Red blood cell being dissolved in body fluid) was an important step in the evolution of vertebrates as it allows for less viscous blood, higher concentrations of oxygen, and better diffusion of oxygen from the blood to the tissues. The size of red blood cells varies widely among vertebrate species; red blood cell width is on average about 25% larger than capillary diameter, and it has been hypothesized that this improves the oxygen transfer from red blood cells to tissues. The red blood cells of mammals are typically shaped as biconcave disks: flattened and depressed in the center, with a dumbbell-shaped cross section,
White blood cell underlying cause, though the cause may not always be found. The complete blood cell count is a blood panel that includes the overall WBC count and various subsets such as the absolute neutrophil count. Reference ranges for blood tests specify the typical counts in healthy people. TLC- (Total leucocyte count): Normal TLC in an adult person is 6000-8000WBC/mm^3 of blood. DLC- (Differential leucocyte count): Number/ (%) of different type of leucocyte in per cubic mm. of blood. White blood cell White blood cells (also called leukocytes or leucocytes and abbreviated as WBCs) are the cells of the immune system that