The chromatin of the neutrophil has a characteristic arrangement. Wide regions of heterochromatin are located chiefly at the periphery of the nucleus in contact with the nuclear envelope. Regions of euchromatin are located primarily at the center of the nucleus with relatively smaller regions contacting the nuclear envelope (Fig. 10.5). In women, the Barr body (the condensed, single, inactive X chromosome) forms a drumstick-shaped appendage on one of the nuclear lobes.
Neutrophils contain three types of granules.
The cytoplasm of a neutrophil contains three kinds of granules. The different types of granules reflect the various phagocytotic functions of the cell.
 Specific granules (secondary granules) are the smallest granules and are at least twice as numerous as azurophilic granules. They are barely visible in the light microscope; in electron micrographs, they are ellipsoidal (see Fig. 10.5). Specific granules contain various enzymes (i.e., type IV collagenase, phospholipase) as well as complement activators and other antimicrobial peptides (i.e., lysozymes, lactoferrins).
 Azurophilic granules (primary granules) are larger and less numerous than specific granules. They arise early in granulopoiesis and occur in all granulocytes, as well as in monocytes and lymphocytes. The azurophilic granules are the lysosomes of the neutrophil and contain myeloperoxidase (MPO) (a peroxidase enzyme), which appears as a finely stippled material with the TEM. Myeloperoxidase helps to generate highly reactive bactericidal hypochlorite and chloramines. In addition to containing a variety of the typical acid hydrolases, azurophilic granules also contain cationic proteins called defensins, which function analogously to antibodies and the antimicrobial peptide cathelicidin to kill pathogens.
 Tertiary granules in neutrophils are of two types. One type contains phosphatases (enzymes that remove a phosphate group from a substrate) and is sometimes called a phosphasome. The other type contains metalloproteinases, such as gelatinases and collagenases, which are thought to facilitate the migration of the neutrophil through the connective tissue. Aside from these granules, membrane-bounded organelles are sparse. A small Golgi apparatus is evident in the center of the cell, and mitochondria are relatively few in number (see Fig. 10.5).
Neutrophils are motile cells; they leave the circulation and migrate to their site of action in the connective tissue.
An important property of neutrophils and other leukocytes is their motility. Neutrophils are the most numerous of the first wave of cells to enter an area of tissue damage. Their migration is controlled by the expression of adhesion molecules on the neutrophil surface that interact with corresponding ligands on endothelial cells (Fig. 10.6) and are often involved in cell binding.
The initial phase of neutrophil migration occurs in the post-capillary venules and is regulated by a mechanism involving neutrophil–endothelial cell recognition. Selectins (a type of cell adhesion molecule) on the surface of the circulating neutrophil (CD62L) interact with receptors (GlyCAM-1) on the surface of the endothelial cells. The neutrophil becomes partially tethered to the endothelial cell as a result of this  FOLDER 10.3 Clinical Correlation: Hemoglobin Disorders