Chapter 5 Erythrocyte Production and Destruction

Question 1

has one true function: to carry oxygen from the lung to the tissues, where the oxygen is released. This is accomplished by the attachment of the oxygen to hemoglobin, the major cytoplasmic component of mature RBCs.

Answer 1

erythrocyte

Question 2

unique among animal cells in that in its mature, functional state, it does not have a nucleus

Answer 2

mammalian erythrocyte

Question 3

nucleated RBC precursors, normally restricted to the bone marrow, also may be called normoblasts

Answer 3

erythroblasts

Question 4

developing nucleated RBC precursors (i.e., blasts) with normal appearance

Answer 4

normoblasts

Question 5

morphologically identifiable erythrocyte precursors develop from two progenitors, burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E), both committed to the erythroid cell line.

Answer 5

Erythroid Progenitors

Question 6

These erythroid progenitors are named for their ability to form colonies on semisolid media in culture experiments that enable the study of their characteristics and development.

Answer 6

burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E)

Question 7

The earliest committed progenitor, gives rise to large colonies because they are capable of multisubunit colonies (called bursts)

Answer 7

BFU-E

Question 8

gives rise to smaller colonies

Answer 8

CFU-E

Question 9

it takes about 1 week for the BFU-E to mature to the CFU-E and another week for the CFU-E to become a pronormoblast

Answer 9

first morphologically identifiable RBC precursor

Question 10

for the precursors to become mature enough to enter the circulation

Answer 10

it takes approximately another 6 to 7 days

Question 11

required to produce a mature RBC from the BFU-E

Answer 11

approximately 18 to 21 days

Question 12

similar to the proliferation of other cell lines, is a process encompassing replication (i.e., division)to increase cell numbers and development from immature to mature cell stages

Answer 12

Normoblastic proliferation

Question 13

The earliest morphologically recognizable erythrocyte precursor

Answer 13

pronormoblast

Question 14

derived via the BFU-E and CFU-E from pluripotent hematopoietic stem cells

Answer 14

pronormoblast

Question 15

The pronormoblast is able to divide, with each daughter cell maturing to the next stage of development

Answer 15

basophilic normoblast

Question 16

Each of these cells can divide, with each of its daughter cells maturing to the next stage. Each of these cells also can divide and mature

Answer 16

polychromatic normoblast

Question 17

In the erythrocyte cell line, there are typically three and occasionally as many as five divisions with subsequent nuclear and cytoplasmic maturation of
the daughter cells; from a single pronormoblast, therefore

Answer 17

8 to 32 mature RBCs usually result

Question 18

Morphologic identification of blood cells depends on a well-stained

Answer 18

peripheral blood film or bone marrow smear

Question 19

In hematology, a modified Romanowsky
stain, is commonly used, such as

Answer 19

Wright or Wright-Giemsa

Question 20

The stage of maturation of any blood cell is determined by careful examination of the

Answer 20

nucleus and the cytoplasm

Question 21

The most important features in the identification of RBCs are the

Answer 21

nuclear chromatin pattern (texture, density, homogeneity),
nuclear diameter,
nucleus-to-cytoplasm (N:C) ratio,
presence or absence of nucleoli, and
cytoplasmic color

Question 22

As erythroid precursors mature, several general trends affect their appearance, graphically represents these trends.

Answer 22

1. Overall diameter of the cell decreases.
2. Diameter of the nucleus decreases, the N:C ratio also decreases
3. Nuclear chromatin pattern becomes coarser, clumped, and condensed.
4. Nucleoli disappear.
5. Cytoplasm changes from blue to gray-blue to salmon pink.

