Reproductive and Genitourinary System PDF

Testes The testes and epididymis are paired structures, located within the scrotum. The testes are the site of sperm production and hormone synthesis, while the epididymis has a role in the storage of sperm Position Suspended from the abdomen by the spermatic cord due to descent through...

Testes The testes and epididymis are paired structures, located within the scrotum. The testes are the site of sperm production and hormone synthesis, while the epididymis has a role in the storage of sperm Position Suspended from the abdomen by the spermatic cord due to descent through the inguinal canal during development Epididymis Head = formed from efferent tubules of tests Body = heavily coiled duct of epididymis Tail = origin of vas deferens Testes Neurovasculature Arterial supply = testicular arteries (arise from abdominal aorta) ○ Anastomoses with cremasteric artery (branch of inferior epigastric) and artery of vas deferens (branch of inferior vesical artery) Venous drainage = pampiniform plexus → testicular veins ○ Left testicular vein → left renal vein ○ Right testicular vein → IVC Lymphatic drainage = lumbar and para-aortic lymph nodes Innervation= testicular plexus (ANS and sensory) - derived from renal and aortic plexus Testis Each testis consists of highly-coiled seminiferous tubules and interstitium The testis have an optimal temperature of 34°C which is maintained by a range of factors: ○ Embryological descent of the testes via the inguinal canal before birth from the abdomen ○ Cremaster muscle (skeletal muscle) which raises the testes in response to cold, sex or fear ○ Dartos muscle (smooth muscle) which changes the surface area of the scrotum to regulate temperature → wrinkling of the testicles ○ Pampiniform plexus of testicular veins Functions ○ Spermatogenesis ○ Androgen (testosterone) production Histology of the Testis The testes are composed of highly-coiled seminiferous tubules and the interstitial space which resides in between these tubules. Seminiferous tubules = complex stratified epithelium (cuboidal cells which can adjust to stretching and recoiling Germ cells The seminiferous epithelium contains migrating germ line stem cells which become spermatids (via spermatogenesis) and spermatozoa (via spermiogenesis) Spermatozoa are released into the fluid filled lumen This maturation process is supported by Sertoli cells Peritubular myoid Thin, contractile cells which line the external tubule cells Functions ○ Propel spermatozoa towards vas deferens ○ Structural support Histology of the Testis Sertoli cells Tree-shaped columnar cells with a tall cytoplasm - extend from the basal lamina to the lumen Respond to FSH in order to execute functions Functions ○ Sex determination - expression of SRY gene (sex-determining factor on Y chromosome) during embryonic development to initiate male sex determination ○ Developmental - production of Anti-Mullerian Hormone (AMH) during early foetal life which causes regression of female internal organs ○ Hormonal regulation - release of inhibins and activins to regulate FSH secretion ○ Stem cell regulation - release of GDNF to ensure self-renewal of spermatogonial stem cells ○ Spermatogenesis - support spermatogenesis by responding to FSH and testosterone ○ Forms the blood-testis barrier via tight junctions, desmosomes and gap junctions to protect immature sperm from the immune system Histology of the Testis Interstitial space Primary component is Leydig cells ○ Primary source of testosterone ○ Produce testosterone in response to luteinising hormone (LH) from the pituitary gland ○ Testosterone produced will either: Diffuse into the seminiferous tubules Enter the peripheral circulation to drive male reproductive development ○ Contain Crystals of Reinke - rod shaped structures ○ Abundant SER - for testosterone production Layers of the Testis Tunica vaginalis (most superficial) ○ 2 layers of the tunica vaginalis Parietal layer lines the scrotal cavity Visceral layer overlays the tunica albuginea ○ Separated by a thin layer of fluid to reduce friction Increased fluid in this space → hydrocele Tunica albuginea ○ Connects with the fibrous layer of the surrounding epididymis ○ Divides the testes into lobules – forms septa between each lobules Meeting point of septa = mediastinum Tunica vasculosa ○ Innermost layer ○ Consists of rich vascular supply and connective tissue Descent of the Testes Originates and descend from the abdomen during gestation Hence why they drain to para-aortic lymph nodes as opposed to the scrotum which drains to superficial inguinal lymph nodes An evagination of the peritoneum (processus vaginalis) descending with the transversalis and internal oblique m. ○ Transversalis m. fascia → internal spermatic fascia ○ Internal oblique m. fascia + Transversalis m. → cremaster m. ○ Aponeurosis of external oblique m. → external spermatic fascia The gubernaculum is attached to the testis and as it shortens, causing testicular descent