Final answer:
The endocardium is the innermost layer of the heart wall, made up of endothelium and connective tissue, and it lines the heart's chambers and valves. Option 2 is correct.
Step-by-step explanation:
The innermost layer of the heart wall is known as the endocardium. It is composed of a type of simple squamous epithelium called endothelium and is responsible for lining the heart chambers and heart valves. This layer is reinforced with a thin layer of connective tissue that connects it to the myocardium, which is the muscular middle layer of the heart wall.
Each layer of the heart has distinct functions: the epicardium is the outermost layer of the heart wall, the myocardium makes up the bulk of the heart wall, and the endocardium, where it provides a smooth lining and plays a role in protecting the inner parts of the heart.
The innermost layer of the heart is the endocardium. It is made up primarily of simple epithelial cells and covers the heart chambers and valves. A thin layer of connective tissue joins the endocardium to the myocardium.