Weighing around 1 ounce (30 grams), the prostate surrounds the urethra, the tube that carries urine from the bladder to the penis. It is vital for the proper functioning of the male reproductive system.
In this article, we will explain what the prostate does, its basic structure, and what medical conditions can affect the prostate.
What does the prostate do?
The male reproductive system
The prostate only appears in males. It secretes a fluid that keeps sperm alive while protecting them and the genetic code they carry.
The prostate contracts during ejaculation and squirts its fluid into the urethra.
During ejaculation, sperm travels along two tubes called vas deferens; they carry millions of sperm from the testes (where they are made) to the seminal vesicles.
The seminal vesicles are attached to the prostate and add extra fluid to the semen before it is sent down the urethra.
The site where the vas deferens meets the seminal vesicles is known as the ejaculatory duct.
The prostate contracts during ejaculation, closing off the opening between the bladder and urethra and pushing semen through at speed. This is why it is impossible to urinate and ejaculate at the same time.
The milky fluid produced by the prostate — prostatic fluid — makes up around 30 percent of the total fluid ejaculated (the rest is sperm and fluid from the seminal vesicles). Prostatic fluid protects sperm, helping them live longer and be more mobile. It contains a number of ingredients, including enzymes, zinc, and citric acid.
One of the enzymes in prostatic fluid is prostate-specific antigen (PSA); after ejaculation, PSA makes thickened semen runnier, helping sperm travel through it more easily, increasing their likelihood of successfully fertilizing an egg.
Although prostatic fluid is slightly acidic, the other components of semen make it alkaline overall; this is to counteract the acidity of the vagina and protect the sperm from damage.
Structure of the prostate
The prostate is surrounded by connective tissue containing many muscle fibers; this capsule makes the prostate feel elastic to the touch. Scientists often split the prostate into four zones that encircle the urethra like layers of an onion. Here they are listed from outermost to innermost.
Anterior fibromuscular zone (stroma) — made of muscular and fibrous tissue. Part of the capsule.
Peripheral zone — mostly situated toward the back of the gland, this is where most of the glandular tissue is.
Central zone — surrounds the ejaculatory ducts and makes up around one-quarter of the prostate's total mass.
Transition zone — this is the smallest part of the prostate and surrounds the urethra; it is the only portion of the prostate that continues to grow throughout life.
Conditions affecting the prostate
As men age, the prostate can become enlarged.
There are a number of ways in which the prostate can cause medical problems, including:
Enlarged prostate — also known as benign prostatic hypertrophy (BPH), this affects almost all men aged 50 or over.
It makes it difficult to urinate and, in rare, serious cases, can prevent urination entirely. Most commonly, the enlargement occurs in the transition zone.
Prostatitis — an inflammation of the prostate; this is sometimes caused by an infection.
Prostate medical tests
The prostate and its function can be tested in a range of ways:
Digital rectal examination — the doctor inserts a finger into the rectum and feels the prostate. This can detect lumps, nodules, and cancer.
Prostate-specific antigen (PSA) — blood tests can assess the levels of this protein. High levels indicate an increased risk of prostate cancer.
Prostate biopsy — a needle inserted into the prostate via the rectum can take a sample of tissue to be tested in the lab.
Prostate ultrasound — also called a transrectal ultrasound, a probe is inserted into the rectum, positioning it close to the prostate. Sometimes a biopsy is taken at the same time.
In a nutshell
The prostate, a small muscular gland, produces an important fluid that transports sperm and keeps them safe. Although not vital for life, the prostate is vital for reproduction.