The cephalic aorta of Sepia officinalis (Cephalopoda, Dibranchiata): structural muscular specialisations of a high-pressure vessel

Abstract

Electron microscopic studies on the cephalic aorta of Sepia officinalis characterise the tunica media as a highly specialised type of cross-striated muscle with complex cord-like and branched-off z-patches. These contain 10-nm filaments and show a lattice-like substructure which is evidence that they play a role in the particular viscoelastic function 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. They suggest that the tunica media represents a functional syncytium in which the marginal muscle cells, the only ones to be innervated, can be seen as pace-maker cells in modulating the tonus of the vessel.