A normal prostate wedges neatly into the crowded multifunctional area of a man's lower pelvis.
The prostate in men, like the breast in a woman, is a gland that produces and secretes fluid and controls the fluid's flow.
Cells lining the prostate gland make some of the semen that comes out of the penis at the time of sexual climax (orgasm).
Prostate-specific antigen (PSA) helps to keep semen liquid. PSA is an enzyme in the form of a glycoprotein produced mostly by cells lining the acini and ducts of the prostate gland.
A normal human male prostate is about the size of a small plum or walnut. The prostate sits above the base of the penis, below the urinary bladder, backing onto the front wall of the rectum.
The prostate evolved in this tight-wedged position to aid reproduction. The prostate not only makes some of the fluid for semen. It may also keep urine out out of the semen, and it enhances pleasurable sensations of arousal and orgasm.
Prostate, seminal vesicles, vas deferens.
In males a single pipe, the urethra, serves two functions, urination and ejaculation. The urethra runs from the bladder through the prostate to the tip of the penis. The section that runs through the prostate is called the prostatic urethra.
The prostate gland makes a third of the fluid in semen that a man ejaculates.
During ejaculation millions of sperm arrive in the prostatic urethra. The sperm are made in the testicles. Leading from each testis is a coiled mass of spermatic ducting called the epididymis (Greek: upon + testicle), which houses maturing sperm. The epididymis (below left) looks like the crest on a helmet. It connects to a tube called the vas deferens (Latin: carrying-away vessel).
Testis and Epidymis
Sperm lodge in the epididymis for several days. When sexual excitement triggers ejaculation, muscle contractions in the wall of the vas deferens suck the sperm from the epididymis through to the vas deferens. As muscle contractions continue in waves the sperm rocket up towards and around the bladder and down by the two seminal vesicles into the prostatic urethra.
Some of the prostate is made of muscle. When sperm reach the prostatic urethra the prostate contracts, This may pinch a duct to the bladder so that sperm are kept urine-free. The contraction helps secrete prostatic fluid into the urethra and may also help expel the ejaculate.
Fluids from the prostate, the seminal vesicles, and Cowper's glands make up the bulk of semen. They flow into the prostatic urethra around the sperm. The semen is propelled along the urethral tube and out of the penis.
Protective Sea of Citrate, Zinc & Other Nutrients
Fluids in semen makes a protective sea to nourish the sperm and shield them from the acidic environment of the female vagina.
"The vagina is mildly acidic (~pH 4), sufficiently acidic to protect against many types of pathogens. But sperm are acid-sensitive, so semen is alkaline and the ejaculate abolishes the protective acidity of the vagina for many hours after intercourse. Otherwise sperm would be killed within seconds by vaginal acidity." Richard A. Cone. Visit his lab's webpage.
- Cowper's gland fluid lubricates the urethra.
- Seminal vesicle secretions are rich in fructose (an energy source for sperm), prostaglandins (from fatty acids) and proteins that help clot the semen in the female vagina.
- Prostate secretions are rich in calcium, zinc, citric acid, acid phosphatase, albumin, and prostatic specific antigen (PSA). In normal prostatic fluid citrate is high.
- A study finds that citrate is more than twice as low in prostate fluid of men with prostate cancer than in men without prostate cancer.
- Prostatic fluid gives semen its milky color.
The prostate has the highest concentration of citrate of any tissue in the human body. Scientists say they don't really know why this is, or what it does. They believe it has a role in reproduction, as yet unknown.
Zinc is also found in the prostate at high concentrations. Zinc is used as an antiseptic in everything from diaper rash ointment to cold remedies. Scientists think it has some role in fighting bacterial infection in the prostate.
The PSA in prostatic fluid, at the appropriate time, undoes the effect of the clotting enzyme derived from seminal vesicle fluid. The clotting enzyme makes the ejaculate gel and "glues" the semen in place by the female's cervix in her vagina. For a few minutes the sperm stay inside this gel. Within 15 to 30 minutes, PSA enzyme in the semen dissolves the clot and frees the sperm to swim into the uterus.
"This has an obvious advantage in reproduction. The sperm are in the best place to increase the chances of fertilization." (The Prostate Cancer Charity, Prostatic Fluid).
Prostate Problems
Unfortunately, if the prostate swells or enlarges, its wedged-in location and dual-purpose core tubing turn into a liability.
Two conditions, prostatitis (an acute or chronic infection) and BPH (benign swelling of the prostate) can cause discomfort and pain and trouble with urination. Prostatitis can occur at any age.
BPH, an overgrowth of normal (benign) prostate cells, typically occurs after the male reproductive peak has passed, in middle age and beyond. Although BPH responds to medication quite often it requires surgery.
If cancer cells develop in the prostate, a man's long term health or even his life may be at risk. Symptoms may not be felt for months or years. By the time urinary bother develop--with symptoms like BPH--typically a tumor is quite advanced. Don't wait for symptoms!
Urologists today can help men manage slow-growing prostate cancer by means of intelligently planned programs of regular tests and observation called "active surveillance."
More aggressive cancer can be treated if identified promptly at an early stage.
This page made by J. Strax December 26, 2006. Last updated April 26, 2015.
Resources and Links
Gray's Anatomy Illustrations ( Henry Gray (1825-1861). Anatomy of the Human Body. 1918.) online at bartleby.com and at wikipedia.org
GUIDELINES
Prostate Cancer Treatment Guidelines for Patients .pdf
English. Version 1, 2014 National Comprehensive Cancer Network (NCCN)
Cáncer de la próstata Guías de la NCCN para el tratamiento de los pacientes .pdf Septiembre de 2005 Transferencia directa aquí.
Nota! NCCN no ha actualizado sus gudielines español. El .pdf a continuación puede ser útil, pero fue publicado en 2005 y actualizado.
Direct link to National Comprehensive Cancer Network
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