The structure of the vas deferentia, also known as the ductus deferens, is an important component of the male reproductive system. It is a muscular tube that carries sperm from the epididymis to the ejaculatory duct. The free end of vas deferentia bears stereocilia.

Stereocilia are microvilli-like structures that are found in certain types of epithelial cells, including those lining the vas deferentia. They are long, non-motile projections that are specialized for absorption and secretion. In the vas deferentia, stereocilia help to propel sperm forward by absorbing fluid from the lumen and secreting it into the surrounding tissue. This creates pressure that moves the sperm along the duct.

Other structures that are found in the vas deferentia include:

- Ciliated cells: These are cells with hair-like projections called cilia. They are found in the lining of the epididymis and help to move sperm along by creating a rhythmic, wave-like motion.
- Pseudostratified columnar epithelium: This is the type of tissue that makes up the lining of the vas deferentia. It is so named because it appears to be layered, but in fact all of the cells are attached to the basement membrane.
- Leydig cells: These are specialized cells found in the testes that produce testosterone, the male sex hormone.

In summary, the free end of vas deferentia bears stereocilia, which are specialized structures that help to propel sperm forward by absorbing and secreting fluid.