Superficial Bulbospiral and Sinospiral Muscle Layer
Superficial Bulbospiral Muscle Layer
The superficial bulbospiral muscle
originates from the left half of the fibrous skeleton and gives
rise to the muscle fibers which circle anteriorly around the
obtuse margin of the heart and posteriorly around the
diaphragmatic surface to end as muscle columns at the base of the
posterior papillary muscle groups of the atrioventricular valves.
Superficial Sinospiral Muscle Layer
The superficial sinospiral muscle
originates at the orifice of the tricuspid valve and spirals
around the anterior surface of the right ventricle. Both
superficial groups converge on the apex of the heart making a
vortex of muscular columns in the ventricular wall both
anteriorly and posteriorly and project into the ventricular
cavities as the papillary muscles.