Editing Prostate (section)

==Structure==
The prostate is a [[exocrine gland]] of the [[male reproductive system]]. In adults, it is about the size of a [[walnut]],<ref name="Young-2013">{{Cite book |last1=Young |first1=Barbara |title=Wheater's functional histology: a text and colour atlas. |last2=O'Dowd |first2=Geraldine |last3=Woodford |first3=Phillip |date=2013 |publisher=Elsevier |isbn=9780702047473 |edition=6th |location=Philadelphia |pages=347–8}}</ref> and has an average weight of about {{convert|11|g}}, usually ranging between {{convert|7|and(-)|16|g}}.<ref>{{Cite journal |vauthors=Leissner KH, Tisell LE |year=1979 |title=The weight of the human prostate |journal=Scand. J. Urol. Nephrol. |volume=13 |issue=2 |pages=137–42 |doi=10.3109/00365597909181168 |pmid=90380}}</ref> The prostate is located in the pelvis. It sits below the [[urinary bladder]] and surrounds the [[urethra]]. The part of the urethra passing through it is called the [[prostatic urethra]], which joins with the two [[ejaculatory duct]]s.<ref name="Young-2013" /> The prostate is covered in a surface called the ''prostatic capsule'' or ''prostatic fascia''.<ref name="Standring-2016" />

The internal structure of the prostate has been described using both lobes and zones.<ref name="Goddard-2019">{{Cite journal |last=Goddard |first=Jonathan Charles |date=January 2019 |title=The history of the prostate, part one: say what you see |journal=Trends in Urology & Men's Health |language=en |volume=10 |issue=1 |pages=28–30 |doi=10.1002/tre.676 |doi-access=free}}</ref><ref name="Young-2013" /> Because of the variation in descriptions and definitions of lobes, the zone classification is used more predominantly.<ref name="Young-2013" />

The prostate has been described as consisting of three or four zones.<ref name="Young-2013" /><ref name="Standring-2016">{{Cite book |title=Gray's anatomy : the anatomical basis of clinical practice |year=2016 |isbn=9780702052309 |editor-last=Standring, Susan |edition=41st |location=Philadelphia |pages=1266–1270 |chapter=Prostate |oclc=920806541}}</ref> Zones are more typically able to be seen on [[histology]], or in [[medical imaging]], such as [[ultrasound]] or [[Magnetic resonance imaging|MRI]].<ref name="Young-2013" /><ref name="Goddard-2019" />

{| class="wikitable plainrowheaders"
|-
! scope="col" | Name
! scope="col" | Fraction of adult gland<ref name="Young-2013" />
! scope="col" | Description
|-
! scope="row" | Peripheral zone (PZ)
| style="text-align: center;" | 70%
| The back of the gland that surrounds the distal urethra and lies beneath the capsule. About 70–80% of [[prostatic cancers]] originate from this zone of the gland.<ref name="Urology Match">[http://www.urologymatch.com/ProstateAnatomy.htm "Basic Principles: Prostate Anatomy"] {{Webarchive|url=https://web.archive.org/web/20101015014554/http://www.urologymatch.com/ProstateAnatomy.htm |date=2010-10-15 }}. Urology Match. Www.urologymatch.com. Web. 14 June 2010.</ref><ref name="PCTG">[http://www.prostate-cancer.com/prostate-cancer-treatment-overview/overview-prostate-anatomy.html "Prostate Cancer Information from the Foundation of the Prostate Gland."] Prostate Cancer Treatment Guide. Web. 14 June 2010.</ref>
|-
! scope="row" | Central zone (CZ)
| style="text-align: center;" | 20%
| This zone surrounds the ejaculatory ducts.<ref name="Young-2013" /> The central zone accounts for roughly 2.5% of prostate cancers; these cancers tend to be more aggressive and more likely to invade the seminal vesicles.<ref>{{Cite journal |vauthors=Cohen RJ, Shannon BA, Phillips M, Moorin RE, Wheeler TM, Garrett KL |year=2008 |title=Central zone carcinoma of the prostate gland: a distinct tumor type with poor prognostic features |journal=The Journal of Urology |volume=179 |issue=5 |pages=1762–7; discussion 1767 |doi=10.1016/j.juro.2008.01.017 |pmid=18343454 |s2cid=52417682}}</ref>
|-
! scope="row" | Transition zone (TZ)
| style="text-align: center;" | 5%
| The transition zone surrounds the proximal urethra.<ref name="Young-2013" /> ~10–20% of prostate cancers originate in this zone. It is the region of the prostate gland that grows throughout life and causes the disease of [[benign prostatic enlargement]].<ref name="Urology Match" /><ref name="PCTG" />
|-
! scope="row" | Anterior fibro-muscular zone (or [[stroma (animal tissue)|stroma]])
| {{N/A}}
| This area, not always considered a zone,<ref name="Standring-2016" /> is usually devoid of glandular components and composed only, as its name suggests, of [[muscle]] and [[fibrous tissue]].<ref name="Young-2013" />
|}

