View source for Prostate

{{BioPsy}}

{{Refimprove|date=June 2008}}{{Infobox Anatomy |
  Name         = Prostate |
  Latin        = prostata |
  Image        = Prostatelead.jpg |
  GraySubject  = 263 |
  GrayPage     = 1251 |
  Caption      = Male Anatomy |
  Image2       = Gray1160.png |
  Caption2     = Prostate with [[seminal vesicles]] and [[seminal ducts]], viewed from in front and above. |
  Width        = 300 |
  System       = |
  Artery       = [[internal pudendal artery]], [[inferior vesical artery]], and [[middle rectal artery]] |
  Vein         = [[prostatic venous plexus]], [[pudendal plexus]], [[vesicle plexus]], [[internal iliac vein]]  |
  Nerve        = [[inferior hypogastric plexus]] |
  Lymph        = [[external iliac lymph nodes]], [[internal iliac lymph nodes]], [[sacral lymph nodes]] |
  Precursor    = [[Endodermic evaginations of the urethra]] |
  MeshName     = Prostate |
  MeshNumber   = A05.360.444.575 |
  DorlandsPre  = p_36 |
  DorlandsSuf  = 12671161  |
}}
The '''prostate''' (from Greek ''προστάτης'' - ''prostates'', literally "one who stands before", "protector", "guardian"<ref>[http://www.perseus.tufts.edu/cgi-bin/ptext?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3D%2390129 The term ''prostates'', Liddell and Scott, "A Greek-English Lexicon", at Perseus]</ref>) is a compound tubuloalveolar [[exocrine gland]] of the male [[mammal]]ian [[reproductive system]]. Women do not have a prostate gland, although women do have microscopic paraurethral [[Skene's gland]]s connected to the distal third of the urethra in the prevaginal space that are homologous to the prostate.

The prostate differs considerably among species [[anatomy|anatomically]], [[chemical]]ly, and [[physiology|physiologically]]. 

* Posterior: [[urethra]] and [[rectum]]
* Superior: upper surface of [[urogenital diaphragm]] and [[urinary bladder]]
* Lateral: anterior fibers of [[levator ani muscle]]

==Function==
The main function of the prostate is to store and secrete a clear, slightly [[base (chemistry)|alkaline]] (pH 7.29) fluid that constitutes 10-30% of the volume of the [[seminal fluid]] that, along with [[spermatozoa]], constitutes [[semen]].  The rest of the seminal fluid is produced by the two [[seminal vesicle]]s. The alkalinity of seminal fluid helps neutralize the acidity of the vaginal tract, prolonging the lifespan of sperm.

The prostate also contains some [[smooth muscle]]s that help expel semen during [[ejaculation]].

==Secretions==
Prostatic secretions vary among species. They are generally composed of simple sugars, and are often slightly [[Base (chemistry)|alkaline]]. 

In human prostatic secretions, the protein content is less than 1% and includes [[proteolytic enzyme]]s, [[acid phosphatase]], and [[prostate-specific antigen]]. The secretions also contain [[zinc]].

==Regulation==
To work properly, the prostate needs male [[hormones]] ([[androgen]]s), which are responsible for male [[sex]] characteristics. 

The main male hormone is [[testosterone]], which is produced mainly by the [[testicle]]s. Some male hormones are produced in small amounts by the [[adrenal gland]]s. However, it is dihydrotestosterone that regulates the prostate.

==Development==
The prostatic part of the urethra develops from the ''pelvic'' (middle) part of the [[urogenital sinus]] (endodermal origin). [[Endodermal]] outgrowths arise from the prostatic part of the urethra and grow into the surrounding [[mesenchyme]]. The glandular epithelium of the prostate differentiates from these endodermal cells, and the associated mesenchyme differentiates into the dense [[stroma]] and the [[smooth muscle]] of the prostate. <ref>Moore and Persaud. Before We Are Born, Essentials of Embryology and Birth Defects, 7th edition. Saunders Elsevier. 2008. ISBN 978-1-4160-3705-7</ref>The prostate glands represent the modified wall of the proximal portion of the male urethra and arises by the 9th week of embryonic life in the [[development of the reproductive system]]. Condensation of [[mesenchyme]], [[urethra]] and [[Wolffian duct]]s gives rise to the adult prostate gland, a composite organ made up of several glandular and non-glandular components tightly fused within a common capsule. 

