![]() Neutrophils, the most numerous leukocytes, are phagocytic and have light-colored granules. Monocytes and lymphocytes are agranulocytes. Neutrophils, eosinophils, and basophils are granulocytes. The cells that develop granules in the cytoplasm are called granulocytes and those that do not have granules are called agranulocytes. There are two main groups of leukocytes in the blood. Leukocytes are able to move through the capillary walls into the tissue spaces, a process called diapedesis.In the tissue spaces they provide a defense against organisms that cause disease and either promote or inhibit inflammatory responses. Some are phagocytic, others produce antibodies some secrete histamine and heparin, and others neutralize histamine. They use the blood as a transport medium. Even though they are considered to be blood cells, leukocytes do most of their work in the tissues. Leukocytes, or white blood cells, are generally larger than erythrocytes, but they are fewer in number. The primary function of erythrocytes is to transport oxygen and, to a lesser extent, carbon dioxide. The shape provides a combination of flexibility for moving through tiny capillaries with a maximum surface area for the diffusion of gases. Erythrocytes are tiny biconcave disks, thin in the middle and thicker around the periphery. ![]() Erythrocytes (red blood cells)Įrythrocytes, or red blood cells, are the most numerous of the formed elements. The three classes of formed elements are the erythrocytes (red blood cells), leukocytes (white blood cells), and the thrombocytes (platelets). The formed elements are cells and cell fragments suspended in the plasma. Various compounds, including proteins, electrolytes, carbohydrates, minerals, and fats, are dissolved in it. It transports nutrients as well as wastes throughout the body. The watery fluid portion of blood (90 percent water) in which the corpuscular elements are suspended. The white blood cells and platelets form a thin white layer, called the " buffy coat", between plasma and red blood cells. The light yellow colored liquid on the top is the plasma, which accounts for about 55 percent of the blood volume and red blood cells is called the hematocrit,or packed cell volume ( PCV). Because the formed elements are heavier than the liquid matrix, they are packed in the bottom of the tube by the centrifugal force. When a sample of blood is spun in a centrifuge, the cells and cell fragments are separated from the liquid intercellular matrix. Here, an optical platelet count and peripheral blood smear were critical in making the timely diagnosis of a life-threatening disease.Acknowledgements Composition of the Blood Despite prompt treatment, the patient suffered cardiac arrest during plasma exchange and died.The impedance method derives the platelet count from a continuous platelet/RBC histogram, which renders it susceptible to miscounting RBC fragments as platelets. Platelet count by the optical method was 20 × 10 9/L, and the correct diagnosis of thrombotic thrombocytopenic purpura was made and subsequently confirmed with undetectable ADAMTS13 activity and an anti-ADAMTS13 antibody. A peripheral blood smear (panel E original magnification ×40 May-Grünwald-Giemsa stain) showed no malarial parasites but did show striking red cell changes, with polychromasia, florid fragmentation, microspherocytes, and severe thrombocytopenia. Importantly, although the platelet count by the impedance method seemed normal, the histograms were abnormal, with the presence of large particles in the platelet window (indicated by the black arrow in panel A panel B, normal platelet count) and small particles in the red blood cell (RBC) window (indicated by the black arrow in panel C panel D, normal platelet count). There was also evidence of hemolysis (reticulocytosis, high lactate dehydrogenase, and hyperbilirubinemia) which, along with his history, was suggestive of severe malaria with blackwater fever. A complete blood count showed hemoglobin of 73 g/L, white blood count of 14.7 × 10 9/L, and platelets 266 × 10 9/L. Category: Laboratory Hematology > Basics of automated cell counts > Causes of inaccurate platelet countsĪ 37-year-old man who had recently been treated for malaria while in Kenya presented with ongoing fevers and malaise as well as new headaches and hematuria.
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