Definition of "endocardium" [en•do•car•di•um]

• The thin serous membrane, composed of endothelial tissue, that lines the interior of the heart. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The endocardium is a thin, smooth membrane which lines and gives the glistening appearance to the inner surface of the heart; it assists in forming the valves by its reduplications, and is continuous with the lining membrane of the large bloodvessels."
• "The inner surface of the heart is lined by a serous membrane, the endocardium, which is smooth and firmly adherent to the muscular structure of the heart."
• "In the Flesh we see present in section: the myocardium, the endocardium, the vagus nerve and also the left ventricle of the heart for the large thickness of the myocardium."