the degree of muscular specialization varies over a spectrum , however , ranging from a delicate endowment of thin myofilaments in the capillary myoendothelial cells to highly specialized myoendothelial cells in the main pulsating dorsal blood trunk , which serves as the worm 's `` '' heart '' '' or propulsive `` '' aorta . '' ''
C0025979
myofilaments
C0007634
cells