Bone Marrow and Hemopoiesis

Question 1

vascular sinusoids

Answer 1

• “capillaries” of bones.. located between arterioles and venules
• lined by endothelium with basal lamina

Question 2

reticular cell in bone marrow

Answer 2

The precursor for lymphocyte and monocyte formation
-phagocytic cells that line the sinusoid
-cell on outer “adventitia”
extend sheet like processes and reticular fibers into hemopoietic compartments to help organize cells
-newly formed blood cells displace the reticular cells and basal lamina and pass into the sinusoid lumen

Question 3

hemopoietic compartment of red marrow

Answer 3

lie between sinusoids or between the bone and sinusoids

-contain developing blood cells, mature blood cells, megakaryocytes, macrophages, mast cells and adipocytes

Question 4

yellow marrow

Answer 4

adipocytes replace the hemopoietic tissue (predominates in adults but can revert to hemopoiesis if necessary)

Question 5

Hemopoiesis

Answer 5

-formation of RBC, WBC, and platelets (thrombopoiesis)

Question 6

what are all formed elements of blood derived from

Answer 6

• pluripotent stem cell with CD34 surface marker. which gives rise to either multipotential LYMPHOID stem cell (CFU-L) or multipotential MYELOID stem cell (CFU-GEMM)

Question 7

myeloid lineage

Answer 7

erythroid (CFU-E), neutrophil/monocyte (CFU-GM), eosinophil (CFU-Eo), basophil (CFU-Ba) and megakaryocyte (CFU-Meg)

Question 8

Lymphoid lineage

Answer 8

DISTINCT CFU for T and B cells

Question 9

erythropoiesis (general trends)

Answer 9

• regulated by erythropoietin (released from kidney) in response to low oxygen concentration in blood
  1. cells go from a large precurser to small RBC
  2. cytoplasm goes from basophilic to eosinophlic
  3. chromatin becomes progressively denser until the pyknotic nucleus is finally extruded

Question 10

phases of erythropoiesis

Answer 10

1. pronormoblast: basophlic nucleus/cytoplasm
2. basophilic normoblast: more basophilic nucleus/cytoplasm
3. polychromatophilic normoblast: checkerboard nucleus, less basophilic cytoplasm. LAST STAGE FOR MITOSIS
4. orthochromatophilic normoblast: pyknotic (super dense) nucleus. STAGE WHEN NUCLEUS IS GOING TO GET EXTRUDED, more eosinophilic cytoplasm
5. Reticulocyte: immature RBC (has eER and ribosomes, but not nucleus) STAINED WITH AZURE II

Question 11

Granulopoeises controlled by

Answer 11

1. colony stimulating factors (CSFs) secreted by T-cells + others
2. interleukin IL-3 secreted by T-cells

Question 12

stages of granulopoeisis (PMN production?)

Answer 12

even though the granulocytes are derived from different colonies, they still follow similar stages

1. myeloblast: lots of nucleoli, basophilic cytoplasm (less than pronormoblast), no granules present
2. promyelocyte: elliptical nucleus, nonspecific granules present, more cytoplasm
3. Myelocyte: chromatin begins to condense, nucleus flattens on one side, specific granule production LAST STAGE OF MITOTIC ACTIVITY
4. Metamyelocytes: chromatin continues to condense, nucleus is bean shaped, more specific granules
5. Band form: elongated nucleus, folded but unsegmented
6. Segmented neurtophil = final product

Question 13

Thrombopoiesis

Answer 13

regulated by thrombopoietin generated by kidney and liver, GM-CSF, and interleukins

1. megakaryoblast
2. megakaryocyte

Question 14

Granulopoiesis general trends

Answer 14

1. large to small cell
2. round nucleus to lobated
3. decreased cytoplasmic basophilia
4. production of azurophils (nonspecific granules) comes before specific granule production

Question 15

megakaryoblast

Answer 15

about 3x an RBC

• nonlobed nucleus, basophilic cytoplasm
• cell undergoes endomitosis

Question 16

endomitosis

Answer 16

chromosomes are doubled but there is no karyokinesis or cytokinesis
-each replication causes nuclear location and increased size of the cell

Question 17

megakaryocyte

Answer 17

multilobed/infolded nucleus, granular cytoplasm (formation of platelet fields and release platelets directly into sinusoid lumen)

Question 18

thrombopoeisis general

Answer 18

small megakaryocyte (initial lobation of nucleus).. cytoplasm is becoming less prominent. with progression, nucleus is lost. 
platelets = broken bits of material from a megakaryocyte