THE VESSEL IS THE MIDDLE HEPATIC VEIN.
The hepatic veins are the one that carry oxygen depleted blood from the liver into the inferior vena cava. They also transport blood that has been drained from the colon, pancreas, stomach and the small intestines. The hepatic veins are three in number, they are: right hepatic vein, middle hepatic vein and the left hepatic vein.
It is colder, BECAUSE:
As we go up in the atmosphere, air pressure continually becomes less. That means the rising<span> air is expanding. And a characteristic of any gas is that it is cooled by expansion. So the draft of warm air that starts </span>rising<span> from the earth's surface continually cools itself as it </span>rises<span>.
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Hope this answers your question!