| Which of the following cell types would be considered a rare finding in a direct bone marrow smear? | View Page |
| The M:E ratio represent the ratio of nucleated bone marrow cells with respect to: | View Page |
| Match each of the following: | View Page |
| These cells tend to occur in tight clusters. They may have prominent nucleoli, immature chromatin, and scant cytoplasm. | View Page |
| Location of Cells within Cord Within the hematopoietic cords each cell line has a specific location for development.
Erythroid precursors are located near a venous sinusoid and cluster around a macrophage. This is referred to as an erythroblastic island. Developing red cells obtain iron needed for hemoglobin production from macrophages.
Megakaryocytes are also located close to a venous sinus. They extend their cytoplasm in fingerlike projections through the sinus wall in order to release their platelets directly into the blood in the sinus.
Immature granulocytes lie within the hematopoietic cords.
The metamyelocyte stage is the first stage of the granulocyte series that is motile and able to move toward the sinus area. Mature neutrophils, eosinophils and basophils enter the sinusoidal blood through the basement membrane. As maturing erythrocytes also move toward the sinus wall any remaining nuclei are lost as the red cells move through small openings in the cells lining the sinus wall. | View Page |
| Promegakaryocyte The next stage after the megakaryoblast is the promegakaryocyte. It is intermediate in maturity between a megakaryoblasts and mature megakaryocytes. It may have multiple nuclei, coarse chromatin, and more cytoplasm than a megakaryoblast. | View Page |
| Examination of Wright-Giemsa Stained Bone Marrow Examination of Wright-Giemsa stained bone marrow preparation involves examination under low power (10X objective) high power (40-50X objective )and oil immersion (100X objective). Low power examination: Assess quality of smear, assess number of megakaryocytes.Assess myeloid to erythroid ratio.Evaluate morphology and do differential count. | View Page |
| Low Power Magnification This smear is shown under low power (10x objective) magnification. The reddish cells in the background are mature red blood cells. The dark dots are nucleated erythroid and myeloid precursors. The large dark dot in the middle is a megakaryocyte. Normally, about 5 to 10 megakaryocytes are seen per microscopic field at low power magnification. Clusters of megakaryocytes usually indicate megakaryocytic hyperplasia. Less than 2 megakaryocytes per low power field may mean megakaryocytic hypoplasia. | View Page |
| High Power Magnification This field under high magnification shows an increased number of megakaryocytes (megakaryocytic hyperplasia). This patient had thrombotic thrombocytopenic purpura. He was therefore consuming increased numbers of platelets, and his bone marrow was responding by increasing the number of megakaryocytes, which of course break up into platelets. | View Page |
| Megakaryoblast This slide shows an example of the youngest cell in the megakaryocyte series, the megakaryoblast. Megakaryoblasts have a fine chromatin structure with multiple nucleoli, and scant basophilic cytoplasm. Cytoplasmic tags are frequently seen. It may vary 20-50 microns in diameter. | View Page |
| Megakaryocyte The next stage is the fully developed megakaryocyte. It typically shows nuclear divisions and abundant very granular cytoplasm. Megakaryocytes are the largest cell found in normal bone marrow and can range in size from 30-100 microns. The nuclear chromatin pattern is coarse. Nucleoli are absent. | View Page |
| Meta Megakaryocyte Stage The next stage is the meta megakaryocyte. By this point, platelets are actually breaking away from the meta megakaryocyte cytoplasm. The example shown in this slide illustrates the platelets forming and breaking away near the arrow. | View Page |
| Other Large Cells It is also important to scan the slide for the presence of other large cells which are not usually seen in normal marrow. An osteoclast is an example of this type of cell. Osteoclasts are large multiinucleated cells (up to 100 microns) which may be confused with megakaryocytes. One striking difference is that an osteoclast has multiple nuclei which are separate from each other. The multiple nuclei in the megakaryocyte are joined together. The cytoplasm, although somewhat finer in texture, could be mistaken for platelets. | View Page |
| Please identify the cell in this image. | View Page |
| Please identify the cells present in this image? | View Page |
