Why do veins have valves?

What are the formed elements (cell or parts of cell) in blood and what are their functions ?

Ateam from new york presbyterian hospital is conducting a study about a recent increase in cases involving both excess sweating and kidney stones. what would the team need before it draws a conclusion about the cases? medications that are specifically designed to treat the sickness machines that are built to process blood and reduce symptoms until patients are healthy again data that profile the various patients who report these symptoms proof that the excess sweating is related to the excessive kidney stones

Long-period comets come from the oort cloud particles in earth’s atmosphere material from the asteroid belt the kuiper belt