What are the two types of cardiac muscle cells?

There are two major types of cardiac muscle cells: myocardial contractile cells and myocardial conducting cells. 

Myocardial Contractile Cells

Myocardial contractile cells are the most abundant cells in the cardiac muscle tissue. They comprise the bulk of the heart's muscle mass, making up almost 99% of the cells present in the atria and ventricles of the heart. 

The myocardial contractile cells are primarily responsible for the mechanical contraction of the heart. When stimulated by electrical impulses, they contract rhythmically and synchronously, generating the force needed to pump blood throughout the body.

Myocardial Conducting Cells

Myocardial conducting cells comprise only 1% of the cardiac muscle cells. They are responsible for initiating and conducting the electrical impulses (action potential) that control the heartbeat. 

The myocardial conducting cells serve as the heart's natural pacemakers, setting the rhythm and coordinating the contractions of myocardial contractile cells. They are also called pacemaker cells.   

Both, the myocardial contractile cells and myocardial conducting cells, work together to maintain the heart's function.