Chapter 8- Erythrocyte production and Destruction Flashcards
RBCs are formally called
Erythrocytes
The nucleated precursors in the bone marrow are called
erythroblast/ also called normoblasts
The stage of maturation of any blood cell is determined by careful examination of the
nucleus and the cytoplasm
qualities of greatest importance in identification of RBCs are the
nuclear chromatin pattern (texture, density, homogeneity), nuclear diameter, nucleus: cytoplasm ration, presence or absence of nucleoli, and cytoplasmic color
N:C
nuclear: cytoplasm
N:C
used to identify and stage red blood cell and white blood cell precursors.
the identifiable precursors of mature RBCs, in order from youngest to oldest
Pronormoblast, basophilic normoblast, polychromatic normoblast, orthochromic normoblast, polychromatic erythrocyte or reticulocyte.
days for the BFU-E (burst-forming unit-erythroid) to mature to an RBC
18-21 days
the mature erythrocyte has a life span of
120 days
two (2) functionally identifiable progenitors
BFU-E ( burst-forming units-erythroid)
CFU_E ( colony- forming unit- erythroid)
both committed to to the erythroid cell line.
Function of Erythrocyte
to carry oxygen from the lung to the tissues, where the oxygen is released. accomplished by attachment of oxygen to hemoglobin
process encompassing replication, to increase cell numbers and development from immature to mature cell stages
normoblastic proliferation
the earliest morphologically recognizable erythrocyte precursor
pronormoblasts
single pronormoblast
can usually result to 8-32 mature RBCs
commonly used stain in hematology
romanowsky stain, such as Wright-giemsa
Nucleus (pronormoblast)
Takes up much of the cell (N:C ratio of 8:1)
- round to oval
- containing 1-2 nucleoli
Cytoplasm(pronormoblast)
the cytoplasm is dark blue because of the concentration of ribosomes
Division(pronormoblast)
the pronormoblast undergoes mitosis and gives rise to two daughter pronormoblast.
Location (pronormoblast)
pronormoblast is present only in the bone marrow in healthy states.
Cellular activity (pronormoblast)
pronormoblast begins to accumulate the components necessary for hemoglobin production
length of time in this stage
this stage last slightly more than 24 hours
nucleus (Basophilic)
The chromatin begins to condense, revealing
clumps along the periphery of the nuclear membrane and a
few in the interior
Cytoplasm (Basophilic)
When stained, the cytoplasm may be a deeper,
richer blue than in the pronormoblast—hence the name
basophilic for this stage
Division (Basophilic)
The basophilic normoblast undergoes mitosis, giving rise to two daughter cells.
Location (Basophilic)
The basophilic normoblast is present only in
the bone marrow in healthy states
Cellular Activity (Basophilic)
Detectable hemoglobin synthesis occurs, but the many cytoplasmic organelles, including ribosomes
and a substantial amount of messenger ribonucleic acid (RNA;
chiefly for hemoglobin production), completely mask the
minute amount of hemoglobin pigmentation.
Length of time (Basophilic)
This stage lasts slightly
more than 24 hours
nucleus (polychormatic)
The chromatin pattern varies during this stage
of development, showing some openness early in the stage but
becoming condensed by the end.
Cytoplasm (polychormatic)
This is the first stage in which the pink color
associated with stained hemoglobin can be seen
Division (polychormatic)
This is the last stage in which the cell is capable
of undergoing mitosis, although likely only early in the stage.
The polychromatic normoblast goes through mitosis, producing daughter cells that mature and develop into orthochromic
normoblasts
Location (polychormatic)
The polychromatic normoblast is present only in the bone marrow in healthy states
Cellular Activity (polychormatic)
Hemoglobin synthesis increases, and the
accumulation begins to be visible in the color of the cytoplasm.
Length of Time in This Stage. (polychormatic)
This stage lasts approximately 30 hours.
Nucleus ( Orthochromic)
The nucleus is completely condensed (i.e., pyknotic) or nearly so. As a result, the N:C ratio is low or
approximately 1:2
Cytoplasm ( Orthochromic)
The increase in the salmon-pink color of the cytoplasm reflects nearly complete hemoglobin production.
Division ( Orthochromic)
The orthochromic normoblast is not capable of division due to the condensation of the chromatin
Location ( Orthochromic)
The orthochromic normoblast is present only in the bone marrow in healthy states.
Cellular Activity ( Orthochromic)
Hemoglobin production continues on the remaining ribosomes using messenger RNA produced earlier.
Length of Time in This Stage ( Orthochromic)
This stage lasts approximately 48 hours.
Nucleus (Reticulocyte)
when a cell loses its
nucleus, regardless of cytoplasmic appearance, it is a polychromatic erythroc
Cytoplasm (Reticulocyte)
The cytoplasm can be compared with that of
the late orthochromic normoblast in that the predominant
color is that of hemoglobin.
