Changes

In addition to cardiac muscle tissue, the heart wall also contains dense connective tissue that forms the fibrous skeleton of the heart. The fibrous skeleton is composed of dense connective tissue rings that surround the four heart orifices. The skeleton contains fibrocartilage in which nodules of bones (ossa cordis) may develop in some species. Although these bones occur most commonly in cattle, they are not restricted to this species. The skeleton performs several functions:

In addition to cardiac muscle tissue, the heart wall also contains dense connective tissue that forms the fibrous skeleton of the heart. The fibrous skeleton is composed of dense connective tissue rings that surround the four heart orifices. The skeleton contains fibrocartilage in which nodules of bones (ossa cordis) may develop in some species. Although these bones occur most commonly in cattle, they are not restricted to this species. The skeleton performs several functions:

It serves as a point of attachment for the heart valves

* It serves as a point of attachment for the heart valves

The cardiac muscle bundles insert onto the fibrous skeleton.

* The cardiac muscle bundles insert onto the fibrous skeleton.

It prevents the valves from overstretching as blood passes through them.

* It prevents the valves from overstretching as blood passes through them.

It acts as an electrical insulator thereby preventing the direct spread of action potentials from the atria to the ventricles.

* It acts as an electrical insulator thereby preventing the direct spread of action potentials from the atria to the ventricles.

===Chambers of the Heart===

===Chambers of the Heart===