Which mitotic microtubules radiate outward from centrosome into the region outside the body of the spindle? Their function is to position the spindle apparatus in the cell and determine the plane of cytokinesis. astral microtubules interpolar microtubules kinetochore microtubules polar microtubules Solution Astral microtubles. Actuly 2 hypothesis are their as how astral microtubls help in positioning of the spindle apparatus and determine the plane of cytokinesis. 1)astral stimulation hypothesis in which it is said that the astral microtubles carry a furrow inducing signal to the cell cortex and the signal from the two poles are focused into a ring at the spindle 2)astral relaxation hypothesis in which astral microtubles leads to the generation of negative signals as a result increase in cortical relaxation near to the poles..