Veins take blood back to the heart. which gas would be most abundant in a vein that takes blood from muscle cells in the arm back to the heart?
carbon dioxide
oxygen
nitrogen
hydrogen

The right answer is carbon dioxide.

In anatomy, a vein is a blood vessel that allows the transport of blood from the periphery (organs or tissues) to the heart (venous return):

* from the lungs to the heart: the pulmonary veins carry blood rich in oxygen so that it is redistributed in the body in the systemic circulation.

* from the other organs (like the muscle in the arm) to the heart: the other veins carry oxygen-depleted and carbon dioxide-rich blood so that it is reoxygenated by the lungs into the pulmonary circulation.

[content deleted] - user123802726recklesschicken

americans began to notice growing differences between the northern and southern sections of the country. there were more people living in cities in the north, which made it more urban. more people lived on farms in the south, which made it more rural. while many people were farmers in the northern states, there were now other ways to make a living, such as working in mechanical cotton gins factories manufacturing cloth, tools and other goods. people in the north supported high tariffs on goods imported from europe because the extra cost encouraged people to “buy american” instead. in the southern states, planters did not like tariffs because they sold most of their production to europe and bought their tools from there as well. southerners believed the protective tariff was something that only northern factory owners keep their profits high. so the southern politicians came up with an idea. they would opt out. they would simply ignore the protective tariff. it was ‘null and void’ in south carolina. the state would not collect the taxes on goods imported into south carolina, no matter what the president said they had to do. this decision led to the nullification crisis.