Hematopoiesis

Where does hematopoeisis occur in the fetus versus the infant and adult?

fetus: yolk sac then liver then bone marrow

infants and adults: bone marrow

explain yellow versus red marrow components and age

red marrow: highly vascular

yellow marrow: filled with adipocytes

age: as you get older most of your red marrow becomes yellow marrow

What do we expect to see in normal bone marrow?

trilineage: WBCs (myeloid), RBCs (erythroid), and platelets (megakaryocytes)

how do we calculate cellularity changes with age and why do we care?

100 - age and then its ±10% of that number

• ex: age is 50: 100-50= 50% then ±10% so range is 40%-60%

we care because this number can help us identify if the bone marrow is normocellular, hypercellular, or hypocellular

What cell gives rise to all of the progenitor stem cells (CFUs)

pluripotent stem cells

What is extramedullary hematopoiesis and when does it occur?

this is when the bone marrow can’t keep up with the needs of the body so the liver, spleen, and lymph nodes start producing blood cells instead (this is due to something pathological happening)

The colony forming units, CFU-GEMM, do what?

they further differentiate into various blood cell types including granulocytes, erythrocytes, monocytes, and megakaryocytes

the pluripotent stem cell can go down one of two paths, what are they?

lymphoid: eventually create T and B cells

myeloid: eventually create macrophages, neutrophils, eosinophils, basophils, platelets, or RBCs

you see erythropoetin think ____

you see thrombopoetin think _____

erythropoietin: RBCs

thrombopoietin: platelets

What are the stages for differentiating into a neutrophil?

prominent nuclei → large cell with primary granules → secondary granules appear → kidney-bean shaped nucleus → condensed, band-shaped nucleus → condensed multilobed nucleus

myeloblast → promyelocyte → myelocyte → metamyelocyte → band form → neutrophil

What are the two cell types of neutrophils lineage that can/should be seen in peripheral blood?

Band forms and mature neutrophils (you shouldn’t see myeloblasts or myelocytes unless something is wrong)

When in the lineage can we tell what the cell will differentiate into: eosinophils vs basophils vs neutrophils

they all start out as myeloblasts and we don’t know, we have to wait until:

late myelocyte or early metamyelocyte stage

monoblasts differetiate into:

monocytes (in blood) macrophages (in tissue)

At what point in the lineage of a RBC does it lose its nucleus?

between the polychromatic erthyroblast/normoblast and the reticulocyte stage

Why would we see increased reticulocytes in the blood?

these are the immature stage right before they become an erythrocyte (RBC) so the bone marrow is over producing these precursors to compensate for bleeding, anemia, etc.

thrombocytes aka _____ are derived from what?

thrombocytes = platelets

derived from megakaryocytes

stimulated by thrombopoetin

give a brief overview of megakaryoblasts, thrmbropoetin, and platelets (thrombocytes)

megakaryocytes are large cells with nonlobed nucleus that have platelet demarcation channels that make the platelets that bud off from them

stimulated by thrombopoietin

What type of cell should we associate with infection, inflammation, and stress?

increase in WBCs

mostly neutrophils

What cell ine is responsible for bleeding issues? what hormone regelutes their production?

platelets; thrombopoietin

When and why would we see erhtroid hyperplasia?

when there is a low number of RBCs in the peripheral blood, then the bone marrow tries to fix the issue

seen commonly in anemia

Whar cell line is associated with allergies and asthma?

eosinophils