Blood and blood vessels Blood

Blood circulates through the vessels, bringing oxygen and nourishment to all cells and carrying away waste products. The total adult blood volume is about

5 liters. Whole blood can be divided into two main components: the liquid portion, or plasma (55%), and formed elements, or blood cells (45%).

Plasma is about 90% water. The remaining 10% contains nutrients, electrolytes (dissolved salts), gases, albumin (a protein), clotting factors, antibodies, wastes, enzymes, and hormones. A host of these substances are tested for in blood chemistry tests. The blood cells are erythrocytes, or red blood cells; leukocytes, or white blood cells; and platelets, also called thrombocytes. All blood cells are produced in red bone marrow. Some white blood cells multiply in lymphoid tissue as well.