prostate
Meaning of prostate: Its position explains its symptoms, since a gland wrapped around the urine channel cannot enlarge or inflame without the stream noticing.
Definition of prostate
The prostate is a gland of the male reproductive system, sitting just below the bladder and wrapped around the top of the urethra, the tube carrying urine and semen out of the body. It produces a thin fluid that mixes with sperm and with secretions from other glands to form semen. It is normally about the size of a walnut.
What does the prostate do?
The gland contributes a substantial share of the volume of semen. Its secretion is thin and slightly alkaline, and it contains enzymes including prostate specific antigen, which keeps semen liquid after ejaculation. The alkalinity helps counter the acidity a sperm cell encounters on its way. Muscle fibers within the gland contract during ejaculation to push this fluid into the urethra, and the same muscle helps close the bladder neck at that moment so that semen travels outward rather than backward into the bladder. Growth and upkeep of the gland depend on male hormones, which is why blocking those hormones causes it to shrink.
Why does it affect urination so readily?
The urethra passes directly through the middle of the gland on its way down from the bladder. Anything that enlarges the gland or makes it swell therefore squeezes the channel it surrounds, and there is little room to expand outward because a firm capsule encloses the whole structure. That single anatomic fact explains why urinary symptoms are the common thread running through otherwise unrelated prostate conditions, and equally why those symptoms do not distinguish between them.
What conditions arise in it?
| Condition | What it is | Where it starts |
|---|---|---|
| Benign prostatic hyperplasia | Noncancerous enlargement, very common with age | The inner zone immediately around the urethra |
| Prostatitis | Inflammation, sometimes from infection and often not | Variable, frequently diffuse |
| Prostate cancer | Malignant growth, often slow to develop | Most often the outer zone, away from the urethra |
The zones deserve attention. Benign enlargement develops in the tissue immediately surrounding the urethra, which is why it obstructs flow early and noticeably. Cancer arises most often in the outer part of the gland, well away from the urethra, which is why it can grow for a long period without altering urination at all. That difference is one reason urinary symptoms are a poor guide to which condition is present, and why examination, blood testing and imaging are used instead of symptoms alone.
Used in a sentence
The urologist examined the prostate as part of the evaluation for the patient's urinary symptoms.
Good to know
Benign prostatic hyperplasia, a common noncancerous enlargement of the prostate with age, can cause urinary symptoms that overlap with those of prostate cancer, which is why symptoms alone do not distinguish between the two.
Word origin
Where “prostate” comes from
From Greek prostates, meaning one who stands before, formed from pro-, meaning before, and histanai, meaning to stand, describing the gland's position in front of the bladder outlet.