Blood Under the Microscope

normal blood smearSince my books are named Murder under the Microscope and Too Much Blood, how about we look at blood, under the microscope?
Blood is composed of plasma and cells. Plasma is pretty boring, but the cells …ah, they’re another thing entirely. Beautiful to look at, delightful to behold.
Blood cells are made in the bone marrow. In the fetus and newborn, nearly every bone in the body is involved, but after that, it’s pretty much limited to the ribs, sternum, vertebrae, and hipbones.bone marrow H&E_edited-1 That’s why, when a patient has a bone marrow aspiration, it’s done either in the sternum or hip.
The process of blood cell production is called hematopoiesis. There are three types of cells made in the bone marrow: RBC precursors in marrowerythroid precursors in marrow_edited-1nucleated RBCerythroid, or red cells; myeloid precursors in marrow_edited-1myeloid, or white cells; megakaryocyte_edited-1and megakaryocytes, which make platelets.
Red cells carry hemoglobin, which binds oxygen from the lungs and releases it to the tissues of the body.
White cells fight infection.
Platelets help blood to clot when there’s an injury, so that one doesn’t bleed to death from every little cut or scrape.
The precursors to these cells live in the bone marrow, and are not supposed to be present in the blood. However, when things go wrong, there’s no telling what may show up there. The pathologist is sometimes called upon to review blood smears, and sometimes can give clues to the patient’s doctor as to what may be going on there. It’s like a detective gathering clues to solve a crime.
Only instead of murder, the crimes here are called things like anemia, polycythemia, leukopenia, leukocytosis, thrombocytopenia, thrombocytosis, and the mother of them all, pancytopenia. Then there are myelodysplastic syndromes, and myeloproliferative syndromes, and leukemias.
There is another type of cell found in the blood, but these cells are made in the lymph nodes, or other lymphoid tissue in the body. They fight infection too, by making antibodies. But they can also cause crimes against the body, that are called lymphomas. And they can affect the bone marrow too, to cause leukemias. Or just to interfere with its function by taking up too much space.
Pathologists are often called upon to look at a blood smear to evaluate the lymphocytes in the blood, and decide whether they represent leukemia, or just reactive change, say to something like infectious mononucleosis. Here’s an example of normal and reactive lymphocytes.blood smears
There is so much to talk about when discussing blood disorders that it’s way too much for just one blog.
So stay tuned to this station. There will be more blogs on this utterly fascinating subject.

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