Male genitals

Penis

To follow

Scrotum

• Pouch of skin containing the testes and spermatic cords
• Superficial fascia is continuous with superficial abdominal fascia (Colles fascia), so blood can drain down into scrotum
  • Superficial fascia contains muscle fibres - dartos - but no fat
  • Dartos innervated by SNS fibres along with genital branch of genitofemoral nerve
• Scrotal septum divides scrotum down the midline - midline raphe is the surface marking
• Blood supply
  • Superficial and deep external pudendal arteries
  • Posteriorly some branches from internal pudendal
• Innervation
  • Ilioinguinal nerve to anterior third of scrotal skin
  • Posterior scrotal branches of the perineal nerves (S2-4) and the perineal branch of the posterior cutaneous nerve of the thigh to the posterior two-thirds of the scrotal skin
• Lymphatics
  • To superficial inguinal nodes

Testes

• Embryology
  • Develop in retroperitoneum below the kidneys at week 7, initially with mesonephric duct (Wolffian duct - see kidney embryology) attached
    • Paramesonephric (Mullerian) duct forms appendix testis and prostatic utricle in men
  • Gubernaculum forms between testis and abdominal wall muscles
  • Processus vaginalis forms in the abdominal wall as an evagination
    • Fibres of the internal oblique become cremasteric fibres
    • Fibres of EO become external spermatic fascia
  • 3 months gestation: testes lie at internal ring
  • 7-9 months gestation: descent to scrotum, accompanied by shortening of gubernaculum, pushing fascial structures ahead of it
  • A peritoneal evagination covers the testis, called processus vaginalis, which is usually obliterated during first year of life (except around the testis where it persists as a double layer (tunica vaginalis) which permits movement)
    • The connection to peritoneal cavity is thus removed - if it persists, the boy will have a hernia or congenital hydrocoele (see separate topic)
• Coverings (Some Days Eddie Can Irritate People Very Thoroughly)
  • Skin
  • Dartos
  • External spermatic fascia
  • Cremasteric fascia (no muscle at this level)
  • Internal spermatic fascia
  • Tunica vaginalis (anterior and lateral - residual peritoneum)
  • Tunica vasculosa (filmy coat with blood vessels)
  • Tunica albuginea (dense, whitish-blue coat)
    • Thickest posteriorly, where it penetrates into testis as mediastinum testis
• Arterial supply
  • Testicular arteries originate high up in retroperitoneum from just below renal arteries (predominant supply)
  • Anastomosis with deferential artery and cremasteric artery lower down in cord - it is therefore uncommon for significant ischaemia of the testis to occur with division of the testicular artery within the peritoneal cavity, although will usually get some degree of atrophy
• Venous
  • Testis and epididymis drain into a plexus, which lies mainly anterior to vas. Ascend in the cord as ~2 veins, then enter abdomen as one or two veins.
  • Testicular veins drain into renal vein on left and IVC on right
  • Can get varicocoele, especially on left - see separate topic
• Lymphatics
  • Lymphatic drainage also follows this route to para-aortic nodes

Epididymis

• Lies on posterior aspect of testis
• Head (upper part) connects with seminiferous tubules
• Body
• Tail (lower) connects with vas deferens