The Scrotum and its Contents: Testes, Epididymis and Spermatic Cord

The Scrotum

Fig 1.0 - Overview of the scrotum and its contents

Fig 1.0 – Overview of the scrotum and its contents

The scrotum is a cutaneous sac, forming an expansion of the perineum. It contains the testes, epididymis and the initial part of the spermatic cord. The scrotal sac is embryologically derived from the genital folds.

The scrotum has a different blood supply, lymphatic drainage, and nerve supply to its contents, due to their different embryological derivation. The scrotum receives arterial supply from the anterior and posterior scrotal arteries, and nervous supply from the scrotal nerves. Lymph drains to the nearby superficial inguinal lymph nodes.


Testes

The testes are the male gonad; the site of gamete production and testosterone. They are a paired structure, and have an elliptical shape.

Coverings of the Testes

Fig 1.0 - Sagittal section through a testicle, showing the two coverings.

Fig 1.1 – Sagittal section through a testicle, showing the two coverings.

Each testicle has two coverings. The first, the tunica vaginalis, is derived from peritoneum, surrounding the testes as they descend from the abdomen to the scrotum. They are also surrounded by a fibrous capsule, called the tunica albuginea. This structure consists of thick connective tissue, and penetrates into the testicle, splitting it into lobules.

There is an important distinction between the two layers; the tunica vaginalis merely surrounds the testes, closely covering the anterior surface and sides. The tunical albuginea encloses the testes.

Vascular Supply and Lymphatic Drainage of the Testes

The testes have a counter intuitive vascular supply. They receive blood from paired testicular arteries, which arise directly from the abdominal aorta. Venous drainage is achieved via paired testicular veins. The left testicular vein drains into the left renal vein , while the right testicular vein drains directly into the inferior vena cava.

Lymph from the testes drains to the paraaortic nodes. This is different to the scrotum itself, which drains to the nearby superficial inguinal nodes.

This slightly confusing vascular and lymphatic supply can be explained by the development of the testes. During embryonic development, the testes form in the abdomen, on the posterior wall. They then descend into the scrotum, taking their vessels and lymphatics with them.

Fig 1.3 - Venogram of the varicocoele.

Fig 1.3 – Venogram of the varicocoele.

Clinical Relevance: Testicular Lumps and Swellings

There are many different causes to testicular lumps and swellings:

  • Hydrocoele – Accumulation of fluid between the testicle and the tunica vaginalis, usually caused by persistence of the processus vaginalis.
  • Haematocoele –  Accumulation of blood between the testicle and the tunica vaginalis.
  • Varicocoele – Dilation of the pampiniform plexus (venous drainage) of the testicle.
  • Epididymal cyst – Collection of fluid on the head of the epididymis.
  • Testicular tumour – Uncommon, usually a tumour of the germ cells.

The Epididymis

The epididymis is a structure that lies on the posterolateral surface of the testes. Its main function is to store the sperm formed in the testes. It consists of a single tube, which has a very convuluted path.

It can be split into three parts;

  • Head – formed by the convergence of the efferent ductules from the rete testis
  • Body – comprised of a single tube, which is extremely coiled
  • Tail – the area of transition between the epididymis and vas deferens

The vas deferens then enters the spermatic cord, and empties into the urethra during ejactulation.

Fig 1.1 - The different sections of the epididymis

Fig 1.3 – The different sections of the epididymis


Spermatic Cord

The spermatic cord carries vessels and nerves to and from the testes, and suspends the testis in the scrotal sac.

It contains:

  • Vas deferens
  • Testicular artery, cremasteric artery, artery to vas deferens
  • Testicular veins (in a unique arrangement called the pampiniform plexus)
  • Genital branch of the genitofemoral nerve
  • Lymphatics

The  above structures exit the abdomen through the deep inguinal ring. In doing so, they ‘pull’ the fascial coverings of the abdomen with them, covering the spermatic cord. This then travels through the inguinal canal, and exits into the scrotum.

The coverings of the spermatic cord (superficial to deep):

  1. External spermatic fascia: derived from the aponeurosis of the external oblique
  2. Cremasteric fascia: derived from aponeurosis of the internal oblique
  3. Internal spermatic fascia: derived from the transversalis fascia

The testes work best at a temperature slightly below body temperature. The pampiniform plexus helps lower the testicular temperature. The plexus consists of a network of small veins, which surround the testicular artery, and act as a heat exchanger, cooling the blood going to the testes.

Clinical Relevance: Testicular Torsion

Testicular torsion is fairly common medical emergency, where the spermatic cord twists upon itself. This results in occlusion of the testicular arteries, causing ischaemia of the affected testicle.

A common presentation of testicular torsion is lower abdominal pain after physical activity. Investigations are usually an ultrasound and colour doppler, looking for evidence of occluded arterial blood flow.

The spermatic cord can be untwisted manually, or surgically.

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