Under normal circumstances, the proportion of blood to body weight is about 7~8%. Blood can be divided into plasma and blood cells. 1. Plasma: mainly composed of water and a variety of electrolytes, but also includes certain small molecules of organic compounds, gases, etc. Plasma contains a variety of proteins, such as albumin, globulin, fibrinogen, which is important for the maintenance of plasma colloid osmotic pressure. 2. Blood cells: including red blood cells, white blood cells, platelets, red blood cells, the most white blood cells, the least. Under normal circumstances, the number of erythrocytes is about (4000~5500)×10⁹/L; the number of leukocytes is about (4~10)×10⁹/L, including neutrophils, eosinophils, basophils, monocytes, and lymphocytes; the number of platelets is about (100~300)×10⁹/L; and the number of platelets is about (100~300)×10⁹/L. The number of platelets is about (100~300)×10⁹/L. ⁹/L.