because venous blood from te mesentery, spleen and pancreas are filtered by the liver before it returns to the heart.
In either case there is a bed of veins called the pampiniform plexus which directly drain the organs blood supply. The plexus then drains into discreet veins; from the ovaries, the ovarian veins and from the testes, the testicular veins. These discreet veins connect directly to the inferior vena cava.
Indirectly, yes. All veins flow back to either the superior vena cava or the inferior vena cava and into the heart.
capillaries of small intestine; superior mesenteric vein; hepatic portal vein; liver sinusoids; hepatic vein; inferior vena cava
Inferior Vena Cava, Superior Vena Cava, Pulmonary veins (left and right)
veins
Inferior vena cava
Inferior Vena Cava
The veins responsible for returning blood to the heart are the Superior and Inferior Vena Cava. Arteries send blood away from the heart, going from Arteries to Arterioles to Capillaries, then the return is from Capillaries to Venules to Veins. The Superior and Inferior Vena Cava are the veins that send blood to the right atrium after an entire blood circulation cycle.
Portal vein receives blood from two major veins, Superior mesenteric vein that drains the entire small bowel and splenic vein which drains the entire large bowel and spleen. Portal vein supplies about 60% of the total blood flow to the liver.
The two blood vessels that connect to the right atrium are the superiorvena cava (from the top half of the body) and the inferior vena cava (from the lower half of the body). They are both veins carrying unoxygenated blood back to the heart and subsequently, the lungs, to be oxygenated.
inferior vena cava
D. Inferior vena cava is not part of the splanchnic circulation. The splanchnic circulation includes the celiac artery, hepatic portal vein, and superior mesenteric artery, which supply blood to the digestive organs. The inferior vena cava returns blood from the lower body to the heart.