Are frog hearts like human hearts?
The frog heart differs from the mammalian heart anatomically in that they are three chambered rather than four chambered. The pacemaker in the amphibian heart is the sinus venosus, a thin-walled sac that receives blood from the anterior and posterior caval veins and empties blood into the right atrium. The single ventricle receives blood from both atria and pumps blood out through the large artery called the truncus arteriosus (Figure 1). In contrast, the mammalian ventricle has separate left and right chambers, which prevent mixing of the venous and arterial blood.
