THE CEPHALIC AORTA OF SEPIA-OFFICINALIS (CEPHALOPODA, DIBRANCHIATA) -STRUCTURAL MUSCULAR SPECIALIZATIONS OF A HIGH-PRESSURE VESSEL

Electron microscopic studies on the cephalic aorta of Sepia officinali s characterise the tunica media as a highly specialised type of cross- striated muscle with complex cord-like and branched-off z-patches. The se contain 10-nm filaments and show a lattice-like substructure which is evidence that they play a role in the particular viscoelastic funct ion of this vessel. Analyses of freeze-etched preparations as well as TEM sections demonstrate desmosome-like contacts and largely extended gap junction areas between the closely interdigitated muscle cells. Th ey suggest that the tunica media represents a functional syncytium in which the marginal muscle cells, the only ones to be innervated, can b e seen as pace-maker cells in modulating the tonus of the vessel.