[[Skene's gland]]s found in many females are [[homology (biology)|homologous]] to the prostate gland in males. 

"In 2002, what was once an obscure female anatomical feature known as the paraurethral glands, or Skene's glands, was officially renamed the prostate by the Federative International Committee on Anatomical Terminology." <ref>Seattle Times - http://seattletimes.nwsource.com/html/health/2002865111_carnalknowledge15.html</ref>

==Structure==
A healthy [[human]] prostate is slightly larger than a [[walnut]]. It surrounds the [[urethra]] just below the [[urinary bladder]] and can be felt during a [[rectal exam]]. 

The ducts are lined with [[transitional epithelium]].

Within the prostate, the urethra coming from the bladder is called the [[prostatic urethra]] and merges with the two [[ejaculatory duct]]s. (The [[male]] urethra has two functions: to carry urine from the bladder during [[urination]] and to carry semen during [[ejaculation]].) The prostate is sheathed in the muscles of the pelvic floor, which contract during the ejaculatory process. 

The prostate can be divided in two different ways: by zone, or by lobe.<ref name="titleInstant Anatomy - Abdomen - Vessels - Veins - Prostatic plexus">{{cite web |url=http://www.instantanatomy.net/abdomen/vessels/vprostaticplexus.html |title=Instant Anatomy - Abdomen - Vessels - Veins - Prostatic plexus |accessdate=2007-11-23 |format= |work=}}</ref>

===Zones===
The "zone" classification is more often used in pathology.

The prostate gland has four distinct glandular regions, two of which arise from different segments of the prostatic urethra:

{| class="wikitable"
| '''Name''' || '''Percent''' || '''Description''' 
 |- 
 | Peripheral zone (PZ) || Composes up to 70% of the normal prostate gland in young men || The sub-capsular portion of the posterior aspect of the prostate gland which surrounds the distal [[urethra]].  It is from this portion of the gland that more than 70% of [[prostatic cancers]] originate.
 |- 
 | Central zone (CZ) || Constitutes approximately 25% of the normal prostate gland || This zone surrounds the [[ejaculatory ducts]]. Central zone tumours account for more than 25% of all prostate cancers. 
 |- 
 | Transition zone (TZ) || Responsible for 5% of the prostate volume || This zone is very rarely associated with carcinoma.  The transition zone surrounds the proximal urethra and is the region of the prostate gland which grows throughout life and is responsible for the disease of [[benign prostatic enlargement]].
 |- 
 | Anterior fibro-muscular zone (or stroma) || Accounts for approximately 5% of the prostatic weight || This zone is usually devoid of glandular components, and composed only, as its name suggests, of [[muscle]] and [[fibrous tissue]].
|}

===Lobes===
[[Image:Prostate middle lobe orig.jpg|right|thumb|Prostate with a large median lobe bulging upwards. A metal instrument is placed in the [[urethra]] which passes through the prostate. This specimen was almost 7 centimeters long with a volume of about 60 [[cubic centimetre]]s on [[transrectal ultrasound]] and was removed during a Hryntschak procedure or transvesical [[prostatectomy]] (removal of the prostate through the bladder) for [[benign prostatic hyperplasia]].]]

The "lobe" classification is more often used in anatomy.

{| class="wikitable"
| Anterior lobe (or isthmus) || roughly corresponds to part of transitional zone
 |- 
 | Posterior lobe || roughly corresponds to peripheral zone 
 |- 
 | Lateral lobes || spans all zones
 |- 
 | Median lobe (or middle lobe) || roughly corresponds to part of central zone
|}

