Nervous system

Reno-pericardial system

Excretory system : The kidney forms a compact organ with a small lumen that lies in the rear mantle cavity roof and encloses the region where the ctenidium and endostyle curve into the food groove ( Fig. 8A). The kidney typically has a curved tetrahedral outline in dorsal view, but may be deformed somewhat by contraction at fixation. It is bordered at its dorsolateral edges by two prominent blood vessels that converge at its pointed anterior tip; the vessel to the right emerges from the rectal sinus (see rectum under Alimentary system) and that at the left is confluent with the afferent branchial vessel ( Figs 5D, 8A). At its ventroposterior side, the kidney is bordered by the efferent vein of the nephridial gland. The efferent branchial vein lies in close proximity to the afferent branchial vein at the posterior end of the kidney, and both are incompletely separated by a constriction. A relatively large nephropore opens to the ventral surface of the kidney at the right side, roughly at the posterior third. It connects the kidney lumen to an expansion of the ureter lying between the kidney and the rectum, and lies just in front of the vertical membrane separating the pallial cavity from the pericardium. A small reno-pericardial duct at the right posterior side of the kidney lies in close proximity to the nephropore. The ureter continues anteriorly as a tall and narrow uninterrupted chamber between the pallial gonoduct and the rectum. As described above, the ureter opens anteriorly via the urinary pore.

Heart and circulation: The pericardium ( Fig. 8A) forms a voluminous, elongate chamber bounding the rear of the mantle cavity in the central to left aspect, and is strongly compartmentalized at its right ventral side by the anterior digestive gland. Dorsally to the right, the pericardium is bordered by the rectum, but at the far right the pericardium forms the body wall, and anteriorly at the far right it is separated by a membrane from the ureter that continues anteriorly. Dorsally along the mid-line and at the left it is bordered by the intestine and the style sac, whereas the left anterior side is bordered by the kidney, the posterior gill and food groove ( Fig. 8A). The heart lies antero-ventrally at the far left within the pericardium. The large auricle is somewhat anterior and to the left of the smaller, more muscular ventricle, and receives blood (=haemolymph) from a blood sinus at the base of the kidney (=the efferent vein of the nephridial gland), which is confluent with the afferent and efferent branchial veins, and via the efferent branchial vein it is connected to the auricle. The efferent vein of the nephridial gland is at the right continuous with a blood sinus at the base of the membrane separating the ureter from the pericardium, which is connected directly to the rectal sinus. From the left, posterior aspect of the ventricle a short constriction separates the ventricle from the bulbous aorta. The bulbous aorta produces two posterior visceral branches and the anterior cephalic aorta which passes to the left of the oesophagus into the cephalic haemocoel. The left branch of the visceral aorta penetrates the viscera shortly behind the ventricle below the style sac, whereas the right branch continues posteriorly along the floor of the pericardium at the anterior end of the digestive gland and further alongside the posterior oesophagus.