Page 18 - Long Axis contraction
This diagram shows the contraction vectors for the two oblique sets of cells in black, and their projection of these onto the short (green) and long (blue) axes. Any oblique cell will contribute to either, and those at 45 degree helical angle will contribute equally to both.
With the mid-wall devoted to short axis contraction and with significant assistance from the oblique cells, it is no surprise that short axis contraction appears so dominant. However, there is quite a lot of force directed along the long axis from the oblique sets, augmented by the few subendocardial longitudinal cells. It is clearly enough to shorten the cavity in the long axis. As the apex is near enough static, the excursion in the long axis is manifest as to and fro motion of the atrioventricular ring, as we saw in page 7. Moreover, the oblique layers are at opposing angles, keeping the net force nicely in line with the long axis.