Asteroids are celestial rocky bodies that orbit the sun. It was Sir William Herschel who first coined the term âasteroidâ (Greek for star-like) in 1802. He thought that Ceres and Pallas, discovered in 1801 by Giuseppe Piazzi and Heinrich Olbers respectively, were too small and were remnants of a destroyed planet.
blood cell. n. Any of the cells contained in blood; an erythrocyte or leukocyte; a blood corpuscle. blood cell. n. (Physiology) any of the cells that circulate in the blood. See erythrocyte, leucocyte.
White blood cells, or leukocytes, are cells of the immune system involved in defending the body against both infectious disease and foreign materials. There are several different types of white blood cells. They all have many things in common but are all distinct in form and function. They are produced in the bone marrow by hemopoeitic stem cells, which differentiate into either lymphoid or myeloid progenitor cells.