Look at its anterior surface from inside the mantle cavity and find the large, slit-shaped nephridiopore . An ultrafiltrate of the blood is produced in the pericardium. A nephrostome in the wall of the pericardium opens into the renopericardial canal which leads into the kidney. Blood in the surrounding hemocoel bathes the outside of the kidney and canal and modifies the ultrafiltrate inside by selective absorption and secretion. Finished urine is released into the back of the mantle cavity by the nephridiopore.
Circulatory System Find the pericardium again.
It is a small area located immediately posterior to the posterior end of the gill and on the left edge of the kidney. Notice that the efferent branchial vessel from the gill runs into its anterior corner. The heart is the brown organ within the pericardium. It is composed of an atrium and a ventricle. The ventricle is posterior to and is large.