1. Why do you have a dedicated circulation pathway for the spleen, stomach, pancreas, gallbladder, and intestines that passes through the liver

Because the liver is a crucial organ that processes the nutrients that the blood carries. Also, we storage blood when the volume of it is above the normal levels.                

Explanation:

The blood that circulates through the spleen, stomach, pancreas, gallbladder, and intestines has to pass through the liver. This organ will metabolize proteins, lipids, cholesterol, bilirubin, toxins, and steroid hormones, also store glycogen, fats, Ferrum, and vitamins, and produce bile. The nutrients that the blood carries are processed in the liver to keep the body healthy and to eliminate substances through bile. The bile will also help with the digestion of nutrients in the intestine.

When the blood from these organs (spleen, stomach, pancreas, gallbladder, and intestines) goes to the liver via the hepatic vein, the hepatic cells process it and deals with the functions previously mentioned. Once that blood is filtered, it goes to the hepatic veins, and from there, to the heart.