Division (Reticulocyte)
Lacking a nucleus, the polychromatic erythrocyte cannot divide.
Location (Reticulocyte)
The polychromatic erythrocyte resides in the bone marrow for 1 day or longer and then moves into the
peripheral blood for about 1 day before reaching maturity.
Cellular Activity (Reticulocyte)
The polychromatic erythrocyte completes production of hemoglobin from residual messenger
RNA using the remaining ribosomes.
Length of Time in This Stage (Reticulocyte)
The cell typically
remains a polychromatic erythrocyte for about 3 days. 2 in bone marrow and 1 in peripheral blood
Nucleus (erythrocytes)
No nucleus is present in mature RBCs.
Cytoplasm (erythrocytes)
The mature circulating erythrocyte is a biconcave disc measuring 7 to 8 mm in diameter, with a thickness
of about 1.5 to 2.5 mm.
Division (erythrocytes)
The erythrocyte cannot divide
Location and Length of Time in This Stage. (erythrocytes)
Mature
RBCs remain active in the circulation for approximately 120
days.
Cellular Activity (erythrocytes)
The mature erythrocyte delivers oxygen
to tissues, releases it, and returns to the lung to be reoxygenated.
term describing the dynamics of RBC production and destruction
Erythrokinetics
name given to the collection of all stages of erythrocytes throughout the body
Erythron
Hypoxia
low oxygen levels in your tissues
EPO (erythropoietin)
the primary hormone that stimulates the production of erythrocytes, is able to rescue the CFU-E from apoptosis, shorten the
time between mitoses of precursors, release reticulocytes from the
marrow early, and reduce the number of mitoses of precursors
EPO
- thermostable
- nondialyzable
- glycoprotein hormone with molecular weight of 34kD
Apoptosis
is the mechanism by which an appropriate normal production level of cells is controlled.
Which of the following is an erythrocyte progenitor?
a. Pronormoblast
b. Reticulocyte
c. CFU-E
d. Orthochromic normoblas
C
- Which of the following is the most mature normoblast?
a. Orthochromic normoblast
b. Basophilic normoblast
c. Pronormoblast
d. Polychromatic normoblast
A
What erythroid precursor can be described as follows: the
cell is of medium size compared with other normoblasts,
with an N:C ratio of nearly 1:1. The nuclear chromatin is
condensed and chunky throughout the nucleus. No nucleoli are seen. The cytoplasm is a muddy, blue-pink
color.
a. Reticulocyte
b. Pronormoblast
c. Orthochromic normoblast
d. Polychromatic normoblas
D
Which of the following is not related to the effects of erythropoietin?
a. The number of divisions of a normoblast
b. The formation of pores in sinusoidal endothelial cells
for marrow egress
c. The time between mitoses of normoblasts
d. The production of antiapoptotic molecules by erythroid
progenitor
B
Hypoxia stimulates RBC production by:
a. Inducing more pluripotent stem cells into the erythroid
lineage
b. Stimulating EPO production by the kidney
c. Increasing the number of RBC mitoses
d. Stimulating the production of fibronectin by macrophages of the bone marrow
B
In the bone marrow, RBC precursors are located:
a. In the center of the hematopoietic cords
b. Adjacent to megakaryocytes along the adventitial cell
lining
c. Surrounding fat cells in apoptotic islands
d. Surrounding macrophages in erythroid islands
D
Which of the following determines the timing of egress of
RBCs from the bone marrow?
a. Maturing normoblasts slowly lose receptors for adhesive molecules that bind them to stromal cells.
b. Stromal cells decrease production of adhesive molecules over time as RBCs mature.
c. Endothelial cells of the venous sinus form pores at
specified intervals of time, allowing egress of free cells.
d. Periodic apoptosis of pronormoblasts in the marrow
cords occurs.
A
What single feature of normal RBCs is most responsible for
limiting their life span?
a. Loss of mitochondria
b. Increased flexibility of the cell membrane
c. Reduction of hemoglobin iron
d. Loss of the nucleus
D
Intravascular or fragmentation hemolysis is the result of
trauma to RBCs while in the circulation.
a. True
b. False
A
Extravascular hemolysis occurs when:
a. RBCs are mechanically ruptured
b. RBCs extravasate from the blood vessels into the tissues
c. Splenic macrophages ingest senescent cells
d. Erythrocytes are trapped in blood clots outside the
blood vesselS
C
A pronormoblast in its usual location belongs to the RBC
mass of the body, but not to the erythron.
a. True
b. False
B
A cell has an N:C ratio of 4:1. Which of the following statements would describe it?
a. The bulk of the cell is composed of cytoplasm.
b. The bulk of the cell is composed of nucleus.
c. The proportions of cytoplasm and nucleus are roughly
equal.
B
