middle piece

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a part or portion.
end piece the terminal portion of the tail of the spermatozoon. See illustration at spermatozoon.
middle piece an anterior portion of the tail of the spermatozoon, between the neck and the anulus. See illustration at spermatozoon.
principal piece the main portion of the tail of a spermatozoon, beginning at the anulus and gradually tapering toward the end piece. See illustration at spermatozoon.

mid·dle piece

a part of the spermatozoon characterized by an axoneme and by a sheath of mitochondria arranged in a tight helix.
References in periodicals archive ?
Sperms with abnormally forked nuclei and degenerating mitochondria in the middle piece were also noticed in these specimens (fig.
The tail is composed of a middle piece, principal piece, and end piece.
Anurekha herself choreographed the middle piece, with the music and rhythmic accompaniment conceived by Ronu Majumdar, India's top flute player, and Partha Sarathi Mukherjee, the group's brilliant tabla player, who found himself with a walk-on role.
She's got more power behind the saddle and in the middle piece.