Cardiovascular

The mouse and human cardiovascular systems have many features in common; however, there are also important differences. As is true in all mammals, both species have four-chambered hearts: left and right atria, a dominant left ventricle, and a thinner-walled right ventricle. Although the mouse heart is far smaller than the human heart, the ratio of heart to body weight is similar in both species, as is the relative thicknesses of the right and left ventricular walls. Because of the small dimensions of the mouse heart, much of the examination that is done macroscopically on the human heart is better done microscopically on the mouse heart. In both species, the majority of heart mass is composed of cardiomyocytes, but significant numbers of other cell types are present, including endothelial cells, fibroblasts, and leukocytes. Important differences between the mouse and human heart include the general shape of the heart; location of the coronary arteries; structure of the valves; thickness of the pericardium, epicardium, and endocardium; and prominence of the cardiac skeleton. Although the anatomy and histological structure of the vasculature in the two species share many features, they have important differences, including the thinner walls of mouse arteries and the prominent presence of cardiomyocytes around mouse pulmonary veins.