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aster

 [as´ter]
a structure occurring in dividing cells, composed of microtubules radiating from a centrosome. The two asters are the poles of the spindle apparatus.
 Asters separating in prophase of mitosis. From Dorland's, 2000.

as·tro·sphere

(as'trō-sfēr),
A set of radiating microtubules extending outward from the cytocentrum and centrosphere of a dividing cell.
[G. astron, star, + sphaira, ball]

aster

(ăs′tər)
n.
Biology A star-shaped structure formed in the cytoplasm of an animal cell during mitosis, having raylike microtubules that surround the centrosome.

as·tro·sphere

(as'trō-sfēr)
A set of radiating microtubules extending outward from the cytocentrum and centrosphere of a dividing cell.
Synonym(s): aster, attraction sphere.
[G. astron, star, + sphaira, ball]
Asterclick for a larger image
Fig. 54 Aster . Generalized form.

aster

a group of blind-ending SPINDLE MICROTUBULES radiating out from the CENTRIOLES of dividing cells in lower plants and all animals. The aster function is uncertain, but does not seem to be concerned with spindle formation.