A walnut-sized gland encircling the first part of the male urethra, immediately below the bladder
Prostate gland — the prostatic urethra passes through it.
Anatomy · Glands & the immune system
Prostate gland
A walnut-sized gland surrounding the first part of the male urethra
Male reproductive system · pelvis, below the bladder
A firm, walnut-sized gland in the male pelvis that sits directly beneath the bladder, in front of the rectum and behind the pubic bones, wrapped around the first part of the urethra. The ejaculatory ducts pass through it. It secretes a thin, slightly alkaline, milky fluid containing citric acid, zinc and prostate-specific antigen (PSA), which forms roughly a third of the volume of semen. Because the urethra runs through its middle, enlargement of the gland squeezes the urine flow.
How to spot them
- ▸Chestnut- or walnut-shaped gland encircling the urethra just below the bladder neck
- ▸In front of the rectum, so its back surface can be felt through the rectal wall on examination
- ▸Seminal vesicles sit on its upper back surface and their ducts join the vas deferens to form the ejaculatory ducts that enter it
- ▸Divided into zones: a large peripheral zone at the back, a central zone, a transition zone around the urethra, and a fibromuscular front
- ▸Under the microscope, branching glands in a stroma rich in smooth muscle, often with pink concretions
What to know
Its back surface can be felt by a gloved finger through the wall of the rectum
Prostate gland — the digital rectal examination.
It adds a milky, slightly alkaline secretion, rich in citric acid and zinc, to about a third of the semen
Prostate gland — prostatic fluid also contains PSA, which liquefies the coagulated semen.
Benign enlargement in older men squeezes the urethra, producing hesitancy and a weak stream
Prostate gland — benign prostatic hyperplasia, from the transition zone.
Most cancers of this gland arise in its peripheral zone at the back, which is the part felt on examination
Prostate gland — the peripheral zone is about 70% of the gland.
The paired ejaculatory ducts from the seminal vesicles and vas deferens pass through it to open into the urethra
Prostate gland — they enter at the seminal colliculus (verumontanum).
Its Greek name means 'one who stands before', from its position in front of another organ
Prostate gland — Greek prostates.
Key ideas
- The gland's secretion is released into the urethra during ejaculation, when smooth muscle in its stroma contracts to squeeze the fluid out. The prostatic fluid helps the sperm live in the acid environment of the vagina.
- PSA, a protease made by the prostate cells, breaks down the clotted semen so the sperm can swim free; a raised blood level of PSA is used as a screening marker.
Quick-fire facts
- •It weighs about 20 g in a young man and roughly doubles in size at puberty; from about age 25 it slowly enlarges again
- •Prostatic fluid is roughly a quarter to a third of semen volume; the seminal vesicles contribute the majority
- •McNeal's zones: peripheral (about 70% of glandular tissue), central (about 25%), transition (about 5%) and an anterior fibromuscular zone
- •Benign prostatic hyperplasia affects a large share of men by their sixties
- •Cancer of the prostate is the most common cancer in men in the UK
- •Nerves controlling erection run along its back sides, the neurovascular bundles, which surgeons try to preserve
- •Blood is supplied chiefly by the inferior vesical artery, and venous blood drains into the prostatic plexus and internal iliac veins
- •It has no counterpart in the female except the small Skene's (paraurethral) glands, sometimes called the female prostate
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