Page 793 - Atlas of Histology with Functional Correlations
P. 793

bound  acrosomal  vesicle  next  to  the  nuclear  envelope.  The  location  of  the

               acrosomal vesicle indicates the anterior region of the developing sperm. During
               the  acrosomal  phase,  both  the  acrosomal  vesicle  and  the  acrosomal  granule
               spread over the anterior two thirds of the condensing spermatid nucleus as an
               acrosome  cap.  Also  during  this  phase,  centrioles  migrate  to  the  opposite  or
               posterior pole of the spermatid and assemble the microtubules to form the sperm

               tail,  or  flagellum.  The  fully  formed  acrosome  contains  several  hydrolytic
               enzymes, such as hyaluronidase, acid phosphatase, and protease with trypsin-like
               activity. The release of acrosomal enzymes assists the sperm in penetrating the

               cells  (corona  radiata)  and  the  membrane  (zona  pellucida)  that  surrounds  the
               ovulated  oocyte  and  allows  fertilization.  During  the  maturation  phases,  the
               elongated spermatid heads are embedded in the cytoplasm of supportive Sertoli
               cells.  Also,  the  plasma  membrane  of  the  spermatid  moves  posterior  from  the
               nucleus to cover the developing flagellum (sperm tail), which now extends into

               the lumen of the seminiferous tubule. The mitochondria also migrate to and form
               a  tight  sheath  around  the  middle  piece  of  the  developed  flagellum.  The  final
               maturation  phase  is  characterized  by  the  shedding  of  the  excess  or  residual

               cytoplasm  of  the  spermatid  and  release  of  the  sperm  into  the  lumen  of  the
               seminiferous tubule. The supportive Sertoli cells then phagocytose the residual
               cytoplasm.













































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