Answer:
Valves of the heart do the endocardium extenstions.
Step-by-step explanation:
Endocardium is the inner most layer of heart containing tissue that lines the heart chamber and the outer most layer of the heart is called epicardium.
The main function of this structure is to protect the valves and heart chamber.
The endocardium consists of endothelial cells that controls myocardial function.
The homeometric and heterometric regulation is separated by myocardial system.
The endocardium also functions as a blood heart barrier thus controlling the ionic composition withih which the cadiomyocytes bathe.