Corpus: Epididymis

The epididymis is a male reproductive organ that functions as a reservoir for sperm. It is the site where sperm cells undergo maturation, becoming fully functional sperm.

2.1. Topography and organisation

The epididymis is located along the posterior edge and upper pole of the testicle. It contains the epididymal duct, a highly coiled tube approximately 6 meters long when fully extended. Externally, the epididymis is covered by a thin capsule, which is a continuation of the tunica albuginea, and is enveloped, except where it attaches to the testicle, by the epiorchium, the inner layer of the tunica vaginalis of the testicle. The connective tissue that links the epididymis to the testicle is known as the mesepididymis.

The epididymis measures about 5 to 6 cm in length in adults and is divided into three sections, though without distinct boundaries:

• Head: Caput epididymidis
• Body: Corpus epididymidis
• Tail: Cauda epididymidis

The efferent ducts are located in the head, serving as a bridge between the testicles and epididymis, through which immature sperm cells are transported.

2.2. Supply

The connective tissue of the epididymis is highly vascularized and innervated. Arterial supply comes from the testicular artery, which originates from the abdominal aorta, while venous drainage occurs via the pampiniform plexus.

The epididymis receives autonomic innervation from nerve fibers originating in the coeliac ganglia and the inferior hypogastric plexus. Sympathetic fibers regulate both blood flow to the epididymis and contraction of its smooth muscles. Lymphatic drainage occurs via the lumbar lymph nodes and internal iliac lymph nodes.

2.3. Embryology

The epididymal duct develops alongside the deferent duct, seminal vesicle, and ejaculatory duct from the Wolffian duct.

As a remnant of the Wolffian duct, a small, often pedunculated structure called the epididymal appendix can sometimes be found at the head of the epididymis.

The epididymis plays a crucial role in the maturation and storage of sperm. As sperm cells pass through the epididymal duct, they undergo significant changes in both their morphology and functionality, a process essential for achieving motility and the ability to fertilize an egg. By the time sperm reach the end of the epididymal duct, they are fully mature and ready for ejaculation.

Inflammation of the epididymis, referred to as epididymitis, is a common condition. It typically results in a painful, often significant enlargement of the epididymis, which can be tender to touch.