Page 793 - Atlas of Histology with Functional Correlations

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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