The "lobe" classification describes lobes that, while originally defined in the fetus, are also visible in gross anatomy, including dissection and when viewed endoscopically.<ref name="Goddard-2019" /><ref name="Standring-2016" /> The five lobes are the anterior lobe or isthmus, the posterior lobe, the right and left lateral lobes, and the middle or median lobe.

<gallery mode="packed" heights="175px">
File:Illu prostate lobes.jpg|Lobes of prostate
File:Prostate zones.png|Zones of prostate
</gallery>

Inside of the prostate, adjacent and parallel to the prostatic urethra, there are two longitudinal muscle systems. On the front side ([[Anatomical terms of location#Dorsal and ventral|ventrally]]) runs the urethral [[dilator]] (''musculus dilatator urethrae''), on the backside ([[Anatomical terms of location#Dorsal and ventral|dorsally]]) runs the muscle switching the urethra into the ejaculatory state (''musculus ejaculatorius'').<ref name="Schünke-2012">Michael Schünke, Erik Schulte, Udo Schumacher: ''PROMETHEUS Innere Organe. LernAtlas Anatomie'', vol 2: ''Innere Organe'', Thieme Verlag, Stuttgart/Germany 2012, {{ISBN|9783131395337}}, p. 298, [https://www.wissenschaft-shop.de/out/media/docs/700380-innere-organe-musterseiten.pdf PDF].</ref>

===Blood and lymphatic vessels===
The prostate receives blood through the [[inferior vesical artery]], [[internal pudendal artery]], and [[middle rectal arteries]]. These vessels enter the prostate on its outer {{wt|en|posterior}} surface where it meets the bladder, and travel forward to the apex of the prostate.<ref name="Standring-2016" /> Both the inferior vesical and the middle rectal arteries often arise together directly from the [[internal iliac arteries]]. On entering the bladder, the inferior vesical artery splits into a urethral branch, supplying the urethral prostate; and a capsular branch, which travels around the capsule and has smaller branches, which perforate into the prostate.<ref name="Standring-2016" />

The veins of the prostate form a network – the [[prostatic venous plexus]], primarily around its front and outer surface.<ref name="Standring-2016" /> This network also receives blood from the [[deep dorsal vein of the penis]], and is connected via branches to the [[Vesical venous plexus|vesical plexus]] and [[internal pudendal veins]].<ref name="Standring-2016" /> Veins drain into the [[Vesical veins|vesical]] and then [[internal iliac vein]]s.<ref name="Standring-2016" />

The lymphatic drainage of the prostate depends on the positioning of the area. Vessels surrounding the [[vas deferens]], some of the vessels in the seminal vesicle, and a vessel from the posterior surface of the prostate drain into the [[external iliac lymph nodes]].<ref name="Standring-2016" /> Some of the seminal vesicle vessels, prostatic vessels, and vessels from the anterior prostate drain into [[internal iliac lymph nodes]].<ref name="Standring-2016" /> Vessels of the prostate itself also drain into the [[Obturator lymph nodes|obturator]] and [[sacral lymph nodes]].<ref name="Standring-2016" />

<gallery mode="packed" heights="175px">
File:Internal_iliac_branches.PNG|Imaging showing the [[inferior vesical artery|inferior vesical]], [[internal pudendal artery|inferior pudendal]] and [[middle rectal arteries]] arising from the [[internal iliac arteries]].
File:Gray611.png|Image showing the [[external iliac lymph nodes]] and their positions around the external iliac artery and [[external iliac veins|vein]]
</gallery>

===Microanatomy===
[[File:Corpora amylacea intermed mag.jpg|thumb|right|[[Micrograph]] of benign prostatic glands with [[corpora amylacea]]. [[H&E stain]].]]

