The Prostate Gland: Man’s Center of Gravity
The prostate gland is a mysterious male reproductive organ that can be a source of curiosity, anxiety, fear and potential trouble. Since this gland is a midline organ nestled deep within the pelvis, I like to think of it as man’s “center of gravity.”
Where exactly is the prostate gland?
The prostate gland is located behind the pubic bone and is attached to the bladder (above) and the urethra (below). The rectum is directly behind the prostate (which permits access for prostate exam). The prostate is situated at the crossroads of the urinary and reproductive tracts and completely surrounds the urethra, allowing its many ducts to drain into the urethra. The relationship between the prostate and the urethra can potentially be the source of problems for the older male. When a man ages, the prostate gland gradually enlarges. This prostate enlargement can constrict and block the urethra, giving rise to bothersome urinary symptoms.
What is the prostate, what purpose does it serve, and how does it function?
The prostate is a male reproductive gland that produces prostate fluid, a nutrient and energy vehicle for sperm. The prostate consists of glandular and fibro-muscular tissue enclosed by a capsule of collagen, elastin and smooth muscle. The glandular tissue contains the secretory cells that produce the prostate fluid.
Semen is a “cocktail” composed of prostate fluid mixed with secretions from the seminal vesicles and sperm from the epididymis. The seminal vesicle fluid forms the bulk of the semen. The seminal vesicles and vas deferens (tubes that conduct sperm from testes to prostate) unite to form the ejaculatory ducts.
At the time of sexual climax, prostate smooth muscle contractions squeeze the prostate fluid through prostate ducts at the same time as the seminal vesicles and vas deferens contractions squeeze seminal fluid and sperm through the ejaculatory ducts. These pooled secretions empty into the urethra (channel that runs from the bladder to the tip of the penis). Rhythmic contractions of the superficial pelvic floor muscles result in the ejaculation of the semen.
What are the zones of the prostate gland?
The prostate gland is comprised of different anatomical zones. Most cancers originate in the “peripheral zone” at the back of the prostate, which can be accessed via digital rectal exam. The “transition zone” surrounds the urethra and is where benign enlargement of the prostate occurs. The “central zone” surrounds the ejaculatory ducts, which run from the seminal vesicles to the urethra.
Curious facts about the prostate:
- The prostate functions to produce a milky fluid that serves as a nutritional vehicle for sperm.
- Prostate “massage” is sometimes done by urologists to “milk” the prostate to obtain a specimen for laboratory analysis.
- The prostate undergoes an initial growth spurt at puberty and a second one starting at age 40 or so.
- A young man’s prostate is about the size of a walnut, but under the influence of aging, genetics and testosterone, the prostate gland often enlarges and constricts the urethra, which can cause annoying urinary symptoms.
- In the absence of testosterone, the prostate never develops.
- The prostate consists of 70% glands and 30% muscle. Prostate muscle fibers contract at sexual climax to squeeze prostate fluid into the urethra. Excessive prostate muscle tone, often stress-related, can give rise to the same urinary symptoms that are caused by age-related benign enlargement of the prostate.
- Women have a female version of the prostate, known as the Skene’s glands.