Question 23

The nuclear chromatin of erythroid precursors
is inherently coarser than that of myeloid precursors. It becomes even coarser and more clumped as the cell matures, developing a

Answer 23

raspberry-like appearance

Question 24

Ultimately the nucleus becomes quite condensed,
with no parachromatin evident at all, and the nucleus is said to be

Answer 24

pyknotic

Question 25

morphologic feature used to identify and stage red blood cell and white blood cell precursors. The ratio is a visual estimate of the area of the cell occupied by the nucleus compared with that of the cytoplasm

Answer 25

nucleus-to-cytoplasm (N:C) ratio

Question 26

In the red blood cell line, the proportion of nucleus shrinks as the cell matures and the cytoplasm increases proportionately, although the overall cell diameter grows smaller

Answer 26

In short, the N:C ratio decreases.

Question 27

nucleoli disappear, which precedes the ultimate cessation of protein synthesis

Answer 27

erythroid precursors mature

Question 28

due to acidic components that attract basic stains, such as methylene blue

Answer 28

Blueness or basophilia

Question 29

due to accumulation of more basic components that attract acid stains, such as eosin

Answer 29

Pinkness, called eosinophilia or acidophilia

Question 30

the cell starts out being active in protein production on the ribosomes that make the

Answer 30

cytoplasm basophilic

Question 31

gradual process, however, with changes occurring in a generally predictable sequence but with some variation for each individual cell

Answer 31

Cell maturation

Question 32

Rubriblast

Answer 32

Pronormoblast

Question 33

nucleus takes up much of the cell

Answer 33

(N:C ratio of 8:1)

Question 34

round to oval, containing one or two nucleoli. The purple red chromatin is open and contains few, if any, fine clumps

Answer 34

Pronormoblast (Rubriblast): Nucleus

Question 35

dark blue because of the concentration of ribosomes and RNA

Answer 35

Pronormoblast (Rubriblast): Cytoplasm

Question 36

may show small tufts of irregular cytoplasm along the periphery of the membrane

Answer 36

Pronormoblast (Rubriblast): Pronormoblast

Question 37

The pronormoblast undergoes mitosis and gives rise to two daughter pronormoblasts

Answer 37

Pronormoblast (Rubriblast): Division

Question 38

The pronormoblast is present only in the bone marrow in healthy states.

Answer 38

Pronormoblast (Rubriblast): Location

Question 39

The pronormoblast begins to accumulate the components necessary for hemoglobin production. The proteins and enzymes necessary for iron uptake and protoporphyrin synthesis are produced. Globin production begins.

Answer 39

Pronormoblast (Rubriblast): Cellular activity

Question 40

This stage lasts slightly more than 24 hours.

Answer 40

Pronormoblast (Rubriblast): Length of time in this stage

Question 41

Prorubricyte

Answer 41

Basophilic Normoblast

Question 42

Basophilic Normoblast (Prorubricyte) Nucleus The chromatin begins to condense, revealing clumps along the periphery of the nuclear membrane and a few in the interior. The parachromatin areas become larger and sharper. The chromatin stains deep purple-red.

Answer 42

N:C ratio decreases to about 6:1

Question 43

When stained, may be a deeper, richer blue than in the pronormoblast, hence the name basophilic for this stage.

Answer 43

Basophilic Normoblast (Prorubricyte): Cytoplasm

Question 44

The basophilic normoblast undergoes mitosis, giving rise to two daughter cells. More than one division is possible before the daughter cells mature into polychromatic normoblasts.

Answer 44

Basophilic Normoblast (Prorubricyte): Division

Question 45

The basophilic normoblast is present only in the bone marrow in healthy states.

Answer 45

Basophilic Normoblast (Prorubricyte): Location

Question 46

Detectable hemoglobin synthesis occurs, but the many cytoplasmic organelles, including ribosomes and a substantial amount of messenger ribonucleic acid (mRNA; chiefly for hemoglobin production), completely mask the minute amount of hemoglobin pigmentation.

Answer 46

Basophilic Normoblast (Prorubricyte): Cellular activity

Question 47

This stage lasts slightly more than 24 hours.

