Each seminiferous tubule is lined on its inside by which of the following?

A. Male germ cells

B. Interstitial cells 

C. Sertoli cells

Each seminiferous tubule is lined on its inside by two types of cells called male germ cells and Sertoli cells. The male germ cells undergo meiotic divisions, which lead to sperm formation, while the Sertoli cells provide nutrition to the germ cells and the sperm cells formed. 

The regions outside the seminiferous tubules are called interstitial spaces. These contain small blood vessels and interstitial cells or Leydig cells. Leydig cells synthesize and secrete testicular hormones called androgens (testosterone). The testosterone from Leydig cells enters the seminiferous tubules by diffusion, and promotes spermatogenesis (sperm formation).