Flashcards in Bone Marrow and Hematopoiesis Deck (61):
Contrary to as in other cell types, in blood precursor cells the nucleolus stains _____.
How does the nucleus appear in an immature cell?
Larger and more pale
What does it mean if a nucleus is pyknotic?
It is very dense with chromatin/made up entirely of heterochromatin. Appears this way shortly before extrusion in maturing blood cells
How does the nucleus mature during blood cell maturation?
Condenses, gets smaller, eventually is extruded (RBCs) or segmented (granulocytes)
How does cytoplasm change in maturing erythrocytes?
Cytoplasm is basophilic in immature erythrocytes and becomes increasingly eosinophilic as hemoglobin accumulates/ribosomes degrade.
The _____ granules stain the same color as the nucleus in the _____ stain.
azurophilic, Wright stain
Azurophilic granules are ______ granules. Describe their size.
Primary. Tend to be smaller and more variable in size.
Eosinophilic granules are _____ granules. Describe them.
Secondary. Tend to be larger and rounder and more uniform than primary granules.
Passage between marrow and stromal tissue is mediated by ______ cells.
Red marrow is composed mostly of ____ cells.
Yellow marrow is composed mostly of _____ cells.
Is the conversion from red to yellow marrow reversible?
Yes, if a need for more blood-forming capacity arises
What is the role of marrow adipocytes?
Controlling osteogenesis and vascular growth through growth factors and other chemokines.
What are marrow cells of mesenchymal origin?
Osteoblast, fibroblast, endothelial, mesenchymal stem cell
Where are osteoblasts found and what do they do?
Found at the margins of marrow space.
Secrete collagen and a variety of glycoproteins to produce new bone matrix.
Maintain hematopoietic microenvironment.
What do fibroblasts do?
Secrete components of the ECM and produce colony stimulating factors that act on progenitor cells.
Usually are the most closely apposed stromal cells to hematopoietic cells.
What does the endothelial cell do?
Form the vascular lining and controls passage of cells between marrow and general circulation, primarily through expression of adhesion molecule (e.g. CD34)
What do mesenchymal stem cells do?
Differentiate into adipocytes, osteoblasts, and other non-hematopoietic stromal cells. Produce cytokines and regulate microenvironment.
What are the stromal cells of hematopoietic origin?
Macrophages, osteoclasts, connective tissue fibers, blood supply
What do macrophages do?
Phagocytose senescent cell and particulate debris.
Secrete cytokines that maintain and encourage the development of surrounding hematopoietic cells.
What cells are the progeny of CFU-GM progenitor cells?
Where does the osteoclast reside and what does it do?
Resides in the margins of the marrow.
What are sinusoids?
Flattened endothelial cells that have little or no basement membrane. Created by capillaries.
By week ___ the fetal circulation system is established.
Hematopoietic precursors are first observed in the ____ and ____ week of gestation.
3rd and 4th
When does blood cell production begin in the marrow?
5th month of gestation
By age 25, red marrow is confined to where?
Proximal quarters of the long bones, the skull, bones, ribs, sternums, scapulae, pelvis, etc.
In adulthood, hematopoietically active bone is confined to what kind of bone?
What daughter cells do pluripotent hematopoietic stem cells (PHSCs) give rise to?
CMP (common myeloid progenitor) and CLP (common lymphoid progenitor)
What are progenitor cells?
Cells capable of self-renewal but are committed to one cell line. Often referred to as colony forming units.
What factors influence differentiation of hematopoietic stem cells?
Colony stimulating factors (CSFs)
What is a precursor cell?
A cell that can only divide into a further differentiated cell and CANNOT renew itself.
What organ monitors/controls the amount of circulating RBCs?
Kidneys. They make the cytokine erythropoietin in response to low levels of RBCs.
What does erythropoietin stimulate?
What do nurse cells do?
Macrophages that phagocytose the nucleus after an RBC expels it.
What will you see in peripheral blood if the need for RBCs is especially high?
A higher number of reticulocytes as the body keeps pumping out the baby RBCs to erase the deficit.
What makes a reticulocyte a reticulocyte?
Fine reticulum of RNA and protein still in the cell from the maturation process.
What is the progression from Myeloblasts to specific granules (n,e, or b)?
Myeloblasts -> Promyleocytes -> myelocytes -> specific granules
What are stab/band cells and what do they indicate if elevated?
Immature neutrophils, in times of great neutrophil need they can be released from marrow more frequently
What is weird about megakaryoblasts?
They undergo endomitosis (chromosome duplication but no division) and are thus polyploid.
What does the CFU-Meg progenitor produce?
Megakaryoblast and Promegakaryocyte
Are B cells immunocompetent by the time they leave the bone marrow?
Are T cells immunocompetent by the time they leave the bone marrow?
No, they must mature in the thymus
What are the 2 major classes of T cells?
CD4 and CD8
What are the stages of monocyte maturation?
CFU-GM -> monoblast -> promonocyte -> monocyte
The reduction of the ability to carry oxygen to tissues, usually due to a reduction of the number of circulating RBCs.
What are the 3 classes of anemia?
1. Too few RBCs
2. Too many RBCs (polycythemia)
3. Inadequate RBC function (e.g. sickle cell)
Abnormal qualities or quantitites of white blood cells (leukocytes).
What are the classifications of leukemia?
Acute or Chronic
Myeloid or Lymphoid
Thus ALL, AML, CLL, CML
What do lymphoid leukemias refer to?
Cells deriving from CLP
What do myeloid leukemias refer to?
Cells deriving from CMP
At what age is red marrow no longer predominant?
What is the stroma?
Supporting tissue (e.g. in bone marrow adipose, reticular cells, connective tissue, blood supply(
What is the parenchyma?
The functional tissue
What are the mesenchymal derived cells?
What are the hematopoietically derived cells?
PHSCS are ____potent
The first precursor cell in each lineage is a "_____"
blast. (e.g. myeloblast)
Are cells weeded out at each step of stem/progenitor/precursor cells?
Yes! Die via apoptosis
At what stage of maturation do granulocytes leave the marrow and enter the bloodstream?
Band cells or sometimes even fully mature