Blood carries immune system cells, known as white cells or leukocytes. Some examples of white cells are phagocytes and lymphocytes.
Phagocytes ingest and dissolve pathogens, as well as strange particles or dying cells.
Lymphocytes are divided into T cells, B cells, and natural killer cells (NK). B cells produce antibodies to respond to foreign cells, T cells attack pathogens using enzymes and other non-antibodies responses, while NK cells combat tumors and cells infected by viruses.
Apples are drawn to a massive object, like the earth, and fall down under a gravitational constant. On the other hand, planets revolve around a more massive object under the same premise. It’s the same idea, just one follows a linear path, and the other has a uniform circular motion path because other forces are acting on it. In other words, the planets ARE still falling, but the sun is also pulled by them so they just keep dancing.
