Embryology And Surgical Anatomy Of Testis And Scrotum – Overview

Testicular Embryology

  • Initially the gonads are similar in both sexes
  • Developed from the (mesoderm) mesonephric / wolffian ducts

SRY gene on the Y chromosome

                  
Activation of testicular determining factor and series of hormones
                 
Wolffian duct starts to differentiate at 7 weeks of gestation
                  
Gonads are converted into testis


Descent Of The Testis
  • Until the end of fetal life, the testes are located within the abdominal cavity
  • Testes are initially located extraperitoneally on the posterior abdominal wall at the level of lumber 2 vertebrae
  • Descent of the testis is highly influenced by gubernaculum testis.
  • Gubenaculum testis is also an extra-peritoneal structure which passes caudally to the inguinal regions and through the inguinal canal, down to the superficial skin 
  • Gubernaculum testis is two attachments
    • One end is attached to the inferior aspect of the testis
    • Other end is attach to the genital swelling (Future scrotum)


As the fetus grows the gubernaculum testis become progressively shorter

                  
Because of the attachment with the inferior testis, the testis and processus vaginalis (Peritoneum of the anterior abdominal wall) is dragged along with it
                  
Processus vaginalis helps the testis to slide through the inguinal canal
                  
Ultimately the testes drops into the scrotum at (Near birth or soon after birth)
                  
Processus vaginalis usually closes after birth

Descent of testis



Anatomy Of The Spermatic Cord

  • Formed by vas deferens
  • Covering of spermatic cord
    • Internal spermatic fasica – Originates from transversalis fascia 
    • Cremasteric fascia – Originates from fascial coverings of internal oblique
    • External spermatic fascia – Originates from external oblique aponeurosis
 
  • Contents of the cord
    • Vas deferens
    • Arteries
      • Testicular artery
      • Artery of vas deferens 
      • Cremasteric artery 
    • Veins
      • Pampiniform plexus
      • Testicular, Cremasteric, Deferential veins 
    • Nerves
      • Genital branch of the genitofemoral nerve
      • Parasympathetic and sympathetic nerves
    • Lymphatics


Anatomy Of Scrotum
  • It protects and facilitates temperature regulation of the testes to ensure optimal spermatogenesis
  • Formed by the fusion of the left and right labioscrotal folds, and has a septum that separates the two halves
  • Right testicle lies at a higher level than the left testicle
  • Layers of the scrotum
    • Skin
    • Dartos muscle
    • External spermatic fascia 
    • Cremaster muscle
    • Internal spermatic fascia
    • Tunica vaginalis

  • Blood supply 
    • Anterior and posterior scrotal arteries
  • Lymphatic drainage 
    • To inguinal lymph nodes 
 

Anatomy Of Epididymis
  • Consist of three parts
    • Head, body and tail
  • Only the epididymal head is fixed to the upper part of the testis, 
  • Blood and nerve supply for the epididymis and testis are generally found on the posterior aspect 
  • Blood supply – By testicular arteries – Branch of abdominal aorta  
 
 
 

Anatomy Of The Testis

  • Testis is surrounded by tunica vaginalis – Closed sac of parietal peritoneum
  • Testicular parenchyma is protected by the tunica albuginea
  • Blood supply
    • Arterial supply
      • Testicular arteries – Branch of abdominal aorta 
      • Cremasteric artery – Branch of inferior epigastric artery
      • Artery of the vas deferens
    • Venous drainage 
      • Pampiniform plexus
        • Right testicular vein – Drains into inferior vena cava
        • Left testicular vein – Drains into left renal vein, then into the inferior vena cava
  • Lymphatic drainage
    • To para-aortic lymph nodes
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