prostate, beginning with the outer capsule and ending inside the prostate:

  • Anterior zone.Made of muscle and fibrous tissues, this zone is also called the anterior fibromuscular zone.
  • Peripheral zone. Mostly situated toward the back of the gland, this is where most of the glandular tissue sits.
  • Central zone. This surrounds the ejaculatory ducts and makes up around 25% of the prostate’s total mass.
  • Transition zone. This is the part of the prostate that surrounds the urethra. It is the only portion of the prostate that continues to grow throughout life.

Prostate conditions often cause problems with urination or bladder control. These may include the following:

  • poor bladder control, including frequent bathroom visits
  • urinary urgency, sometimes with only a small amount of urine
  • difficulty starting the urine stream, or stopping and starting the stream while urinating
  • a weak or thin urine stream

Prostate problems can also cause problems with sexual function, urinary tract infections, bladder stones, or in extreme cases, kidney failure.

If a person is unable to urinate at all, they should seek medical attention immediately.

A person should see their doctor if they notice any of the following symptoms:

  • pain while urinating or after ejaculation
  • pain in the penis, scrotum, or the area between the scrotum and anus
  • blood in the urine
  • severe discomfort in the abdomen
  • a weak urine stream or dribbling at the end of urinating
  • fever, chills, or body aches
  • trouble controlling the bladder, such as stopping or delaying urination
  • unable to empty your bladder completely
  • urine with an unusual odor or color

Several medical problems can affect the prostate, including the following:

Prostatitis

Prostatitis is a common swelling or inflammation of the prostate. This is the most common prostate problem in males under 50.

Acute prostatitis is a sudden inflammation of the prostate. This can occur due to a bacterial infection. It appears suddenly and clears up quickly with appropriate antibiotic treatment.

When prostate inflammation lasts for longer than 3 months, it is known as chronic prostatitis, or chronic pelvic pain syndrome. This affects 10–15% of males in the U.S.

Enlarged prostate

An enlarged prostate, also known as benign prostatic hypertrophy (BPH), is the most common prostate problem in males over 50.

Most commonly, the enlargement occurs in the transition zone.

When the prostate enlarges, it presses and pinches the urethra, narrowing the urethra tube. The narrowing of the urethra and a reduced ability to empty the bladder cause many of the problems linked with this condition. As this condition persists, the bladder may become weaker and be unable to empty properly.

An enlarged prostate makes it difficult to urinate and, in rare, serious cases, can prevent urination entirely. This is a condition called urinary retention, which requires urgent medical evaluation.

Read about ways to shrink an enlarged prostate here.

Prostate cancer

According to the American Cancer Society, prostate cancer is the most common form of cancer in males after skin cancer. It affects around 1 in 9 males during their lifetime.

On average, people receive a prostate cancer diagnosis at age 66.

The American Cancer Society state that people can choose whether to get a prostate cancer screening based on their age and risk factors, but that they should be aware of the potential risks of testing beforehand.

Medical professionals can diagnose problems with the prostate using various types of prostate exams.

Common prostate exams include:

  • Digital rectal examination. The doctor inserts a finger into the rectum and feels the prostate to detect lumps, nodules, and signs of cancer.
  • Prostate-specific antigen (PSA). Blood tests can assess the levels of this PSA. High levels indicate an increased risk of prostate cancer.
  • Prostate biopsy. If a doctor suspects cancer, they can take a small sample of prostate tissue for testing. To do this, they insert a needle into the prostate via the rectum.
  • Prostate ultrasound. Also called a transrectal ultrasound, the doctor inserts a probe into the rectum, positioning it close to the prostate. Doctors usually carry out biopsies with guidance from an ultrasound.
  • Prostate MRI. This can show prostate anatomy in great detail, including identifying areas suspicious for cancer. New technology allows targeting of these areas through an MRI-ultrasound fusion biopsy.

The prostate is a small muscular gland in male reproductive anatomy. It produces an important fluid that helps transport sperm and keeps them safe.

Although not essential for life, the prostate is important for reproduction.

If a person suspects a problem with their prostate, they can speak to a doctor for accurate diagnosis and treatment recommendations.