Answer 47

Basophilic Normoblast (Prorubricyte): Length of time in this stage

Question 48

Polychromatic Normoblast

Answer 48

Polychromatophilic Rubricyte

Question 49

Polychromatic Normoblasts (Rubricytes): Nucleus The condensation of chromatin reduces the diameter of the nucleus considerably. Notably, no nucleoli are present.

Answer 49

N:C ratio decreases from 4:1 to about 1:1 by the end of the stage

Question 50

This is the first stage in which the pink color associated with stained hemoglobin can be seen

Answer 50

Polychromatic Normoblasts (Rubricytes): Cytoplasm

Question 51

Polychromatic Normoblasts (Rubricytes): Cytoplasm The stained color reflects the accumulation of hemoglobin pigmentation over time and concurrent decreasing amounts of RNA. The color produced is a mixture of pink and blue, resulting in a

Answer 51

murky gray-blue

Question 52

Polychromatic Normoblasts (Rubricytes): Cytoplasm The stage’s name refers to this combination of multiple colors, because polychromatophilic means

Answer 52

“many color loving.”

Question 53

This is the last stage in which the cell is capable of undergoing mitosis, although likely only early in the stage. Producing daughter cells that mature and develop into orthochromic normoblasts.

Answer 53

Polychromatic Normoblasts (Rubricytes): Division

Question 54

The polychromatic normoblast is present only in the bone marrow in healthy states.

Answer 54

Polychromatic Normoblasts (Rubricytes): Location

Question 55

Hemoglobin synthesis increases, and the accumulation begins to be visible as a pinkish color in the cytoplasm. Cellular RNA and organelles are still present, particularly ribosomes. The progressive condensation of the nucleus and disappearance of nucleoli are evidence of progressive decline in transcription of deoxyribonucleic acid (DNA).

Answer 55

Polychromatic Normoblasts (Rubricytes): Cellular activity

Question 56

This stage lasts approximately 30 hours.

Answer 56

Polychromatic Normoblasts (Rubricytes): Length of time in this stage

Question 57

Metarubricyte

Answer 57

Orthochromic Normoblast

Question 58

Orthochromic Normoblast (Metarubricyte): Nucleus The nucleus is completely condensed (i.e., pyknotic) or nearly so. As a result, the

Answer 58

N:C ratio is low or approximately 1:2

Question 59

The increase in the salmon pink color of the cytoplasm reflects nearly complete hemoglobin production.

Answer 59

Orthochromic Normoblast (Metarubricyte): Cytoplasm

Question 60

The orthochromic normoblast is not capable of division because of the condensation of the chromatin.

Answer 60

Orthochromic Normoblast (Metarubricyte): Division

Question 61

Hemoglobin production continues on the remaining ribosomes using messenger RNA produced earlier. Late in this stage, the nucleus is ejected from the cell. The nucleus moves to the cell membrane and into a pseudopod-like projection.

Answer 61

Orthochromic Normoblast (Metarubricyte): Cellular activity

Question 62

Orthochromic Normoblast (Metarubricyte): Cellular activity As part of the maturation process, a protein responsible for holding organelles in proper location in the cytoplasm

Answer 62

loss of vimentin

Question 63

Orthochromic Normoblast (Metarubricyte): Cellular activity Nonmuscle myosin of the membrane is important in this pinching process.6 The enveloped extruded nucleus, called is then engulfed by bone marrow macrophages.

Answer 63

pyrenocyte

Question 64

Orthochromic Normoblast (Metarubricyte): Cellular activity The macrophages recognize phosphatidylserine on the pyrenocyte surface as an

Answer 64

“eat me” flag

Question 65

Orthochromic Normoblast (Metarubricyte): Cellular activity Often, small fragments of nucleus are left behind if the projection is pinched off before the entire nucleus is enveloped. These fragments are called when seen in peripheral RBCs and are typically removed from the cells by the splenic macrophage pitting process once the cell enters the circulation.

Answer 65

Howell-Jolly bodies

Question 66

This stage lasts approximately 48 hours.