The prostate consists of glandular and [[connective tissue]].<ref name="Young-2013" /> Tall [[Columnar cell|column-shaped cells]] form the lining (the [[epithelium]]) of the glands.<ref name="Young-2013" /> These form one layer or may be [[Pseudostratified epithelium|pseudostratified]].<ref name="Standring-2016" /> The epithelium is highly variable and areas of low [[Cuboidal epithelia|cuboidal]] or [[squamous epithelium|flat]] cells can also be present, with transitional epithelium in the outer regions of the longer ducts.<ref>{{Cite web |title=Prostate Gland Development |url=http://www.ana.ed.ac.uk/database/prosbase/prosdev.html |archive-url=https://web.archive.org/web/20030430000050/http://www.ana.ed.ac.uk/database/prosbase/prosdev.html |archive-date=2003-04-30 |access-date=2011-08-03 |website=ana.ed.ac.uk}}</ref> [[Basal cell]]s surround the luminal epithelial cells in benign glands. The glands are formed as many follicles, which drain into canals and subsequently 12–20 main ducts, These in turn drain into the urethra as it passes through the prostate.<ref name="Standring-2016" /> There are also a small amount of flat cells, which sit next to the basement membranes of glands, and act as stem cells.<ref name="Young-2013" />

The connective tissue of the prostate is made up of fibrous tissue and [[smooth muscle]].<ref name="Young-2013" /> The fibrous tissue separates the gland into lobules.<ref name="Young-2013" /> It also sits between the glands and is composed of randomly orientated smooth-muscle bundles that are continuous with the bladder.<ref>{{Cite web |title=Prostate |url=https://webpath.med.utah.edu/TUTORIAL/PROSTATE/PROSTATE.html |access-date=2019-11-17 |website=webpath.med.utah.edu}}</ref>

Over time, thickened secretions called [[corpora amylacea]] accumulate in the gland.<ref name="Young-2013" />

<gallery mode="packed">
File:Prostatehistology.jpg|Microscopic glands of the prostate
File:Prostate gland microanatomy.png|Microanatomy of a prostatic gland, showing both luminal cells and surrounding basal cells. H&E stain.
File:Histology of normal prostate.jpg|Histology of normal prostate, H&E stain, with benign features: Glands are rounded to irregularly branching, with an inner layer of epithelial cells surrounded by an outer layer of basal cells. They are surrounded by ample stroma.
File:Histology of prostate atrophy.jpg|Histology of prostate with gradually increasing simple atrophy from left to right, H&E stain. Crowding and angulation may mimic that of adenocarcinoma, but there is nuclear basophilia rather than atypia, and occasional basal cells can still be seen.
</gallery>

===Gene and protein expression===
{{Further|Bioinformatics#Gene and protein expression}}