==Prostate disorders==
===Prostatitis===
{{main|Prostatitis}}
[[Prostatitis]] is [[inflammation]] of the prostate gland. There are different forms of prostatitis, each with different causes and outcomes. Acute prostatitis and chronic bacterial prostatitis are treated with [[antibiotics]]; chronic non-bacterial prostatitis or male chronic pelvic pain syndrome, which comprises about 95% of prostatitis diagnoses, is treated by a large variety of modalities including alpha blockers, phytotherapy, physical therapy, psychotherapy, antihistamines, anxiolytics, nerve modulators and more.<ref name="cpcom">{{Cite web|url=http://www.chronicprostatitis.com/meds.html|title=Pharmacological treatment options for prostatitis/chronic pelvic pain syndrome|accessdate=2006-12-11|year=2006}}</ref> More recently, a combination of trigger point and psychological therapy has proved effective as well.<ref name="pmid16952676">{{cite journal |author=Anderson RU, Wise D, Sawyer T, Chan CA |title=Sexual dysfunction in men with chronic prostatitis/chronic pelvic pain syndrome: improvement after trigger point release and paradoxical relaxation training |journal=J. Urol. |volume=176 |issue=4 Pt 1 |pages=1534–8; discussion 1538–9 |year=2006 |pmid=16952676 |doi=10.1016/j.juro.2006.06.010}}</ref>

===Benign prostatic hyperplasia=== 
{{main|Benign prostatic hyperplasia}}
[[Benign prostatic hyperplasia]] (BPH) occurs in older men;<ref name="pmid">{{cite journal |author=Verhamme KM, Dieleman JP, Bleumink GS, ''et al'' |title=Incidence and prevalence of lower urinary tract symptoms suggestive of benign prostatic hyperplasia in primary care--the Triumph project |journal=Eur. Urol. |volume=42 |issue=4 |pages=323–8 |year=2002| doi = 10.1016/S0302-2838(02)00354-8 <!--Retrieved from CrossRef by DOI bot-->}}</ref> the prostate often enlarges to the point where urination becomes difficult. Symptoms include needing to go to the toilet often ([[pollakisuria]]) or taking a while to get started (hesitancy). If the prostate grows too large it may constrict the urethra and impede the flow of urine, making [[urination]] difficult and painful and in extreme cases completely impossible.

BPH can be treated with medication, a [[minimally invasive procedure]] or, in extreme cases, surgery that removes the prostate. Minimally invasive procedures include [[Transurethral needle ablation of the prostate]] (TUNA) and [[Transurethral microwave thermotherapy]] (TUMT). These outpatient procedures may be followed by the insertion of a temporary [[Prostatic stent]], to allow normal voluntary urination, without exacerbating irritative symptoms<ref name="pmid18374395">{{cite journal |author=Dineen MK, Shore ND, Lumerman JH, Saslawsky MJ, Corica AP |title=Use of a Temporary Prostatic Stent After Transurethral Microwave Thermotherapy Reduced Voiding Symptoms and Bother Without Exacerbating Irritative Symptoms. |journal=J. Urol. |volume=71 |issue=5 |pages=873–877 |year=2008 |pmid=18374395 |doi=10.1016/j.urology.2007.12.015}}</ref>.

The surgery most often used in such cases is called transurethral resection of the prostate (TURP or TUR). In TURP, an instrument is inserted through the urethra to remove prostate tissue that is pressing against the upper part of the urethra and restricting the flow of urine. Older men often have ''corpora amylacea''<ref>{{cite web |url=http://w3.ouhsc.edu/histology/Glass%20slides/33_09.jpg |title=Slide 33: Prostate, at ouhsc.edu |accessdate= |format= |work=}}</ref> ([[amyloid]]), dense accumulations of calcified proteinaceous material, in the ducts of their prostates. The corpora amylacea may obstruct the lumens of the prostatic ducts, and may underlie some cases of BPH.

Urinary frequency due to bladder spasm, common in older men, may be confused with prostatic hyperplasia. 
[[Epidemiology|Statistical observations]] suggest that a diet low in [[dietary fat|fat]] and [[red meat]] and high in [[protein]] and [[vegetables]], as well as regular [[alcohol consumption]], could protect against BPH.<ref name="pmid18263602">{{cite journal |author=Kristal AR, Arnold KB, Schenk JM, ''et al'' |title=Dietary patterns, supplement use, and the risk of symptomatic benign prostatic hyperplasia: results from the prostate cancer prevention trial |journal=Am. J. Epidemiol. |volume=167 |issue=8 |pages=925–34 |year=2008 |month=April |pmid=18263602 |doi=10.1093/aje/kwm389 |url=http://aje.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=18263602}}</ref>

===Prostate cancer===
{{main|Prostate cancer}}
[[Prostate cancer]] is one of the most common [[cancer]]s affecting older men in [[developed countries]] and a significant cause of [[death]] for elderly men (estimated by some specialists at 3%). Regular [[rectal exam]]s are recommended for older men to detect prostate cancer early.

