innermost layer of tissue that lines the heart
The Endocardium is the innermost layer of tissue which lines the inside of the heart. It plays a role in controlling the function of the myocardium, the heart muscle. The endocardium is made of simple epithelial cells similar to those which line blood vessels.
In addition to lining the inside of the heart, the endocardium also regulates heart contractions and aids cardiac embryo development.