Bone Marrow

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  1. Bone marrow
    • tissue enclosed by bone (cortical and cancellous)
    • hematopoietic cells, adipose tissue and supportive tissue
    • red and yellow (all red early in life)
  2. Red bone marrow
    • hematopoiesis.  
    • All is red in young animal, turns yellow with age.  
    • Adults, can be found in proximal humerus, femur, sternum, ribs, vertebral bodies
  3. yellow bone marrow
    mainly fatty tissue, no hematopoietic function.  Can turn red if needed.
  4. Hematopoietic cells
    • precursers to cells found in blood or tissue
    • includes cells in mitotic (proliferation) pool and post-mitotic (maturation) pool
    • Includes erythrocytes, leukocytes, megakaryocytes
  5. Things you can learn from bone marrow
    • Hematologic abnormalities (nonregenerative anemia, penias, persistent cytosis', abnormal blood cell morphology, unexplained presence of immature cells and regenerative or not in a horse.)
    • What stage cancer is in (Lymphoma, mast cell tumors)
    • Blood chemistry abnormalities (hyperglobulinemia, hypercalcemia)
  6. aspirate vs. biopsy
    • aspirate is easier/faster/cheaper (just stain and examine)
    • biopsy cuts a solid core of marrow, has to be fixed, decalcified, embedded, sectioned and stained prior to examination by a pathologist.  More accurate evaluation.
  7. Contraindications
    • don't use in patients with bleeding problems (hemostatic diathesis).  Could be hemorrhage.
    • Ribs and sternum of horse can lead to hemothorax or cardiac tampanade (pressure on heart)
    • Post biopsy infection
  8. Where to perform bone marrow aspirate in dog
    • proximal humerus
    • Trochanteric fossa of proximal femur
    • iliac crest
  9. Where to perform bone marrow aspirate in cat
    Proximal femur and proximal humerus
  10. Where to perform bone marrow aspirate in horse, cow, camel
    Ilium, ribs, sternum
  11. Technique of bone marrow aspirate
    • General anesthesia or sedation, local anesthetic (both skin and periosteum)
    • skin incision
    • needle cuts through muscle
    • Rotate needle into bone
    • remove stylet
    • attach syringe, pull back just until you see marrow (release quickly to avoid blood contamination)
    • prepare smears immediatly
  12. Slide preparation
    • drop of marrow, spread with another slide
    • place vertically on absorbant surface to further remedy blood contamination
    • air dry, stain with Romanowsky (Wright-type)
  13. Core biopsy
    Jamshidi needle, stylette, shepherds crook
  14. Order of erythropoeisis
    • Rubriblast
    • prorubricyte
    • rubricyte
    • metarubricyte
    • prolychromatophilic erythrocyte (reticulocyte)
    • mature erythrocyte
  15. Rubriblast
    most immature recognizable RBC
  16. Prorubricyte
    between rubriblast and rubricyte.  Cytoplasm more abundant and blue
  17. rubricyte
    between prorubricyte and metarubricyte.  Most mature stage where mitosis can occur
  18. metarubricyte
    most mature RBC that contains a nucleus
  19. Polychromatophilic erythrocyte
    reticulocyte.  Anucleated, blue-pink, larger than RBC
  20. Erythroid maturation facts
    • get smaller
    • nuclei gets smaller, chromatin clumps
    • nucleus extruded
    • cytoplasm goes from blue-grey to orange-red as RNA is lost
    • reticulocytes and RBCs migrate
    • Takes 3-5 days.
  21. Erythropoietin
    released from kidney in response to hypoxia.  Stimulates stem cell differentiation into rubriblast.  High enough concentration shortens marrow transit time and graduates early
  22. Hormones that promote erythropoiesis
    androgens, glucocorticoids, insulin, growth hormone, thyroid hormone
  23. hormones that inhibit erythropoiesis
  24. Granulocyte
    • Polymorphonuclear leukocytes (PMNs)
    • Includes all three granules--neutrophils, basophils, eosinophils
  25. Granulocyte (myeloid) maturation
    • Same for neutrophil, basophil and eosinophil
    • myeloblast
    • progranulocyte (promyelocyte)
    • myelocyte (first differentiation)
    • metamyelocyte
    • band granulocyte
    • segmented granulocyte
  26. myeloblast
    earliest recognizable myeloid cell. No granules.  Before promyelocyte (progranulocyte)
  27. Progranulocyte (promyelocyte)
    • slightly larger than precurser myeloblast.  Also larger than follower myelocyte
    • Nucleus is central or on one side (eccentric)
    • cytoplasm has primary granules.
  28. myelocyte
    • smaller than precurser promyelocyte, larger than metamyelocyte.  
    • Last mitosis
    • primary granules replaced by secondary (specific) granules
  29. metamyelocyte
    • smaller than precurser myelocyte, larger than follower band granulocyte.  
    • kidney shaped indention in nucleus.  Secondary granules.
  30. band granulocyte
    • smaller than metamyelocyte, larger than segmented granulocyte.  