Though prostate cancer is of most concern to older men, it is like other cancers, a complex disease with many risk factors; race, age, genetics, and lifestyle habits can all contribute to its development.<ref>Nutritional Prevention of Prostate Cancer, available online at [http://www.preventprostatecancer.info]. (Purchase required)</ref>

==Male sexual response==
During orgasm sperm are transmitted from the ductus deferens into the male urethra via the ejaculatory ducts, which lie within the prostate gland. The prostate is often referred to as the "male [[G-spot]]". Some men are able to achieve [[orgasm]] solely through stimulation of the prostate gland, such as [[prostate massage]] or receptive [[anal intercourse]].  Men who report the sensation of prostate stimulation often give descriptions similar to women's accounts of [[G-spot]] stimulation.<ref name=Ladas>{{cite book |last=Ladas |first=AK |coauthors=Whipple, B; Perry, JD |title=The G spot and other discoveries about human sexuality |origyear=1982 |publisher=Holt, Rinehart, and Winston |location=New York}}</ref>

==Vasectomy and risk of prostate cancer==
In 1993, the Journal of the American Medical Association revealed a connection between [[vasectomy]] and an increased risk of prostate cancer. Reported studies of 48,000 and 29,000 men who had vasectomies showed 66 percent and 56 percent higher rates of prostate cancer, respectively. The risk increased with age and the number of years since the vasectomy was performed. 

However, in March of the same year, the National Institute of Child Health and Human Development held a conference cosponsored by the National Cancer Institute and others to review the available data and information on the link between prostate cancer and vasectomies.  It was determined that an association between the two was very weak at best, and even if having a vasectomy increased one's risk, the risk was relatively small. 

In 1997, the NCI held a conference with the prostate cancer Progressive Review Group (a committee of scientists, medical personnel, and others).  Their final report, published in 1998 stated that evidence that vasectomies help to develop prostate cancer was weak at best.<ref>{{cite web |title=Vasectomy and Cancer Risk
 |url=http://www.cancer.gov/cancertopics/factsheet/Risk/vasectomy |date=06/24/2003 |publisher=National Cancer Institute |accessdate=2008-01-08}}</ref>

==Stenting the prostate==
Recent scientific breakthroughs have now meant using a [[Prostatic stent]] is a viable method of dis-obstructing the prostate. Stents are devices inserted into the urethra to widen it and keep it open. Stents can be temporary or permanent and is mostly done on an outpatient basis under local or spinal anesthesia and usually takes about 30 minutes.

==Additional images==
<gallery>
 Image:Illu bladder.jpg|Urinary bladder
 Image:Illu penis.jpg|Structure of the penis
 Image:Illu prostate lobes.jpg|Lobes of prostate
 Image:Illu prostate zones.jpg|Zones of prostate
 Image:Illu quiz prostate01.jpg|Prostate
 Image:Prostatehistology.jpg|'''Prostate under a microscope''' This image shows the microscopic glands of the prostate
 Image:male anatomy.png|Male Anatomy
 Image:Gray543.png|The deeper branches of the internal pudendal artery.
 Image:Gray619.png|Lymphatics of the prostate. 
 Image:Gray1152.png|Fundus of the bladder with the vesiculæ seminales.
 Image:Gray1153.png|Vesiculae seminales and ampullae of ductus deferentes, seen from the front. 
 Image:Gray1156.png|Vertical section of bladder, penis, and urethra.
</gallery>

==References==
The text of this article was originally taken from NIH Publication No. 02-4806, a public domain resource [http://web.archive.org/web/20020601194638/http://www.niddk.nih.gov/health/urolog/pubs/prospro/prospro.htm#1].
{{reflist|2}}

==External links==
* [http://kidney.niddk.nih.gov/kudiseases/pubs/prostate_ez/index.htm "What I need to know about prostate problems" by the US National Institutes of Health.]


{{Male reproductive system}}

[[Category:Glands]]
[[Category:Exocrine system]]
[[Category:Male Genitalia]]

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