Hematopoiesis Flashcards
What is myeloid tissue?
Tissue that actively produces erythrocytes, platelets, and leukocytes
What is present in the myeloid tissue?
Developing blood cells suspended in a loose connective tissue stroma and large sinusoids with macrophages
Are stem cells present in myeloid tissue?
Yes, blood cells are a continuously renewing cell population
How is myeloid tissue distributed in the fetus?
In the adult?
Fetus: All bone marrow is actively hemopoietic, and hemopoiesis also occurs in liver, kidney and spleen
Adutl: Some bone marrow is hemopoietic (pelvis, sternum, ribs, vertebrae, cranial bones, femur, humerus) and during times of severe need for blood cells, fatty marrow is converted to hemopoietic marrow and extramedullary hemopoiesis occurs (liver, spleen, kidney)
What are the hemopoietic cell populations?
Stem cells, progenitor cells, maturing cells, stromal cells
What are stem cells
totipotent or pluripotent and capable of self renewal
What are progenitor cells
Committed cells for a specific lineage. Colony forming units
What are maturing cells
Cells that result from differentiation from progenitor cells
What are pluripotent stem cells?
Develop in the mesenchyme associated with the fetal yolk sac (liver first, spleen and bone marrow, then kidney)
Circulate in very small numbers in adult peripheral blood and resemble lymphocytes
Describe the maturation of blood cells
As differentiation progresses cells become smaller, nucleus becomes smaller and heterochromatic
RBC cytoplasm changes from basohilic to pale eosinophilic
For granulocytes, specific granules appear in the cytoplasm
Tell tale signs a cell is not a RBC
any degree of non-round nucleus
Granules in cytoplasm
What is a rubriblast
1st stage erythrocyte
Large, deeply basophilic, no cytoplasm
What is a prorubricyte
More cytoplasm and less vesicular than rubriblast
What is a rubricyte
Mottled nucleus and cytoplasm (both basophilic and acidophilic)
Heterochomratic nucleus
What is a metarubricyte?
Close in size to RBC, nucleus is dense and round
Cytoplasm is basophilic
What is a reticulocyte
No nucleus
Close in size to RBC, slightly bigger
Cytoplasm is gray-ish, slightly more basophilic than RBC, clumps of ribosomes may be visible
Circulates in very smal number (only precursor that is normal in peripheral blood)
Causes of anemia
Reduction in RBC number, hemoglobin content or both
Most common hematologic disorder
Symptom, not disease due to blood loss, hemolysis, decreased RBC production
What is regenerative anemia?
Marrow responds by releasing immature RBCs
Reticulocyte count goes up (best indicator of regeneration)
Mean corpuscular volume goes up and mean corpuscular hemoglobin concentration goes down (because reticulocytes have less hemoglobin)
What is granulocytopoiesis
Stages of granulocyte development
Cels become smaller as they mature, the nucleus is round early and becomes indented or multi-nucleated
Abundant cytoplasm granules
Myeloblast characteristics
Larger than rubriblast
More cytoplasm
Characteristics of promyelocyte
Non-specific granules first appear
Characteristics of myelocyte
Nucleus is round or oval, specific granules appear (eosinophilic granules, basophilic granules, neutrophil granules respectively)
Characteristics of metamyelocyte
Nucleus becomes bean shaped (indented less than 1/2 diameter of nucleus)
Characteristics of band cell
Horseshoe nucleus
The indentation goes more than halfway across the nucleus
Which blood cell has the most lobulated nucleus
Neutrophil
Which granulocytes share the same color granules with a Wright’s stain?
Basophils and mast cells
What does the total neutrophil count reflect?
the balance between marrow production, release in to circulation, and tissue demand
What is a left shift in neutrophil dynamics?
Regenerative if associated with neutrophilia
degenerative without neutrophilia (or with neutrophenia [toxic]) or if there are more nonsegmented cells than mature cells
What are thrombocytopoiesis stages
Megakaryoblast: Very large ovoid nucleus with nucleoli
Promegakaryocyte (don’t worry): Divided nuclei
Megakaryocyte: Large cell with multilobed, heterochromatic nucleus
Basophilic or acidophilic cytoplasm
Platelets detach at periphery
Where are megakaryocytes usually found?
Near a sinusoid with other hemopoietic tissue
