Hematopoiesis Flashcards
Red marrow
Network of vascular sinuses (specialized blood vessels) & hematopoietic cells.
Organized into sacs (alveoli) within which hematopoietic cells develop in nests or foci.
Supported by reticular cells and reticular fibers.
In red marrow, cells meant to become RBCs develop ___ the sinus wall in nests with an associated macrophage which contains iron.
Megakaryocytes (makes platelets) develop ___ the sinus
Cells meant to become granulocytes develop ___ the sinus.
RBC & megakaryocytes - near the sinus
Granulocytes - away from the sinus
Yellow marrow is filled with ____ and essentially excludes ____.
Where is it?
Filled with adipocytes and excludes hematopoietic cells.
Housed in the diaphysis of long bone
Erythropoiesis stages
Proerythroblast divides
Basophilic erythroblast divides
Polychromatophilic erythroblast divides
Orthochromic erthyroblast
Reticulocyte
Erythrocyte
Name these
Proerythroblast: large
Basophilic erythroblast: smaller, very basophilic cytoplasm
Polychromatophilic erythroblasts basophilic & acidophilic cytoplasmic regions
Orthochromatophilic erythroblast: cytoplasm similar to that of a mature RBC
Reticulocyte: lost their nuclei, but not he polyribsoomes to make globin
Control of erythropoiesis (wk long process)
Erythropoietin (EPO): glycoprotein released from kidneys in response to hypoxia
Dietary iron, vitamin B12, and folic acid are also crucical
What’s the first step of granulopoiesis that doesn’t divide?
metamyelocyte.
Granulopoiesis: formation & differentiation of granulocytes
At what stage of granulopoiesis do you start seeing azurophilic granules? Specific granules?
Azurophilic granules - promyelocyte
Specific granules - myelocyte
What is MB? 1-5?
mb- myeloblast (no granules)
1- promyelocyte (blue azurophilic granules)
2- myelocytes (some azurophilic, some specific)
3 & EM - late myelocyte (more specific)
4 & EMm- metamyelocyte (specific granules)
5- band cells (band nucleus)
6-nearly mature segmented neutrophils
Control of granulopoiesis
Colony stimulating factors (CSF): substances relased by macrophage/monocyte community; release stimulated by increased cell migration into tissues, such as in an infection
Neutrophils pass through 4 compartments:
- Granulopoietic: in bone marrow w/developing progenitor cells
- Storage: in red marrow; buffer system that releases large #s of mature neutrophils into blood as needed
- Circulating: blood
- Marginating: cells accumulate temporarily at the surface of the endothelium in venules & small veins
The ___ and __ compartments of granulopoiesis are ~equal size and there is a constant interchange of cells between them.
Circulating & marginating
Process of thrombopoiesis: platelet formation
- Megakaryoblast (Mb): has big nucleus (4n) close to sinuses
-
Promegakaryocyte: has 8n nucleus
- Develops platelet demarcation channels
-
Megakaryocyte (M): giant cell w 32n-64n nucleus
- Very distinct platelet demarcation channel
- Massive protrustion of the cell penetrates a sinus and fragments into platelets
- Thrombocyte (platelet): final end product that circulates in blood; responsible for primary hemostasis (clot formation)
How can you tell that the middle picture is a megakaryocyte and not a megakaryoblast?
It’s less intensely basophilic.
S= sinusoids
Control of thrombopoiesis
Thrombopoietin: serum glycoprotein from liver that simulates megakaryotcytes and platelet production
Autoregulated by platelets, which bind & degrade thrombopoietin
Other red marrow cells
Macrophages/histiocytes: tissue counterparts of monocytes in the blood; perform phagocytosis & iron storage
Structural cells: adipocytes, reticular cells, endothelial cells
Lymphocytes
Mast cells: releases histamine; also has heparin, PAF, etc
G-CSF
Glycoprotein produced in endothelial cells, fibroblasts, and macrophages in different parts of the body to treat neutropenia after cancer chemotherapy or bone marrow transplanatation
If you have a chronic reneal disease, your kidney isn’t making EPO, so you can administer it then monitor the effectiveness by an increase in ___ in circulating blood
Reticulocytes
GM-CSF
Glycoprotein produced by endothelial cells, T cells, fibroblasts, and monocytes that stimulates the formation of neutrophils, eosinophils, basophils, monocytes, and dendritic cells.
Not as effective as G-CSF for neutropenia
Deficiency in vitamin B12 and folic acid causes
megaloblastic anemia: development of large megaloblasts that develop into large RBCs (macrocytes)
Microcytic anemias (small RBCs) are due to a decrease in hemoglobin production caused by:
Lack of hemoglobin product (e.g. thalassemia)
Limited iron availability and suppression of EPO production in inflammation
Lack of iron delivery to the heme group (most common)
Defects in the synthesis of the heme group (sideroblastic anemias, characterized by ringed sideroblasts)
All blood cell types arise from common or pluripotent stem cells, then they can become lymphoid cells that go to the ___ or myeloid cells that develop in the ____.
Lymphoid cells - lymphocytes- leave the marrow to go to the thymus, lymph nodes, spleen, and other lymphoid tissue
Myeloid cells - granulocytes, monocytes, RBCs, megakaryotcytes - develop in bone marrow
