Real testes 28 days (IMAGE) Bar-Ilan University Caption Image of real testes of 28-day-old mice. The Sertoli cells, which are the cells responsible for the formation of the tubules in the testicle, are marked in red and the unmarked tubules of the testicle in which the sperm cells are produced are clearly seen Credit Aviya Stopel Usage Restrictions None License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.