Through the occluding junctional complexes of the Sertoli's cells a "blood/testicle" barrier is created in the tubule. This means that outside this barrier, in the tubular periphery, cells, substances and hormones from the blood have unhindered access.
On the other hand, the inner compartment of the tubule is protected by the barrier, which is selectively permeable and serves as an entry check. This is of practical importance because haploid cells in the inner part of the tubule exhibit surface antigenic properties, different from all other body cells. They must thus be kept secluded from the immune system of the organism by the "blood/testicle" barrier.