lecture 4 Flashcards
why are reticulocytes called reticulocytes?
They are called reticulocytes because of a reticular (mesh-like) network of ribosomal RNA
what are the dark intracellular features found inside the reticulocytes?
vacuoles that contain remnants of organelles (ER, golgi, mitochondria) that are released from the cell as it matures
the ribosomal RNA of a reticulocyte is stained with which type of stain?
new methylene blue
what is the normal range of reticulocyte in men and women?
men: 0.5-1.5%
women: 0.5-2.5%
low reticulocyte count is seen in people with:
cirrhosis, folic acid deficiency, and bone marrow failure
high reticulocyte count is seen in people with:
bone marrow is responding to the need for increased RBC production (person who has recently donated blood or responding to treatment for anemia)
what is the procedure for reticulocyte count?
- put a drop of a supravital stain BCB (Brilliant Cresyl blue) on a slide and spread it
- slide will become blue
- air dry for 1 min
- put a drop of a supravital stain BCB (Brilliant Cresyl blue) on a slide and spread it
- Using a capillary tube, place a drop of anticoagulated blood on each side of the slide
- cover it with a cover slip (push a little on the cover slip + air dry for 10 mins)
- Using a capillary tube, place a drop of anticoagulated blood on each side of the slide
- using low-power objective (10x), find an area in the thin portion of the smear in which the red cells are evenly distributed and are not touching each other
- Carefully change to oil immersion (100x) and further locate an area in which there are approx 200 RBC per oil immersion field
- Select 5 fields.
- same is done for the second side of the slide
- using low-power objective (10x), find an area in the thin portion of the smear in which the red cells are evenly distributed and are not touching each other
- Count reticulocytes in 5 fields.
- Record the number of retics seen
- calculate the % of reticulocytes using formula
- Count reticulocytes in 5 fields.
what is the formula to calculate the % reticulocytes?
% Reticulocytes= number of reticulocytes counted in 1000 red cells /10
what are the stages of erythropoesis?
- myeloid stem cell
- proerythroblast = pronormoblast
- basophilic (early) erythroblast
- polychromatic (intermediate) erythroblast
- orthochromatic (late) erythroblast
- reticulocyte (polychromatic reticulocyte)
- erythrocyte
what are the major changes during the process of development of the RBC(s)?
- size of cell becomes smaller
- size of nucleus becomes smaller
- chromatin becomes denser
- basophilia gradually decreases until in the mature RBC there is no RNA.
proerythroblast key points
- first recognizable cell
- large cell
- large nucleus
- contains very fine-chromatin
- few nucleoli (1-4)
- cytoplasm is abundant + intensely basophilic (due to presence of a large amount of RNA)
- appears as a band around the nucleus
- can either undergo mitosis to make another proeythroblast or can mature to give the Basophilic/early erythroblast
Early erythroblast key points
- becomes smaller in size
- nucleus becomes smaller
- chromatin pattern becomes coarser (condensed)
- no more nucleoli
- cytoplasm is still intensely basophilic but less than
proerythroblast - can also divide to give another early erythroblast
or can mature to a polychromatophilic (intermediate) erythroblast.
Intermediate erythroblast key points
- cell becomes smaller
- nucleus becomes smaller
- chromatin more condensed
- cytoplasm is less basophilic and appears grayish to pinkish
- Hb starts to add up (production of Hb)
- can divide or mature to an orthochromic (late) erythroblast.
Late erythroblast key points
- cell smaller
- smaller nucleus
- nucleus is completely condensed (pyknotic nucleus)
- cytoplasm becomes more abundant + more pinkish
- no more able of further mitosis (because the nucleus is so condensed that the DNA material cannot replicate)
- nucleus is extruded, taken by phagocytes of the B.M
- cell becomes anucleated
what is the major modification in a basophilic erythroblast?
no more nucleoli
what is the major modification in a polychromatic erythroblast?
- cytoplasm is less basophilic (grayish to pinkish)
- Hb starts to add up (Hb production)
what is the major modification in an orthochromic erythroblast?
- nucleus is completely condensed (pyknotic nucleus)
- no more able of further mitosis
- nucleus is extruded
- cell becomes anucleated.
in what stage is the cell no more able of further mitosis? and why?
- in orthochromic (late) erythroblast
- no more able of further mitosis because the nucleus is so condensed that the DNA material cannot replicate
what is the name of the nucleus that is completely condensed?
pyknotic nucleus
reticulocyte key points
- nucleus is extruded
- contains some residual organelles (ribosomes,
mitochondria) - organelles can be stained with a supravital stain –> reticular appearance
- stays in BM for 48 hrs
- leaves BM to the circulation for 18-24 hrs (1 day)
- passes by the spleen (where organelles are removed)
- cell becomes a mature RBC
- 0.2-2% of all RBC(s) in circulation are reticulocytes
where do reticulocytes become mature RBCs?
in the spleen (where
residual organelles are removed)
how long do reticulocytes stay in BM?
for 48 hrs
how long do reticulocytes circulate?
18-24hrs (1 day)
how is erythropoiesis initiated?
- initiated by a hormone (erythropoietin)
- erythropoietin is produced by the kidney+ found in plasma
- stimulus to erythropoietin secretion is O2 tension in blood
- low O2 tension (hypoxia) –> stimulation of kidneys –> erythropoietin –> RBC production
how RBC production is stimulated by erythropoietin?
- activating self renewal of stem cells –> stem cells increase in number
- activating stem cells to differentiate into
proeythroblasts
–> increased number of RBC(s) are produced - increasing the rate of mitosis
- decreasing maturation time of RBC(s) in B.M.
- increasing the release of RBC(s) from the BM to PB
including immature RBC(s).
when the body needs more red cells, following blood loss or hemorrhage, more of the mature cells pass out to the circulation (T/F)
false, immature cells
when do reticulocyte count rises?
When the body needs more red cells, following blood loss or hemorrhage, then more of the immature red cells pass out to the circulation in order to compensate for this loss
a high reticulocyte count reflects ______
reflects an active BM (BM is compensating for lost red cells)
if reticulocytes are not found in the PB, it means that____
BM is not functioning normally and we don’t have
normal RBC production in the B.M.
depressed reticulocyte counts may denote a very serious marrow disease, for example:
- marrow aplasia
- replacement of erythroid precursors by leukemic cells
what happens to Hb and RBC count if someone lives in the mountains?
usually has a high Hb and RBC count in order to compensate for the decreased O2 tension
what does it mean if we find a high increase in the reticulocyte count /polychromasis, with some erythroblasts present?
this person is destroying RBC(s) somewhere
what happens if someone is destroying his own RBCs?
- decreased O2 tension
- increased production of erythropoietin
- stimulation of BM to produce more RBC(s).
- If hemolysis is severe, erythroblasts may go in
to the circulation along with reticulocytes - high increase in the reticulocyte count /polychromasis, with some erythroblasts present
