The seminiferous tubules are where the production, maturation and transport of the sperm cells takes place. The seminiferous tubules are located in the male testicles, which are the two oval-shaped organs on located beneath the penis.
In each testicle, there are approximately 800 seminiferous tubules. This is where meiosis and the later development of sperm cells takes place.
The seminiferous tubules loop tightly throughout the testes to an incredible length, as much as a mile long in total between both testicles. In adult men, these tubules produce thousands of sperm each and every second through a process known as spermatogenesis. This sperm production in the tubules takes place inside over 200 compartments that are separated by fibrous septae of the tunica albuginea.
Stem cells located on the outside of the tubules divide through mitosis and then move inward. They then continue developing on the inside walls of the seminiferous tubules, where they become germinal sperm cells (spermatogonia).
These germinal sperm cells slowly move through the seminiferous tubes for the next 60 or more days, continuing on to the central tubule and to the upper back of the testes to the web-like rete testis. They then make their way through the efferent ductules for storage in the epididymis on the outer areas of the testes.
The tissue of the seminiferous tubules are lined with sertoli cells, which are a specialized cell type that are responsible for creating new sperm. The Sertoli cells are essential for the nourishment and the development of the sperm cells. They do so by secreting a protein called testis-determining factor that increases the concentration of testosterone inside the seminiferous tubules.
Until they develop into spermatozoa, the maturing sperm cells receive nutrients and raw materials from the sertoli cells. However, at this point the sperm are not fully complete in their development when transported out of the seminiferous tubules. They must still finish maturing in the epididymis, as they must still develop their tails which give them their ability to swim (motility).
There are two distinct types of seminiferous tubules:
- Convoluted seminiferous tubules – The twisting, curved tubules on the side of the testes where sperm cells are produced.
- Straight seminiferous tubules – The short, straight canals that continue from the convoluted tubules to transport sperm cells to the rete testes, a network of small tubes in the testicle that helps move the sperm cells from the testicle to the epididymis