The Skeleton of the Heart consists of fibrous tissue and creates the central support of the heart. It is composed of fibrous rings that surround the atrioventricular, pulmonary, and aortic orifices. These rings provide circular form and rigidity to the atrioventricular orifices and roots of the aorta and pulmonary trunk. They also provide connection to the valves and prevent dilatation of these orifices. The cardiac valves are firmly connected to this skeleton. The cardiac skeleton together with membranous part of interventricular septum also gives attachments to the cardiac muscle fibres.
The fibrous rings around the atrioventricular orifices separate the muscle fibres of atria from those of the ventricles, but provide connection to such fibres. Thus there’s no muscular continuity between the atria and ventricles, with the exception of the atria ventricular bundle (bundle of His) of the conducting system.
A. The skeleton of the heart enables cardiac muscle to contract against the rigid base.
B. The fibrous rings support the bases of the cusps of the valves and prevent the valves from stretching and becoming incompetent. The aortic ring is the strongest.
Points to be noted:
A. The atrioventricular fibrous rings (AV rings) create the figure of ‘8’.
B. The large mass of fibrous tissue between AV rings and aortic ring is termed trigonumfibrosumdextrum. In a few mammals like sheep, elephant, etc. a bone- the oscordis develops in it.
C. The small mass of fibrous tissue between the fibrous rings around semilunar valves is termed as trigonumfibrosumsinistrum.
D. The tendon of infundibulum binds the posterior surface of the infundibulum to the aortic ring.