Prostate Gland Development, Function, Secretion, & Regulation
Throughout early childhood the prostate gland is very small (about the size of a pea) but grows rapidly during puberty in response to the production of the male hormone testosterone.
In adults the prostate is about the size of a walnut and weighs around one ounce. A healthy human prostate is classically said to be slightly larger than a walnut. In actuality, it is approximately the size of a kiwifruit. The mean weight of the “normal” prostate in adult males is about 11 grams, usually ranging between 7 and 16 grams. It surrounds the urethra just below the urinary bladder and can be felt during a rectal exam. It is the only exocrine organ (relating to external secretion glands, such as sweat glands or salivary glands that release a secretion through a duct to the surface of an organ.) located in the midline in humans and similar animals.
The function of the prostate is to secrete a slightly alkaline fluid, milky or white in appearance, that usually constitutes 20–30% of the volume of the semen along with spermatozoa and seminal vesicle fluid. The alkalinity of semen helps neutralize the acidity of the vaginal tract, prolonging the lifespan of sperm. The alkalinization of semen is primarily accomplished through secretion from the seminal vesicles. The prostatic fluid is expelled in the first ejaculate fractions, together with most of the spermatozoa. In comparison with the few spermatozoa expelled together with mainly seminal vesicular fluid, those expelled in prostatic fluid have better motility, longer survival and better protection of the genetic material (DNA).
Function in Ejaculation
Ejaculation occurs in two stages, the emission stage and the expulsion stage. The emission stage involves the workings of several structures of the ejaculatory duct; contractions of the prostate gland, the seminal vesicles and the vas deferens push fluids into the bulbourethral glands. The semen is trapped here and it is at this point that males perceive to be the point of no return for orgasm. This may be more commonly known as a male feeling as though they are “about to come”. This stage is followed by the expulsion stage. Muscles at the base of the penis contract in order to propel the seminal fluid trapped in the bulbourethral glands through the urethra and expel it through the tip of the penis. The ejaculate is expelled in spurts, due to the movement of the muscles propelling it. These muscle contractions are related to the sensations of orgasm for the male.
Sperm is produced in the testes and enters the ejaculatory ducts via the vas deferens. As it passes by the seminal vesicles, a fluid rich in fructose combines with sperm. This addition nourishes the sperm in order to keep it active and motile. Seminal fluid continues down the ejaculatory duct into the prostate gland, where an alkaline prostatic fluid is added. This addition provides the texture and odor associated with semen. The alkalinity of the prostatic fluid serves to neutralize the acidity of the female vaginal tract in order to prolong the survival of sperm in this harsh environment. Semen is now a fructose-rich, alkaline fluid containining sperm as it enters the bulbourethral glands below the prostate. The bulbourethral glands secrete a small amount of clear fluid into the urethra before the ejaculate is expelled. The functions of this fluid are not entirely known but are suggested to aid in lubricating the male urethra in preparation for the semen during ejaculation. The amount of semen produced and expelled during ejaculation corresponds to the length of time that the male is sexually aroused before ejaculation occurs. The longer the period of arousal, the larger the amount of seminal fluid.
Ejaculation and orgasm may occur simultaneously, however they are not coupled, in that one may occur without the other. For example, a man may have a dry orgasm; there is no expulsion of ejaculate however the man still experiences orgasm. Also, paraplegics may ejaculate seminal fluid but not experience the sensation of orgasm.
The prostate does not have a capsule, rather an integral fibromuscular band surrounds it. It is sheathed in the muscles of the pelvic floor, which contract during the ejaculatory process.
The secretory epithelium is mainly pseudostratified, comprising tall columnar cells and basal cells which are supported by a fibroelastic stroma containing randomly orientated smooth muscle bundles. The epithelium is highly variable and areas of low cuboidal or squamous epithelium are also present, with transitional epithelium in the distal regions of the longer ducts. Within the prostate, the urethra coming from the bladder is called the prostatic urethra and merges with the two ejaculatory ducts.
The ejaculatory ducts (ductus ejaculatorii) are paired structures in the male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the urethra at the Colliculus seminalis. During ejaculation, semen passes through the prostate gland, enters the urethra and exits the body via the tip of the penis.
Prostatic secretions vary among species. They are generally composed of simple sugars and are often slightly alkaline. In human prostatic secretions, the protein content is less than 1% and includes proteolytic enzymes, prostatic acid phosphatase, and prostate-specific antigen. The secretions also contain zinc with a concentration 500–1,000 times the concentration in blood.
To work properly, the prostate needs male hormones (androgens), which are responsible for male sex characteristics. The main male hormone is testosterone, which is produced mainly by the testicles. Some male hormones are produced in small amounts by the adrenal glands. However, it is dihydrotestosterone that regulates the prostate.
Every man wants to know how to optimize testosterone–and with good reason. But while testosterone may be critical for men’s health and well being, it’s not the final word in the ideal male hormone profile. In fact, testosterone’s real offer is its ability to convert into to a much stronger male androgen, dihydrotestosterone (DHT). I’ve heard people say that testosterone is what makes a man a Man, but, more accurately, it’s DHT that makes a Man. Without adequate DHT men have no body hair at all (which is why companies that make hair removal products for men love DHT) and, more importantly, without adequate DHT the male sexual organs (including the prostate) fail to fully mature. This bad condition is compounded by low sex drive and impaired sexual function.
Some researchers consider testosterone merely a prohormone because of its relatively weak actions compared to other androgens, in particular DHT. Further, DHT is the final word on the male androgen chain and …the king of all male hormones.
How much stronger is DHT when compared to testosterone? Ten times stronger, DHT shows ten times the androgen receptor uptake of testosterone but more importantly, unlike testosterone, DHT isn’t converted into estrogen. Even better, DHT actually blocks the aromatase enzyme which converts testosterone into estrogens. Thus, in addition to being stronger than testosterone, DHT is a potent aromatase inhibitor. Physicians commonly blame DHT as the primary cause of a prostate enlargement but deeper analysis indicates the androgen-to-estrogen balance, along with overall androgen ratios, is the key factor with prostate issues. In addition to not being a cause of prostate issues, DHT may actually help shrink enlarged prostates.
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