After circulatory system dissection is complete, review any parts of the digestive tract that you could not see clearly last week.

2) Hearts

Fish

Amphibian

Reptile

Bird

Mammal

Four chambered heart arose independently from three chambered reptilian heart

in birds and mammals.

- Birds retain right systemic arch; mammals retain left systemic arch

Probably no advantage to either design, but provides evidence of separate origin of 4 chambered heart

Reduction or loss of renal portal system can be seen as vertebrate trend.

Addition of post caval vein (or inferior vena cava) to replace posterior cardinals.

(Hepatic portal system is ubiquitous & does same job in all vertebrates.)

Shark: capillaries of tail - caudal vein - renal portal veins - afferent renal vein - kidney - efferent renal vein - posterior cardinal veins

Mud-puppy: Reduced posterior cardinal veins and replacement with one large vena cava to drain blood from kidneys.

Turtle: Posterior cardinal veins lost; more blood bypasses kidney

Pigeon: Endothermic, requires high blood pressure flow

Renal portal veins present, but can shut off with involuntary valves, shunting blood to vena cava

Cat: Renal portal vein to kidney lost.

Artery of dorsal aorta - renal artery - kidney - renal vein - vena cava

Kidney on separate circulation from rest of body: