CH 33 STRUCTURE AND COMPOSITION OF THE ERYTHROCYTE

Question 1

the progenitors, precursors, and adult red cells make up an organ termed the______, which arises from pluripotential hematopoietic stem cells.

Answer 1

erythron

Question 2

the first morphologically recognizable erythroid precursor cell in the marrow

Answer 2

proerythroblast

Question 3

Following commitment to the erythroid lineage, unipotential progenitors mature into the erythroid progenitors, the ________and, subsequently, the ______, which then undergoes further maturation to generate anucleate polychromatophilic macrocytes

Answer 3

burst-forming unit–erythroid (BFU-E)

colony-forming unit–erythroid (CFU-E)

Question 4

The hallmark of this primitive erythron is the______

Answer 4

release of nucleated erythroid precursors containing embryonic hemoglobin

Question 5

The definitive stage of maturation makes its appearance around week ____ of embryogenesis when mul- tipotential stem cells develop and seed the liver, which maintains the erythron for most of fetal life.

Answer 5

5

Question 6

The earliest identifiable progenitor committed to the erythroid lineage

Answer 6

BFU-E

Question 7

As erythroid maturation progresses, a later progenitor, the ____, derived from the BFU-E, can be defined in vitro.

Answer 7

CFU-E

Question 8

True/False

The CFU-E is independent on erythropoietin for its development and can undergo only a few cell divisions.

Answer 8

FALSE

The CFU-E is dependent on erythropoietin for its development and can undergo only a few cell divisions.

Question 9

Adhesion between erythroid cells and macrophages occurs at the _____ stage of maturation.

Answer 9

CFU-E

Question 10

The anatomical unit of erythropoiesis in the normal adult is the _______.

• consists of a centrally located macrophage surrounded by maturing terminally differentiating erythroid cells

Answer 10

erythroblastic island or islet

Question 11

True/False

erythroblastic islands near sinusoids are composed of more mature erythroblasts, whereas islands more distant from the sinusoids are composed of proerythroblasts

Answer 11

True

erythroblastic islands near sinusoids are composed of more mature erythroblasts, whereas islands more distant from the sinusoids are composed of proerythroblasts

Question 12

TRUE/FALSE

the macrophage of the erythroblastic island appears to play a stimulatory role in erythropoiesis independent of erythropoietin.

Answer 12

TRUE

the macrophage of the erythroblastic island appears to play a stimulatory role in erythropoiesis independent of erythropoietin.

Question 13

They are the largest red cell precursor.

The nucleus occupies approximately 80% of the cell area with a fine nuclear chromatin pattern, distinct nucleoli, deeply basophilic cytoplasm, and often a clear area at the site of the Golgi apparatus.

Answer 13

Proerythroblast

Question 14

The cell is smaller than the proerythroblast.

The nucleus occupies three-fourths of the cell area, the nuclear chromatin is slightly more condensed, and cytoplasm is basophilic.

Answer 14

Basophilic erythroblas

Question 15

The cell is smaller on average than its precursors.
The nuclear chromatin is more condensed, with a checkerboard pattern that develops.
Nucleoli are usually not apparent.
The cytoplasm is gray, reflecting the staining modulation induced by hemoglobin synthesis, which adds cytoplasmic content that takes an eosinophilic stain, admixed with the residual basophilia of the fading protein synthetic apparatus.

Answer 15

Polychromatophilic erythroblasts

Question 16

Stage where erythroblasts lose their mitotic potential

Answer 16

Polychromatophilic erythroblasts

Question 17

This cell is the smallest of the erythroblastic series. increased condensation of nuclear chromatin, with homogeneous cytoplasmic coloration approaching that of a red cell.

Answer 17

Orthochromic normoblast.

Question 18

Chronologic order of RBC maturation

Answer 18

Proerythroblasts->Basophilic erythroblast
->Polychromatophilic erythroblast -> Orthochromic erythroblast.

(Remember P - BPO)

Question 19

T/F

All normal erythroblasts are sideroblasts.

Answer 19

True

All normal erythroblasts are sideroblasts in that they contain iron in structures called siderosomes, as evident by transmission electron microscopy. These structures are essential for the transfer of iron for heme (hemoglobin) synthesis.

Question 20

under the usual conditions of Prussian blue staining for iron, a minority of normal erythroblasts (approximately _____ %) can be identified as containing siderosomes, and those that can be so identified have very few (_____) small Prussian blue–positive granules.

Answer 20

15–20%

1–4

Question 21

A heterogeneous group of erythrocyte disorders is accompanied by ineffective erythropoiesis, abnormal erythroblast morphology, and hyperferremia.

Answer 21

Pathologic Sideroblasts

Question 22

Pathologic sideroblasts are of two types:

Answer 22

The first is an erythroblast that has an increase in number and size of Prussian blue–stained siderotic granules throughout the cytoplasm.

The second is the erythroblast which shows iron-containing granules that are arranged in an arc or a complete ring around the nucleus.

Question 23

Expulsion of the enucleation in vitro is not an instantaneous phenomenon; it requires a period of ____ minutes.

Answer 23

6 to 8

Question 24

T/F

After nuclear extrusion, the reticulocyte retains mitochondria, small numbers of ribosomes, the centriole, endoplasmic reticulum and remnants of the Golgi apparatus.

Answer 24

FALSE

After nuclear extrusion, the reticulocyte retains mitochondria, small numbers of ribosomes, the centriole, and remnants of the Golgi appa- ratus.

It contains no endoplasmic reticulum.

Question 25

“Stress” reticulocytes are released into the circulation during an intense erythropoietin response to acute anemia or experimentally in response to large doses of exogenously administered erythropoietin.34 These cells may be twice the normal volume, with a corresponding increase in mean cell hemoglobin (MCH) content.

Answer 25

Macroreticulocytes

Question 26

are small nuclear remnants/DNA

The crisp circular border, dark blue color, and peripheral location are characteristic.

characteristically present in persons who have undergone splenectomy and in patients with megaloblastic anemia, and hyposplenic states

Answer 26

Howell-Jolly Bodies

Question 27

• sometimes used as a surrogate test for splenic function.
• membrane “pits” or craters. The vesicles or indentations characterizing these cells represent autophagic vacuoles adjacent to the cell membrane.

Answer 27

Pocked (or Pitted) Red Cells

Question 28

The ringlike or figure-of-eight structures sometimes seen in megaloblastic anemia within reticulocytes and in an occasional, heavily stippled, late-intermediate megaloblast.

Their composition is nuclear but some investigators have suggested that they originate from spindle material that was mishandled during abnormal mitosis.

Answer 28

Cabot rings

Question 29

consists of granulations of variable size and num- ber that stain deep blue with Wright stain

represents aggregated ribosomes

In conditions such as lead intoxication, pyrimidine 5’-nucleotidase deficiency and thalassemia.

Answer 29

Basophilic Stippling

Question 30

composed of denatured proteins, primarily hemoglobi, that form in red cells as a result of chemical insult; in hereditary defects of the hexose monophosphate shunt ; in the thalassemias; and in unstable hemoglobin syndromes

Answer 30

Heinz Bodies

Question 31

T/F

Heinz bodies are readily seen on Wright- or Giemsa-stained blood films.

Answer 31

False

Heinz bodies are NOT seen on ordinary Wright- or Giemsa-stained blood films.

Readily visible in red cells stained supravitally with brilliant cresyl blue or crystal violet

Question 32

composed of β4 tetramers, indicating that β chains are present in excess as a result of impaired α-chain production.

Exposure to redox dyes such as brilliant cresyl blue, methylene blue, or new methylene blue, results in denaturation and precipitation of abnormal hemoglobin.

Answer 32

Hemoglobin H Inclusions

Question 33

are siderosomes that stain with Wright stain. Electron microscopy of Pappenheimer bodies shows that the iron often is contained within a lysosome, as confirmed by the presence of acid phosphatase.

Answer 33

Pappenheimer bodies

Question 34

T/F

The decrease in RBC size likely results from loss of membrane surface area during the erythrocyte life span by spleen-facilitated vesiculation.

Answer 34

TRUE

The decrease in size likely results from loss of membrane surface area during the erythrocyte life span by spleen-facilitated vesiculation.

Question 35

The resiliency and fluidity of the membrane to deformation is regulated by the ____-based membrane skeleton.

Answer 35

spectrin

Question 36

Usual life span of RBCs

Answer 36

120 days

Question 37

Red cell deformability is influenced by three distinct cellular components:

Answer 37

(1) cell shape or cell geometry
(2) cytoplasmic viscosity
(3) membrane deformability and mechanical stability, which are regulated by multiple membrane properties, which include elastic shear modulus, bending modulus, and yield stress

Question 38

Red cell deformability

determines the ratio of cell surface area to cell volume (SA:V; higher values of SA:V facilitate deformation);

Answer 38

cell shape or cell geometry

(~Shape/Surface Area)

Question 39

Red cell deformability

primarily regulated by the mean corpuscular hemoglobin concentration (MCHC)

is therefore influenced by alterations in cell volume

Answer 39

cytoplasmic viscosity

viscosity increases exponentially at hemoglobin concentrations >37 g/dL, reaching 45 cP at 40 g/dL, 170 cP at 45 g/dL, and 650 cP at 50 g/dL. At these levels, cytoplasmic viscosity may become the primary deter- minant of cellular deformability.

(~Viscosity/Volume)

Question 40

regulated by multiple membrane properties, which include elastic shear modulus, bending modulus, and yield stress

Answer 40

membrane deformability and mechanical stability

(Mechanical stability/Membrane properties+Modulus)

Question 41

represent red cells, with the most decreased SA:V ratio

Answer 41

Spherocytes

Question 42

may be seen in obstructive liver disease, hemoglobinopathies (S and C), thalassemia, iron deficiency, postsplenectomy, and lecithin cholesterol acetyltransferase deficiency.

relative excess of membrane surface area or decreased cell volume leading to increased SA:V ratio

osmotically resistant

Answer 42

Target Cells (Codocytes)

Question 43

fusiform cell in the crescent shape with two pointed extremities is encountered most commonly in deoxygenated blood samples as a result of polymerization of sickle hemoglobin

Answer 43

Sickle Cells (Drepanocytes)

Question 44

(RBC inclusion - Composition)

Wright Stain:
Howell Jolly Body
Basophilic Stippling
Pappenheimer Body
Cabot Rings

Supravital Stain:
Heinz Body
Hgb H

Answer 44

Wright Stain:
Howell Jolly Body - DNA
Basophilic Stippling - RNA/Ribosomes
Pappenheimer Body - Iron
Cabot Rings - Mitotic Spindle

Supravital Stain:
Heinz Body - unstable hemoglobin
Hgb H - B tetramers