DEFENSE

Leukemic cells are transported by blood to locations where foreign invaders are present. These cells help sustain an animal’s health by supporting its immune system. By deliv­ering platelets to the sites of vascular damage, blood aids in haemostasis and prevents excessive bleeding in the animal.

6.6.1 Composition of Blood in Animals

Red blood cells, white blood cells, and platelets are formed elements combined with blood plasma, a liquid, to form blood, a connective tissue. The erythrocytes make up the largest population of all the cellular components, followed by platelets, and white blood cells, which make up the smallest. Basophils are the least common cell type, fol­lowed by eosinophils and monocytes, according to the dif­ferential leucocyte count. In carnivores and omnivores, the population of neutrophils exceeds that of lymphocytes; in ruminants, however, the opposite is true (Figure 6.1).

6.7