Neutrophils of several species have more distinct, eosinophilic granules and are called heterophils. Rabbits, guinea pigs, rats, reptiles, fish and birds have heterophils. Neutrophils are highly-differentiated cells which cannot divide. They have abundant cytoplasmic glycogen stores and cellular respiration is primarily by anaerobic glycolysis. This form of respiration allows the neutrophil to maintain effective function in hypoxic necrotic tissue and exudates.
Neutrophils originate from stem cells in the bone marrow.
Following maturation, they remain in a storage pool in the bone marrow for approximately 1.5 days. There are almost five times more neutrophils in the storage pool than the circulating blood, and these act as a reservoir for periods of high demand. Neutrophils circulate in the peripheral blood for approximately 12 hours. Following emigration into tissues, neutrophils live for about 2 days. If the emigration was in response to an inflammatory stimulus, the tissue life span can be greatly shortened.