    • U-shaped or deeply indented nucleus.  Secondary granules
  31. segmented granulocyte.
    smaller than band.  Lobulated or markedly constricted nuclei, secondary granules.
  32. Monocytes in bone marrow
    • difficult to differentiate because nucleus can look like anything and resembles myeloid series.
    • monoblast, promonocyte, monocyte in bone marrow
  33. Megakaryocyte
    • large multinucleated cell whose cytoplasmic fragments become platelets.
    • megakaryoblast, promegakaryocyte (nucleus separates), megakaryocyte.
  34. Cells seen in bone marrow
    • RBC, monocytes, neutrophils
    • lymphocytes (small)
    • plasma cells (differentiated lymphocyte that produces hemoglobin)
    • lymphoblast (rare, lymphoproliferative disorders)
    • macrophages, osteoblasts, osteoclasts,
  35. Osteoblasts
    similar to plasma cells in appearance.  In young animals and those with bone remodeling (fracture)
  36. osteoclasts
    • large multinucleated cell with nucleus separated.  
    • phagocytize bone.  
    • rare.
  37. Mast cell
    • easily recognized.  
    • normally present in very low concentration, rare in marrow.
  38. Fibrocytes and Fibroblasts
    seen infrequently because don't exfoliate easily.
  39. Bone marrow evaluation
    • scan: whole slide for heterogenous and overall cellularity
    • erythroid.  
    • cellularity: (25-75% cells), otherwise hyper- or hypocellular.  Decreases with age.  Increases with need.  
    • Maturation/morphology: of RBC and WBC (complete, orderly, increase in # with each stage of development
    • Myeloid  to Erythroid ratio (M:E): examine 500 cells, granulocytic/nRBC (hemodilution a problem)
    • Reticulocyte couont in horses
  40. M:E ratio
    myeloid to erythroid ratio.  normal is anywhere form 0.5:1 to 3:1.  Interpret in light of CBC.
  41. What should you see most of in bone marrow?
    mature cells, due to mitosis
  42. High M:E ratio indicates
    high level of granulocytes or low level of erythrocytes
  43. Low M:E ratio indicates
    low level of granulocytes or high level of erythrocyes
  44. reversible stem cell disorders of marrow
    • transient, usually stem cell recovers (if no complications)
    • Initial neutropenia, thrombocytopenia and nonregenerative anemia may follow if disorder lasts for 1-2 weeks.  
    • Caused by viral (F. panleukopenia or parvo), drugs (like chemo), chemicals
  45. irreversible stem cell injury in marrow
    • irreversible, cause not always understood.  Can be chemicals or radiation, or FeLV.  
    • 4 types.  Aplasia or hypoplasia, myelodysplasia, myeloproliferative disease, myelodysplasia becoming cancer.
  46. 4 types of irreversible stem cell injury
    • aplasia or hypoplasia (absent or insufficient production)
    • myelodysplasia (abnormal development)
    • myeloproliferative disease (neoplastic production)
    • myelodysplasia progressing into neoplasia over time.
  47. Aplasia
    • irreversible stem cell injury with hypocellular to acellular marrow.  
    • Presents with selective, severe and nonregenerative anemia or pancytopenia (nonregen anemia includes thrombocytopenia and neutropenia)
    • Red cell aplasia in dogs likely immune mediated.
  48. myelodysplasia
    • abnormal development with variable manifestations of subtle, morphological changes in blood cells.  
    • Usually includes some kind of cytopenia (neutropenia, nonregenerative anemia, thrombocytopenia)
    • Most common in cats, very rare in others
  49. Myelofibrosis
    • scarring of bone marrow, develops in response to marrow injury.  
    • Can be caused by anything toxic to hematopoietic cells--damages microvasculature and leads to necrosis and fibrosis (dying and scarring)
  50. myeloproliferative and lymphoproliferative disorders (leukemias)
    • neoplastic proliferation of hematopoietic cells within marrow.  
    • Neoplastic cells found in peripheral blood or bone marrow.
  51. myeloproliferative neoplasia
    neoplasms derived from bone marrow erythrocytes, granulocytes, monocytes and megakaryocytes.  (monocytic leukemia, eosinophilic leukemia, etc.)
  52. lymphoproliferative neoplasia
    • neoplasms from lymphocytes or plasma cells.  
    • More immature than mature cells is bad.  
    • ex. acute lymphoblastic leukemia, chronic lymphocytic leukemia, plasma cell myeloma.
  53. Acute leukemias
    • Infiltration and replacement of marrow by blast cells that proliferate but do not mature or function in any useful way.  
    • any hematopoietic cell line can be involved.  
    • progression is rapid (death within days or weeks without bone marrow transplant)
  54. chronic leukemias
    • some infiltration of marrow.  Malignant cells mature partially and retain some function.  
    • Affected can survive months to years with little/no treatment.  Don't notice right away, much better prognosis.
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Bone Marrow
Bone Marrow, Clinical laboratory techniques lecture
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