Erythrocyte Production and Destruction Flashcards
What is the major cytoplasmic component of RBCs
and what is it’s function ?
- Hemoglobin
- helps erythrocytes carry oxygen (via binding O2) to tissues
What is the fundamental definition of
anemia ?
- diminished oxygen carrying capacity of the blood
What is another name for polychromatophilic erythrocytes ?
- these are reticulocytes
- when viewed using supravital stains
What is the difference between an erythroblast and erythrocyte?
- erythroblasts are confined to the bone marrow
How long does it take for an erythroid to mature
and enter circulation ?
- 18-21 days
- there are usually 3-5 cell divisions of the pronormoblast to maturation
- from one pronormoblasts 8-32 mature RBCs result
What does cytoplasmic basophilia correlate with in the RBC ?
- amount of ribosomal RNA present
- more basophilic = more RNA
- eosinophilia
- correlates with the amount of hemoglobin in the cytoplasm
What is the last stage of erythroid development
that the cell may undergo mitosis ?
- polychromatophilic normoblast
- also the first stage where the pink color associated with hemoglobin is seen
Which stage of erythrocyte maturation is the nucleus
condensed in the RBC ?
- orthochromatic normoblast
- nucleus is almost pyknotic
- not capable of division
At which normoblast stage is hemoglobin
synthesis first detected?
- basophilic normoblast
- pronormoblast starts gathering all proteins necessary for hemoglobin synthesis
How long does a reticulocyte remain so, before
maturing to a mature RBC ?
- 3 days
- 2 days in the bone marrow
- 1 day in the peripheral blood
What is the normal amount an RBC
remains in the peripheral blood?
- 120 days
- old RBCs are removed by the spleen
RBC morphology
review pgs. 66-70
In a mature erythrocyte
what is the amount of central pallor usually seen ?
What is the difference between the erythron
and RBC mass ?
- Erythron:
- the name given to the entire collection of erythrocytes within the body at all stages
- includes those even within the spleen pending removal
- RBC Mass:
- only the cells in circulation
What is the body’s main system for sensing low oxygen ?
- peritubular fibroblasts of the kidney
- the kidney then produces Erythropoietin
- major stimulatory cytokine for RBC production
- under normal circumstances the amount of EPO production varies very little
- normal amount replaces approximately the 1% of RBCs that are destroyed every day
What is erythropoietin ?
- EPO is a true hormone
- produced in the kidney and acts in the bone marrow
- it is a growth factor/cytokine
When EPO binds to its receptor on immature
RBCs what does it produce?
- leads to increased cell division and maturation
- increased intestinal iron absorption and hemoglobin synthesis
- increased number of RBCs entering the circulation
This physiological response is caused by hypoxia-inducible factors (HIFs)
- these result in gene expression changes leading to erythropoiesis
Ultimately, what is the response of
increased EPO production ?
- allows early release of reticulocytes from the bone marrow
- prevents apoptotic death
- reduces the time needed for cells to mature in the bone marrow
EPO can increase up to 1000 fold if necessary
Why does a fetus/newborn have increased
concentrations of hemoglobin and RBCs ?
- in utero there is a physiologic hypoxia
- HgF is an adaptation to this
- has a higher affinity for oxygen and less readily releases oxygen to the tissues
- as compared to adult HgA
- to compensate for the hypoxia created by HgF
- more RBCs are produced
How is erythropoietin measured ?
- performed on plasma or other body fluids (urine)
- typical normal levels:
- 10-30 U/L sufficient for steady state
- measured by chemiluminiscence
Review bone marrow microenvironment
p. 73-74
How do RBCs produce energy?
- they lack mitochondria
- produce ATP via glycolysis
- the loss of these glycolytic enzymes is part of the process of cellular aging or senescence
- when this occur the RBCs are destroyed by macrophages
