Circulatory System
Step 1
Lift the liver gently. Identify the heart, covered by a membranous covering (the pericardium). With forceps, lift the covering, and gently slit it open. The heart consists of a single, thick-walled ventricle and two (right and left) anterior, thin-walled atria.
Step 2
Locate the three large veins that join together beneath the heart to form the sinus venosus. (To lift the heart, you may have to snip the slender strand of tissue that connects the atria to the pericardium.) Blood from the sinus venosus enters the right atrium. The left atrium receives blood from the lungs.
Step 3
Find the conus anteriosus, a single, wide arterial vessel leaving the ventricle and passing ventrally over the right atrium. Follow the conus anteriosus forward to where it divides into three branches on each side. The middle artery on each side is the systemic artery, which fuses behind the heart to become the dorsal aorta. The dorsal aorta transports blood through the body cavity and gives off many branches. The posterior vena cava begins between the two kidneys and returns blood to the sinus venosus.