About 20,000 [[protein-coding genes]] are expressed in human cells and almost 75% of these genes are expressed in the normal prostate.<ref>{{Cite web |title=The human proteome in prostate – The Human Protein Atlas |url=https://www.proteinatlas.org/humanproteome/prostate |access-date=2017-09-26 |website=www.proteinatlas.org}}</ref><ref>{{Cite journal |last1=Uhlén |first1=Mathias |last2=Fagerberg |first2=Linn |last3=Hallström |first3=Björn M. |last4=Lindskog |first4=Cecilia |last5=Oksvold |first5=Per |last6=Mardinoglu |first6=Adil |last7=Sivertsson |first7=Åsa |last8=Kampf |first8=Caroline |last9=Sjöstedt |first9=Evelina |date=2015-01-23 |title=Tissue-based map of the human proteome |journal=Science |volume=347 |issue=6220 |pages=1260419 |doi=10.1126/science.1260419 |issn=0036-8075 |pmid=25613900 |s2cid=802377}}</ref> About 150 of these genes are more specifically expressed in the prostate, with about 20 genes being highly prostate specific.<ref>{{Cite journal |last1=O'Hurley |first1=Gillian |last2=Busch |first2=Christer |last3=Fagerberg |first3=Linn |last4=Hallström |first4=Björn M. |last5=Stadler |first5=Charlotte |last6=Tolf |first6=Anna |last7=Lundberg |first7=Emma |last8=Schwenk |first8=Jochen M. |last9=Jirström |first9=Karin |date=2015-08-03 |title=Analysis of the Human Prostate-Specific Proteome Defined by Transcriptomics and Antibody-Based Profiling Identifies TMEM79 and ACOXL as Two Putative, Diagnostic Markers in Prostate Cancer |journal=PLOS ONE |volume=10 |issue=8 |pages=e0133449 |bibcode=2015PLoSO..1033449O |doi=10.1371/journal.pone.0133449 |issn=1932-6203 |pmc=4523174 |pmid=26237329 |doi-access=free}}</ref> The corresponding specific proteins are expressed in the glandular and secretory cells of the prostatic gland and have functions that are important for the characteristics of [[semen]], including prostate-specific [[protein]]s, such as the [[Prostate-specific antigen|prostate specific antigen (PSA)]], and the [[prostatic acid phosphatase]].<ref>{{Cite journal |last1=Kong |first1=HY |last2=Byun |first2=J |date=January 2013 |title=Emerging roles of human prostatic Acid phosphatase. |journal=Biomolecules & Therapeutics |volume=21 |issue=1 |pages=10–20 |doi=10.4062/biomolther.2012.095 |pmc=3762301 |pmid=24009853 |doi-access=free}}</ref>

===Development===
{{Further|Development of the reproductive system}}

In the developing [[embryo]], at the hind end lies an inpouching called the [[Cloaca (embryology)|cloaca]]. This, over the fourth to the seventh week, divides into a [[urogenital sinus]] and the beginnings of the [[anal canal]], with a wall forming between these two inpouchings called the [[urorectal septum]].<ref name="Sadley-2019">{{Cite book |last=Sadley |first=TW |title=Langman's medical embryology |date=2019 |publisher=Wolters Kluwer |isbn=9781496383907 |edition=14th |location=Philadelphia |pages=263–66 |chapter=Bladder and urethra}}</ref> The urogenital sinus divides into three parts, with the middle part forming the urethra; the upper part is largest and becomes the [[urinary bladder]], and the lower part then changes depending on the biological sex of the embryo.<ref name="Sadley-2019" />

The prostatic part of the urethra develops from the middle, pelvic, part of the urogenital sinus, which is of [[endoderm]]al origin.<ref name="Sadley-2019a">{{Cite book |last=Sadley |first=TW |title=Langman's medical embryology |date=2019 |publisher=Wolters Kluwer |isbn=9781496383907 |edition=14th |location=Philadelphia |pages=265–6}}</ref> Around the end of the third month of embryonic life, outgrowths arise from the prostatic part of the urethra and grow into the surrounding [[mesenchyme]].<ref name="Sadley-2019a" /> The cells lining this part of the urethra differentiate into the glandular epithelium of the prostate.<ref name="Sadley-2019a" /> The associated mesenchyme differentiates into the dense connective tissue and the [[Smooth muscle tissue|smooth muscle]] of the prostate.<ref>{{Cite book |last1=Moore |first1=Keith L. |title=Before We are Born: Essentials of Embryology and Birth Defects |last2=Persaud |first2=T. V. N. |last3=Torchia |first3=Mark G. |publisher=Saunders/Elsevier |year=2008 |isbn=978-1-4160-3705-7 |edition=7th}}</ref>

Condensation of [[mesenchyme]], [[urethra]], and [[Wolffian duct]]s gives rise to the adult prostate gland, a composite organ made up of several tightly fused glandular and non-glandular components. To function 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. It is [[dihydrotestosterone]] (DHT), a metabolite of testosterone, that predominantly regulates the prostate. The prostate gland enlarges over time, until the fourth decade of life.<ref name="Standring-2016" />