Epididymis is an important part of the male reproductive system. It is a firm structure lying posterior to the testis with vas deferens lying on its medial side. It is in the form of a narrow, coiled tube connecting the efferent ducts from the rear of each testis to its vas deferens.
Structure of epididymis:
Epididymis consists of an expanded upper end called the head, a body and an inferior pointed tail. Laterally, between the testis and the body, there is a distinct groove lined with the inner visceral layer of tunica vaginalis and is called the sinus of the epididymis.
Epididymis is a much coiled tube. When fully stretched, it is nearly 20 ft. long. The vas deferens emerges from the tail of epididymis as a tube and enters the spermatic cord.
Functions of epididymis:
The long length of the epididymis provides storage space for spermatozoa and allows them to mature before release. One of the primary functions of epididymis is to absorb fluid and add additional substances to the seminal fluid to nourish the maturing sperm.
Blood supply of epididymis:
Epididymis shares a common blood supply with testis. The major part of its blood supply comes from paired testicular arteries, which are branches of abdominal aorta. These arteries form part of the spermatic cord, which passes through the inguinal canal and reaches the testis.
The venous drainage occurs through the Pampiniform plexus, which eventually becomes reduced to a single vein known as testicular vein. The testicular vein eventually drains into the inferior vena cava on right side and left renal vein on left side.
Lymph drainage of epididymis:
The testicular lymph vessels ascend in the spermatic cord and end in the para-aortic lymph nodes at the level of first lumbar vertebra. This is to be expected because during development, testis has migrated from high up on the posterior abdominal wall, down through the inguinal canal and into the scrotum. It drags its blood supply and lymph vessels after it.