WSU_1_007: Equine Blood
The leukocytes (white blood cells) are commonly divided into the polymorphonuclear cells (PMNs) or granulocytes and the mononuclear cells. The PMNs or granulocytes have segmented nuclei (hence, polymorphonuclear = many shaped nucleus) and contain primary lysosomal granules.
The neutrophils, eosinophils and basophils fall into this group. The basophils contain basophilic granules, the eosinophils contain acidophilic (eosinophilic) granules, and the neutrophils contain granules which stain neutral, neither strongly basophilic or acidophilic. Actually, sometimes the granules in neutrophils stain faintly acidophilic.
Monocytes, which become macrophages in the tissue, and lymphocytes are mononuclear cells. Monocytes are tricky in that they have a pleomorphic nucleus, sometimes appearing lobed, and you may see lysosomal vacuoles. Actually, monocytes contain many primary lysosomes - they just are not always visible.
The "formed" elements of blood include erythrocytes and platelets. Erythrocytes are not true cells in mammals because they discharge their nucleus before entering circulation. Likewise, in mammals, platelets do not have nuclei as they are merely cytoplasmic fragments of megakaryocytes.
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[WebSlide] Blood_WSU; Blood Smear (WSU_1_007)