After They Have Elongated, the Cells of the Neural Epithelium

Multiple Choice

After they have elongated, the cells of the neural epithelium become constricted at one end, causing them to become wedge shaped and leading the entire layer of cells to curve inward. What causes this constriction?

A) contraction of microtubules in the cytoplasm just above the basal cell membrane
B) lengthening of microtubules in the cytoplasm just below the apical cell membrane
C) contraction of a band of actin filaments that assemble in the cortical region of the cells just above the basal cell membrane
D) contraction of a band of actin filaments that assemble in the cortical region of the cells just beneath the apical cell membrane
E) shortening of microtubules in the cytoplasm just below the apical cell membrane