See soorce fer Testicle

===Internal structur===
[[Image:transversetestis.png|thumb|right|Transverse section throu the left side o the scrotum an the left testis.]]

====Duct seestem====
The testes are kivert bi a teuch membranous shell cried the [[tunica albuginea (testicles)|tunica albuginea]]. Within the testes are verra fine coiled tubes cried [[seminiferous tubules]]. The tubules are lined wi a layer o cells ([[germ cells]]) that develop frae [[puberty]] throu auld age intae [[sperm]] [[cell (biology)|cells]] (kent as [[spermatozoa]] or male [[gametes]] forby). The developin sperm travel throu the seminiferous tubules tae the [[rete testis]] locatit in the [[mediastinum testis]], tae the [[efferent ducts]], an then tae the [[epididymis]] whaur newly creatit sperm cells matur (see [[spermatogenesis]]). The sperm muive intae the [[vas deferens]], an are eventually expelled throu the [[urethra]] an oot o the [[Freemit urethral orifice (male)|urethral orifice]] throu muscular contractions.

====Primary cell teeps====
;Within the [[seminiferous tubules]]:
* Here, [[germ cells]] develop intae [[spermatogonia]], [[spermatocytes]], [[spermatids]] an [[spermatozoon]] throu the process o spermatogenesis. The gametes conteen DNA for fertilisation o an ovum<ref>[https://books.google.com/books?id=FoSiGTXn6BUC&printsec=frontcover#v=onepage&q=testes%20OR%20testis%20OR%20testicle%20OR%20testicles&f=false Histology, A Text and Atlas] by Michael H. Ross and Wojciech Pawlina, Lippincott Williams & Wilkins, 5th ed, 2006</ref>
* [[Sertoli cells]] – the true epithelium o the seminiferous epithelium, creetical for the support o germ cell development intae spermatozoa.  Sertoli cells secrete [[inhibin]].<ref>{{cite journal |vauthors=Skinner M, McLachlan R, Bremner W |title=Stimulation of Sertoli cell inhibin secretion by the testicular paracrine factor PModS |journal=Mol Cell Endocrinol |volume=66 |issue=2 |pages=239–49 |year=1989 |pmid=2515083 |doi=10.1016/0303-7207(89)90036-1}}</ref>
* [[Peritubular myoid cells|Peritubular]] [[myoid cells]] surroond the seminiferous tubules.<ref>Arch Histol Cytol. 1996 Mar;59(1):1–13</ref>

;Atween tubules (intersteetial cells)
* [[Leydig cells]] – cells localized atween [[seminiferous tubules]] that produce an secrete [[testosterone]] an ither [[androgen]]s important for [[sexual development]] an [[puberty]], [[seicontar sexual chairacteristics]] lik facial hair, [[Human sexual activity|sexual behaviour]] an [[libido]], supportin spermatogenesis an [[erection|erectile function]]. Testosterone controls testicular vollum forby.
* Present as weel are:
** Immatur Leydig cells
** Intersteetial [[macrophages]] an [[epithelial cells]].

====Bluid supplee an lymphatic drainage====
Bluid supplee an [[lymphatic drainage]] o the testes an scrotum are distinct:
* The paired [[testicular arteries]] arise directly frae the [[abdominal aorta]] an strynd throu the [[inguinal canal]], while the scrotum an the rest o the freemit genitalia is supplee'd bi the [[internal pudendal artery]] (itsel a branch o the [[internal iliac artery]]).
* The testis haes collateral bluid supply frae 1. the [[cremasteric artery]] (a brainch o the [[inferior epigastric artery]], that is a branch o the [[external iliac artery]]), an 2. the [[artery tae the ductus deferens]] (a brainch o the [[inferior vesical artery]], that is a brainch o the [[internal iliac artery]]). Tharefore, if the testicular artery is ligatit, e.g., in a Fowler-Stevens [[orchiopexy]] for a heich undescendit testis, the testis will uisually survive on thir ither bluid supplies.
* Lymphatic drainage o the testes follaes the testicular arteries back tae the [[paraaortic lymph nodes]], while lymph frae the scrotum drains tae the [[inguinal lymph nodes]].

====Layers====
Mony anatomical featurs o the adult testis reflect its developmental oreegin in the [[abdomen]]. The layers o tishie enclosin ilk testicle are derived frae the layers o the anterior [[abdominal waw]]. Notably, the [[cremasteric muscle]] arises frae the [[internal oblique muscle]].

====The bluid–testis barrier====
Muckle molecules canna pass frae the bluid intae the lumen o a seminiferous tubule due tae the presence o [[ticht junctions]] atween adjacent [[Sertoli cells]]. The spermatogonia are in the basal compartment (deep tae the level o the ticht junctions) an the mair matur forms such as primar an seicontar spermatocytes an spermatids are in the adluminal compairtment.

The function o the [[bluid–testis baurier]] (reid heichlicht in diagram abuin) mey be tae prevent an [[auto-immune]] reaction. Matur sperm (an thair [[antigen]]s) arise lang efter immune tolerance is established in infancy. Tharefore, syne sperm are antigenically different frae ''sel'' tishie, a male ainimal can react immunologically tae his awn sperm. In fact, he is capable o makkin antibouks against them.

Injection o sperm antigens causes inflammation o the testis (auto-immune orchitis) an reduced fertility. Sicweys, the bluid–testis baurier mey reduce the likeliheid that sperm proteins will induce an immune response, reducin fertility an sae progeny.