Diagram of a concept of the organisation of germ cells in the seminiferous epithelium of the human testis. The sequence of germ cell maturation is shown as a spiral gyrating inwards to the lumen of the seminiferous tubule. This pattern is found in the human and several no-human primates but uncommon in most other animals. Ad,Ap,B = type A dark/pale,and B spermatogonia; PL,L,Z,P,II = preleptotene,leptotene,zygotene,pachytene,meiosis II spermatocytes; S = various types of spermatids; Rb = spermatid residual body. |