| piece | A part or portion. End piece, a part of the spermatozoon consisting of an axoneme surrounded only by the flagellar membrane. (05 Mar 2000) |
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| middle piece | A part of the spermatozoon characterised by an axoneme and by a sheath of mitochondria arranged in a tight helix. Principal piece, the principal part of the spermatozoon, which is about 45 um long and has a characteristic fibrous sheath surrounding the axoneme. (05 Mar 2000) |
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| end-piece | The terminal part of the tail of a spermatozoon consisting of the axoneme and the flagellar membrane. (05 Mar 2000) |
| Fab piece | The antigen-binding fragment of an immunoglobulin molecule, consisting of both a light chain and part of a heavy chain. Synonym: Fab piece. (05 Mar 2000) |
| Fc piece | <immunology> The constant region on an immunoglobulin molecule. The area that is exactly the same on all antibodies. The region is found on the heavy chains and is not involved in binding antigens. (09 Oct 1997) |