Answer 66

Orthochromic Normoblast (Metarubricyte): Length of time in this stage

Question 67

Polychromatic (Polychromatophilic) Erythrocyte or

Answer 67

Reticulocyte

Question 68

There is no nucleus, when a cell loses its nucleus, regardless of cytoplasmic appearance, it is a polychromatic erythrocyte.

Answer 68

Reticulocyte: Nucleus

Question 69

Hemoglobin yet with a bluish tinge due to some residual ribosomes and RNA. By the end of the polychromatic erythrocyte stage, the cell is the same color as a mature RBC, salmon pink. It remains larger than a mature cell, however. The shape of the cell is not the mature biconcave disc but is irregular in electron micrographs

Answer 69

Reticulocyte: Cytoplasm

Question 70

Lacking a nucleus, the polychromatic erythrocyte cannot divide

Answer 70

Reticulocyte: Division

Question 70

The polychromatic erythrocyte resides in the bone marrow for about 1 to 2 days and then moves into the peripheral blood for about 1 day before reaching maturity

Answer 70

Reticulocyte: Location

Question 71

Reticulocyte: Location The polychromatic erythrocyte is retained in the spleen for pitting of inclusions and membrane polishing by splenic macrophages, which results in the

Answer 71

biconcave discoid mature RBC

Question 72

Reticulocyte: Cellular activity The cytoplasmic protein production machinery is simultaneously being dismantled, digests the ribosomes.

Answer 72

Endoribonuclease

Question 73

Reticulocyte: Cellular activity The residual ribosomes appear as a mesh of small blue strands, a reticulum, or, when more fully digested, merely blue dots. When so stained, the polychromatic erythrocyte is called However, the name reticulocyte is often used to refer to the stage immediately preceding the mature erythrocyte even when stained with Wright stain and without demonstrating the reticulum.

Answer 73

reticulocyte

Question 74

The cell typically remains a polychromatic erythrocyte for about 3 days,4 with the first 2 days spent in the bone marrow and the third spent in the peripheral blood, although possibly sequestered in the spleen.

Answer 74

Reticulocyte: Length of time in this stage

Question 75

Mature Erythrocytes or

Answer 75

Erythrocyte

Question 76

No nucleus is present in mature RBCs.

Answer 76

Erythrocyte: Nucleus

Question 77

Erythrocyte: Cytoplasm The mature circulating erythrocyte is a biconcave disc measuring, with a thickness of about

Answer 77

7 to 8 "m in diameter 1.5 to 2.5 "m.

Question 78

On a Wright-stained blood film, it appears as a salmon-pink stained cell with a central pale area that corresponds to the concavity. The central pallor is about one-third the diameter of the cell.

Answer 78

Erythrocyte: Cytoplasm

Question 79

The erythrocyte cannot divide.

Answer 79

Erythrocyte: Division

Question 80

Mature RBCs remain active in the circulation for approximately 120 days.

Answer 80

Erythrocyte: Location and length of time in this stage.

Question 81

The mature erythrocyte delivers oxygen to tissues, releases it, and returns to the lung to be reoxygenated.

Answer 81

Erythrocyte: Cellular activity

Question 82

Erythrocyte: Cellular activity contains mostly hemoglobin, the oxygen-carrying component. It has a surface area-to-volume ratio and shape that enable optimal gas exchange to occur.

Answer 82

interior of the erythrocyte

Question 83

The cell’s main function of oxygen delivery throughout the body requires a membrane that is

Answer 83

flexible and deformable, that is, able to flex but return to its original shape

Question 84

RBCs must squeeze through small spaces such as the

Answer 84

basement membrane of the bone marrow venous sinus.

Question 85

when a cell enters the red pulp of the spleen, it must squeeze between epithelial cells to move into the

Answer 85

venous outflow

Question 86

crucial for RBCs to enter and subsequently remain in the circulation

Answer 86

Deformability