16 



THE TESTIS AND ITS RELATION TO REPRODUCTION 



tubuli recti pass into the mediastinum and join the anastomosing rete tubules 

 of the rete testis. 



The convoluted portions of the seminiferous tubules produce the sperm 

 (spermia; spermatozoa). In the human testis, the length of one of these 

 tubules is about 30 to 70 cm. and approximately 150 /i, to 250 fJ^ in diameter. 

 Each tubule is circumscribed by a basement membrane of connective tissue 

 and contains two cell types: 



( 1 ) supporting or Sertoli cells, and 



(2) spermatogenic cells or spermatogonia (see fig. 8 and Chap. 3). 



The cells of Sertoli are relatively long, slender elements placed perpen- 

 dicularly to the basement membrane to which they firmly adhere. These 

 cells may undergo considerable change in shape, and some observers believe 

 that they may form a syncytium, known as the "Sertolian syncytium." Others 

 believe them to be distinct elements. It is said that Sertoli cells may round 

 up and form phagocytes which become free from the basement membrane 

 and move, ameba-like, in the lumen of the seminiferous tubule, phagocytizing 

 degenerating sperm cells. However, their main function appears to be asso- 

 ciated with the development of sperm during the period when the latter 

 undergo their transformation from the spermatid condition into the adult 



SERTOLI CELL 



SEMINIFEROUS TUBULE 



CELLS OF L E YD IG 



BASEMENT MEMBRANE 



CAPILLARY 



NTERSTITIAL TISSUE 



SPERMATOGONIUM 



Fig. 8. Semidiagrammatic representation of section of cat testis, showing seminiferous 

 tubules and interstitial tissue, particularly the cells of Leydig. 



