(A) Longitudinal slightly oblique section through an acrosomeal process which is everting, causing the inner surface of the acrosomal vesicle to become the outer surface of the acrosomal process. Bar: 0.5um (This is also applicable to B, C, D, E).
(B),(C) Longitudinal slightly oblique serial sections. An electron-dense structure is exposed outside and the acrosomal process is extending. Stacked structures consisting of many rings with a constant diameter of about 35nm in diameter, are observed scattered around sperm. These structures are produced during oogenesis.
(D) Longitudinal section through the reacting sperm. The remnants of the electron-dense structure (EDS) is observed (thick arrow). The acrosomal outer membrane has the lining inside (arrow).
(E) Longitudinal section through a sperm after the acrosomal reaction. The acrosomal process(about 2um in length)has extended.
(F) Enlargement of the anteriormost region of the acrosomal process in (E). Fuzzy materials decorate the external surface of the process. Fibrous structures(presumable actin filaments)are observed in the process. Bar:0.1um.
