Epididymis and Vas Deferens

Epididymis

The epididymis is the structure that wraps around the outside of the testis—kind of like a half wig. If I were to cut this picture on the right with a transverse cut, I’d see this histological picture.  This is the testis with its coiled seminiferous tubules. This crescent shape here is the epididymis with its coiled tube. Look at how the diameter of the epididymis is larger.   There are some remnants of the spermatic cord over here. I’m not 100% sure where the ductus deferens is.

Spermatids enter the epididymis from the efferent ductules coming off the rete testis.  It can take 20 days to travel through the epididymis.  Sometimes spermatozoa will wait there 40 to 60 days for an ejaculatory event. You can think of the epididymis as a waiting area where sperm are stored until ejaculation occurs.  When ejaculation happens, sperm travel through the ductus deferens. They then enter the urethraThe tube that carries urine from the bladder to the outside of the body.. In the urethra, they are mixed with fluid from other glands. This mixture prepares them for release.  If they are not ejaculated, the epididymis will break down the old sperm, recycling their components to the seminiferous tubules.

Epididymis Functions

Immature spermatozoa  — still in the form of spermatids — are moved into the epididymis by small waves of peristalsis Rhythmic contractions of smooth muscle that move food through the digestive tract.. Inside the epididymis, they undergo spermiogenesis. During this process, they mature into their final form by shedding their cytoplasmThe gel-like substance within a cell that contains organelles and cytosol.. They also fully form their flagellaLong, whip-like structures used by some cells (e.g., sperm) for movement..  The epididymis is lined with pseudostratified columnar or simple columnar cellsThe basic structural and functional units of life. with ciliaHair-like projections on the surface of some cells that move fluids or particles. on them.  These cilia move sperm along the epididymis despite their level of flagella formation.

The fluids in the lumenThe inside space of a hollow organ or structure. of the epididymis are different than those in the lumen in the seminiferous tubules.  The epithelial cells of the epididymis adjust this fluid to better facilitate spermiogenesis.

Vas Deferens (ductus deferens)

The ductus deferens carries spermatozoa upward and over the bladderA muscular organ that stores urine before excretion., eventually joining the urethra. Along this journey, spermatozoa will mix with fluids from three accessory glands to form semen. These fluids contain sugars and enzymesProteins that speed up chemical reactions in the body..  The vas deferens is lined with pseudostratified columnar ciliated epithelial tissue. It retains the cilia in case those flagella aren’t working well.  There is a very thick layer of smooth muscle surrounding the vas deferens.  This smooth muscle is activated in ejaculation to forcefully propel the spermatozoa.

The ductus deferens is the structure that’s cut during a vasectomy. After a vasectomy, sperm continues to be produced but is reabsorbed by the body. Physicians confirm the success of the procedure by monitoring sperm levels to ensure they drop to zero.