principal 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.

prin·ci·pal piece

the principal part of the spermatozoon, which is about 45 mc;m long and has a characteristic fibrous sheath surrounding the axoneme.
References in periodicals archive ?
Further research revealed that the protein was being lost because it was not being confined to the principal piece of the tail.
The 1-1[micro]m long principal piece follows the middle piece.
And any sport in which the principal piece of equipment is called a sulky is hardly off to a flyer.
16 of 1975, amended by Acts 54 of 1986, Act 12 of 1990, and Act 8 of 2001 is the principal piece of legislation relating to the management of national parks in Dominica.

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