Scrotum & Testis

Testis & Coverings (360-362) (370 in 3rd)

2.5x3x5cm average.

Testis pushes abdominal wall in its descent, invaginating peritoneum in front (processus vaginalis).  Remnant = tunica vaginalis anteriorly & laterally (this covers sinus of epididymis Pl362 lower)

Tunica albuginea = dense coat covering testis; thickest posteriorly (invaginates as mediastinum testis).

-           fibrous septa radiate out from latter to form ~300 lobules containing seminiferous tubules which open into rete testis ® 15-20 vasa efferentia ® epididymis ® ductus from lower pole.

-           Within tubules  Sertoli cells provide structural & nutritional support (secrete androgen binding protein or ADB); Leydig cells found between tubules ® testosterone. 

Median scrotal septum separates the two halves of the scrotum (from dartos fascia)

Appendix testis = sessile cyst within tunica vaginalis at upper pole; = persistent mesonephric tubule. 

Blood Supply

Mainly testicular artery, collateral supply from cremasteric artery & artery to vas.

-           Testicular branches left and right, then penetrate tunica albuginea over surface of testis;

-           Ischaemia of testis unusual after division of testicular artery in abdomen; even cord division ® gradual atrophy rather than immediate ischaemia/infarction. 

Venous Drainage

Veins coalesce at mediastinum testis ® pampiniform plexus ® four veins on cord ® two at deep ring ® single on psoas major.  L ® L renal vein, R ® IVC

-           plexus mainly anterior to vas.  L veins may become varicose = varicocoele (?due to overlying pressure of sigmoid colon).  Ligation of testicular vein at internal ring cures this problem. 

Lymphatic Drainage

Testis ® par-aortic nodes (at L2, ie level of testicular artery origin).

Scrotal coverings ® superficial inguinal nodes \ don’t traverse scrotal skin to biopsy the testis. 

Innervation

Sympathetic outflow from T10 ® splanchnic nerves ® coeliac plexus ® fibres run with testicular arteries.  Sensory fibres follow same path.  No parasympathetic supply.  

Testicular Descent

Testis develops in posterior abdominal wall peritoneum, primordial germ cells from yolk sac migrate to the gonadal ridge.  Initially attached to mesonephros by the urogenital mesentery.

-           mesonephros ® ductus deferens, epididymis, ejaculatory duct & appendix epididymis.

-           paramesonephric duct (uterus & tubes in female) ® appendix testis and prostatic utricle.

At lower pole mesodermal gubernaculum is attached.

Testis descends during foetal growth: 7/12 ® deep ring, birth ® scrotum.

-           as they descend, they take the processus vaginalis with them, the peritoneal sac behind should get obliterated (if whole remains ® hernial sac; if distal part remains ® congenital hydrocoele)

Gubernaculum then degenerates. 

Cryptorchid testis = failure to descend ® defective spermatogenesis, androgens ok, malig potential.

-           remember cremaster muscle active in children – do not confuse retraction.

Epididymis & Ductus Deferens (361-2)

Epididymis attaches to posterior aspect of testis with vas medially.

-           a coiled tube (6m long uncoiled) with head (connected with vasa efferentia), body & tail (connected to ductus); see Pl362: tunica vaginalis covers lat epididymis & sinus

-           Ducts (thick wall of smooth muscle, columnar cells with steriocilia) traverses deep ring, pelvic side wall, pierces prostate and enters urethra via ejaculatory ducts. 

Blood: epididymis: branch of testicular artery; anastomoses with artery to vas. 

Nerve, veins and lymph as for testes.

Scrotum (361)

Subcutaneous tissue has no fat: instead dartos muscle (smooth; panniculus carnosis; contracts ® rugae)

-           dartos innervated by genital branch of GF nerve.

Superficial fascia continuous with Scarpa’s \ bleeding can track down from abdominal wall. 

Nerves:  Anterior axial line crosses scrotum.

Anterior 1/3 = ilioinguinal nerve (L1) and genital branch of GF nerve (L1)

Posterior 2/3 = scrotal branches of perineal nerve (S3) and perineal branch of posterior femoral cut nerve laterally (S2)

Blood: superficial and deep external pudendal arteries (from femoral); and scrotal branches of perineal (from pudendal).

Veins: External pudendal veins (® great saphenous).

Lymph: superficial inguinal nodes. 

Development: labioscrotal swellings and urogenital folds (meet at midline cutaneous raphe)

Torsion of Testis & Vestigial Elements

Patients susceptible to torsion have high termination of tunica vaginalis ®Bell-clapper” testes.

-           testis torts towards midline anteriorly; important for attempts at detorsion. 

Appendix testis, appendix of epididymis and inferior aberrant ductules can also all tort.