Term Name:	sperm annulus
Synonyms:
Definition:	The ring-like, filamentous structure located at the distal end of the midpiece of the sperm flagellum; the annulus is thought to form a diffusion barrier between the midpiece and the principal piece and serve as a stabilizing structure for tail rigidity.
Ontology:	GO: Cellular Component [GO:0097227]    QuickGO    AmiGO