Question

Trace the path of a drop of blood through the body of a shark by making a sequential list of named vessels, heart chambers, and organs. Begin in the anterior intestinal vein on the outside of the small intestine and end with the internal carotid artery leading to the brain.

Answer 1

The circulatory system of shark or dogfish consist of one atria and one ventricle with well developed sinus venosus and conus arteriosus. The elaborate path of the trace of blood starting from anterior intesyinal vein is as follows:

Anterior intestinal veins draining outside from small intestine along with gastric vein draining from stomach, lienomesenteric vein from small intestine, pancreaticomesenteric veins from pancreas together form hepatic portal vein which enter the liver and subdivide. From the liver, blood is drained via hepatic veins of the systemic venous system to the sinus venosus. The renal portal system takes blood from caudal vein in the tail and enters kidneys and finally drains into the posterior cardinal veins and then to the posterior cardinal sinuses. The posterior cardinal sinus also receives the lateral abdominal vein that starts at pelvic fin where it receives iliac vein and passes along lateral body wall. It then receives brachial vein, then turns and become subclavian vein and enter common cardinal vein and then to sinus venosus. The venous blood after reaching atrium passes to the gills where oxygenation takes place and finally it returns back to the ventricle. The oxygenated blood then circulated via aorta to upper parts of body viz. head by internal carotid artery which is a part of anterior cardinals.