The Spermatic Cord
The spermatic cord refers to a collection of vessels, nerves and ducts that run to and from the testes. They are surrounded by fascia, forming a cord-like structure.
This article will look at the anatomical course of the spermatic cord, its coverings, contents and clinical correlations.
The anatomical course of the spermatic cord is relatively short, beginning in the inferior abdomen and ending in the scrotum.
The spermatic cord is formed at the opening of the inguinal canal, known as the deep inguinal ring. This opening is located laterally to the inferior epigastric vessels.
The cord passes through the inguinal canal, entering the scrotum via the superficial inguinal ring. It continues into the scrotum, ending at the posterior border of the testes. Here, its contents disperse to supply the various structures of the testes and scrotum.
The contents of the spermatic cord are mainly bound together by three fascial layers. They are all derived from anterior abdominal wall:
- External spermatic fascia – derived from the aponeurosis of the external oblique.
- Cremaster muscle and fascia – derived from the internal oblique and its fascial coverings.
- Internal spermatic fascia – derived from the transversalis fascia.
The three fascial layers themselves are covered by a layer of superficial fascia, which lies directly below the scrotal skin.
The cremaster muscle forms the middle layer of the spermatic cord fascia. It is a discontinuous layer of striated muscle that is orientated longitudinally.
Clinical Relevance: Cremasteric Reflex
The cremasteric reflex can be stimulated by stroking the superior and medial part of the thigh. This produces an immediate contraction of the cremaster muscle, elevating the testis on the side that has been stimulated.
This spinal reflex consists of two parts:
- Afferent (sensory) limb – ilioiguinal or genitofemoral nerve
- Efferent (motor) limb – genital branch of the genitofemoral nerve.
The spermatic cord has a number of important structures that run to and from the testis:
- Testicular artery – a branch of the aorta that arises just inferiorly to the renal arteries.
- Cremasteric artery and vein – supplies the cremasteric fascia and muscle.
- Artery to the vas deferens – a branch of the inferior vesicle artery, which arises from the internal iliac.
- Pampiniform plexus of testicular veins – drains venous blood from the testes into the testicular vein.
- Genital branch of the genitofemoral nerve – supplies the cremaster muscle.
- Vas deferens – duct that transports sperm from the epididymis to the ejaculatory ducts, ready for ejaculation.
- Lymph vessels – these drain into the para-aortic nodes, located in the lumbar region.
- Processus vaginalis – a projection of peritoneum that forms the pathway of descent for the testes during embryonic development. In the adult, it is fused shut.
- Autonomic nerves
The pampiniform plexus is a network of veins, responsible for the venous drainage of the testes. It has a unique configuration, wrapping itself around the testicular artery
The testes function best at a temperature just below that of the body. The pampiniform plexus acts as a heat exchanger, cooling the arterial blood before it reaches the testes.
As it travels through the inguinal canal, the pampiniform plexus condenses into a single testicular vein. The right testicular vein drains into the inferior vena cava and the left testicular vein drains into the left renal vein.
The vas deferens is a straight, thick muscular tube that conveys sperm from the epididymis to the ejaculatory duct (formed by the convergence of the vas deferens and seminal vesicle duct). From the ejaculatory duct, sperm can pass through to the urethra.
The wall of the vas deferens contains a smooth muscle coat. This coat consists of three muscle layers – inner layer of longitudinal muscle, intermediate layer of circular muscle, and an outer layer of longitudinal muscle. There is a rich autonomic innervation of these muscle fibres, this permits fast movement of sperm towards the ejaculatory duct.
The anatomical course of the vas deferens is as follows:
- It is continuous with the tail of the epididymis.
- Travels through the inguinal canal.
- Moves down the lateral pelvic wall in close proximity to the ischial spine.
- Turns medially to pass between the bladder and the ureter.
- Joins the duct from the seminal vesicle to form the ejaculatory duct.
Clinical Relevance: Enlargement of the Scrotum
The scrotal sac is very distensible, and will enlarge in response to the size of its contents. There are a number of causes of scrotal swelling – here are the most common:
- Inguinal hernia – where the contents of the abdominal cavity protrude into the scrotum, via the inguinal canal.
- Hydrocoele – a collection of serous fluid within the tunica vaginalis. It is most commonly due to a failure of the processus vaginalis to close.
- Haematocoele – a collection of blood in the tunica vaginalis. It can be distinguished from a hydrocoele by transillumination (where a light is applied to the testicular swelling). Due to the dense nature of blood, light is unable to pass through.
- Varicocoele – gross dilation of the veins draining the testes.The left testicle is more commonly affected, as the left testicular vein drains into a smaller vessel, the left renal vein, at a perpendicular angle. A large varicocoele can look and feel like a bag of worms within the scrotum.
- Epididymitis – inflammation of the epididymis, usually caused by bacterial or viral infection.
Clinical Relevance: Testicular Torsion
Testicular torsion is fairly common medical emergency, where the spermatic cord twists upon itself. This can lead to occlusion of the testicular artery, resulting in necrosis of the testes.
Diagnosis can be confirmed via ultrasound and colour doppler scanning. The main clinical feature of testicular torsion is severe, sudden pain in one or both of the testes, where the onset is often during exercise or physical activity.