| Megakaryocyte Morphology It is also important to examine the morphology of platelets. One megakaryocyte shows a single nucleus surrounded by cytoplasm which will eventually break off to form platelets. The other one at the arrow shows a lobated nucleus which has divided several times; the large amount of cytoplasm surrounding this nucleus means that this cell will be able to produce more platelets. In general, as the megakaryocyte gets older, it forms more nuclear lobes, more cytoplasm and therefore is able to produce more platelets. | View Page |
| Bare Nucleus Megakaryocyte. Rarely, the bare nucleus is visible after the platelets have been shed. It is referred to as a bare nucleus megakaryocyte. | View Page |
| Please identify the cell in this image? | View Page |
| Nuclear Division in Megakaryocytes Megakaryocytes differ from other cell lines because the nucleus divides during mitosis but the cytoplasm does not. | View Page |
| Platelet Kinetics Platelets are derived from the cytoplasm of megakaryocytes, giant cells in the bone marrow. At any given time, two thirds of the total platelets are in the circulation and one third are present in the spleen. In persons with enlarged spleens 80-90% of the platelets are in the spleen resulting in a decreased concentration of circulating platelets. In individuals who have had a splenectomy all of the platelets will be in the circulating blood. The life span of the platelet is 8-10 days. | View Page |
| Glossary of Terms A through M. Antibody - A modified type of serum globulin synthesized by lymphoid tissue in response to antigenic stimulus. By virtue of specific combining sites each antibody reacts with only one antigen. Anucleate - Having no nucleus. Azurophilic granules - The well-defined large reddish granules (lysosomes) which may be present in large lymphocytes. They are called "azurophilic granules" because they stain blue with the azure stains which were originally used. Basophilic granules - Specific granules present in the cytoplasm of basophils. These granules are large and stain purple-black due to their strong affinity for basic stain. B-cell - Bone marrow derived lymphocytes which produce humoral antibodies. Biconcave - Having two concave surfaces. Cellular Immunity - The capacity of a small proportion of lymphoid population to exhibit response to a specific antigen. Chromomere - The centrally located granular portion of the platelet. Clone - A population of cells descended from a single cell. Delayed Hypersensitivity - (part of cellular immunity) that develops slowly over a period of 24-72 hours after an antigenic stimulus. It consists of an accumulation of cells around small vessels and/or nerves. Example: Tuberculin skin test reaction. Digestive Enzyme - A substance that catalyzes or accelerates the process of digestion. Eosinophilic Granules - Specific granules present in the cytoplasm of eosinophils. These granules are large, refractile spheres which stain reddish-orange due to their strong affinity for acid stain. Erythrocyte (red blood cell, RBC) - One of the elements found in peripheral blood. Normally the mature form is a non-nucleated, circular, biconcave disk adapted to transport respiratory gases. Fixed Macrophage - A phagocyte that is non-motile. Free Macrophage - An ameboid phagocyte present at the site of inflammation. Graft Rejection - A transplanted tissue that is rejected by the body's antibodies. Graft vs. Host Reaction - A complication that occurs when an implanted piece of tissue, which contains antibodies, rejects the host's tissue. Granulocyte - A leukocyte which contains granules in its cytoplasm, i.e., neutrophilic, eosinophilic, or basophilic granules. Half-life - is the length of time it takes for half of the cells circulating at a given time to leave the blood for the tissues. Hemocyte - Any blood cell or formed element of the blood. Hemostasis - A mechanism of the vascular system to arrest an escape of blood. It involves an interaction between blood vessels, platelets, and coagulation. Heparin - A mucopolysaccharide acid which, when present in sufficient amounts, functions as an anticoagulant by inhibiting thrombin. Histamine - A powerful dilator of capillaries and a stimulator of gastric secretions. Humoral Immunity - Acquired immunity produced after response to an antigenic stimulus in which B cells produce circulating antibodies. Hyalomere - the clear, blue non-granular zone surrounding the chromomere of a platelet. Immune Response - The interaction of a cell and an antigen that results in a proliferation of the cell and a capacity to produce antibodies. Isotonic Fluid - A fluid whose elements have an equal osmotic pressure. Leukocyte (white blood cell, WBC) - One of the formed elements of the blood; involved primarily with the body's defense. Lysosome - A microscopic body within cell cytoplasm; contains various enzymes, mainly hydrolytic, which are released upon injury to the cell. Megakaryocyte - A giant cell of the bone marrow from which platelets are derived. Mononuclear - A cell having a single nucleus. | View Page |