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Guyton And Hall Physiology > Chapter 33 > Flashcards

Chapter 33 Flashcards

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1
Q

What is the average life span of a normal red blood cell in the circulation?

A

120 days

Normal red blood cells survive about 120 days before being removed by the spleen.

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2
Q

Which organ is most responsible for releasing erythropoietin (EPO) in response to hypoxia?

A

Kidney

The kidney’s interstitial fibroblasts are the primary source of erythropoietin.

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3
Q

What is the shape of mature red blood cells?

A

Biconcave discs without nuclei

RBCs lack nuclei and most organelles, maximizing surface area for gas exchange.

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4
Q

What is the primary function of red blood cells?

A

Transport oxygen and carbon dioxide

RBCs carry oxygen from the lungs to tissues and facilitate carbon dioxide transport back.

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5
Q

Hemoglobin is primarily composed of?

A

Four globin chains and four heme groups

Adult hemoglobin consists of two alpha and two beta globin chains, each with a heme group.

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6
Q

Which form of hemoglobin binds oxygen most readily?

A

Oxyhemoglobin

Oxyhemoglobin is hemoglobin that is bound to oxygen.

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7
Q

Iron is absorbed primarily in which part of the gastrointestinal tract?

A

Duodenum

The duodenum is the primary site of iron absorption.

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8
Q

Which cell type eventually becomes a mature RBC in the peripheral blood?

A

Reticulocyte

Reticulocytes are immature RBCs that mature into erythrocytes within about 1-2 days.

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9
Q

Erythropoietin production is stimulated by?

A

Low oxygen levels

Hypoxia in the kidney stimulates erythropoietin secretion.

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10
Q

The most important regulator of RBC production is?

A

Erythropoietin

Erythropoietin is the key hormone regulating RBC production in the bone marrow.

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11
Q

Which nutrient deficiency leads to megaloblastic anemia?

A

Vitamin B12 and folate

Deficiencies in vitamin B12 or folic acid impair DNA synthesis, causing megaloblastic anemia.

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12
Q

What is the role of transferrin in iron metabolism?

A

Transport of iron in the blood

Transferrin binds and transports iron through the bloodstream to tissues.

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13
Q

The majority of iron in the body is found in?

A

Hemoglobin in RBCs

About two-thirds of the body’s iron is in the heme structure of hemoglobin.

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14
Q

A low reticulocyte count in a patient with anemia suggests?

A

Reduced RBC production

A low reticulocyte count indicates inadequate bone marrow response.

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15
Q

Iron deficiency anemia typically presents as?

A

Microcytic, hypochromic anemia

Iron deficiency leads to smaller RBCs that are paler due to reduced hemoglobin content.

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16
Q

Pernicious anemia is caused by a deficiency of?

A

Intrinsic factor leading to B12 malabsorption

Pernicious anemia results from autoimmune gastritis that reduces intrinsic factor.

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17
Q

The normal red blood cell count in men is approximately?

A

5 million/µL

Normal RBC count for men averages around 5.2 million/µL.

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18
Q

Bilirubin is formed from the breakdown of?

A

The heme portion of hemoglobin

Heme is degraded to biliverdin and then bilirubin when RBCs are destroyed.

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19
Q

Polycythemia vera is characterized by?

A

Increased RBC mass due to a myeloproliferative disorder

Polycythemia vera is a bone marrow disorder causing excessive RBC production.

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20
Q

In response to chronic hypoxia, the body compensates by?

A

Increasing RBC production

Chronic hypoxia stimulates the kidney to produce more EPO, leading to increased RBC production.

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21
Q

The key regulator of iron absorption from the gut is?

A

Hepcidin

Hepcidin regulates intestinal iron absorption and release from stores.

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22
Q

Aplastic anemia involves?

A

Failure of the bone marrow to produce RBCs

Aplastic anemia results from inadequate hematopoiesis in the bone marrow.

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23
Q

What does ferritin do?

A

Stores iron, doesn’t regulate absorption directly

Ferritin is a protein that serves as a storage form of iron in the body.

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24
Q

What is aplastic anemia?

A

Failure of the bone marrow to produce RBCs

Aplastic anemia results in insufficient production of all blood cell types, including red blood cells.

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25
Which substance is crucial for DNA synthesis in RBC precursors?
Vitamin B12 ## Footnote Vitamin B12 deficiency can lead to megaloblastic anemia due to impaired RBC maturation.
26
The oxygen-carrying capacity of blood is directly proportional to:
The hemoglobin concentration ## Footnote More hemoglobin means a greater capacity to carry oxygen in the blood.
27
Which condition leads to normocytic, normochromic anemia?
Acute blood loss ## Footnote Acute hemorrhage initially presents as normocytic, normochromic anemia before compensatory changes occur.
28
Hemolytic anemias are characterized by:
Increased RBC destruction ## Footnote Hemolytic anemia involves the premature destruction of RBCs, leading to elevated bilirubin levels.
29
Carbonic anhydrase in RBCs facilitates:
Conversion of CO2 and H2O into H2CO3 ## Footnote This reaction aids in the transport of carbon dioxide in the blood.
30
The normal hematocrit for a healthy adult male is approximately:
45% ## Footnote Normal male hematocrit is around 40-50%, with 45% being a common value.
31
In iron deficiency anemia, serum ferritin levels are typically:
Low ## Footnote Ferritin levels drop in iron deficiency as it reflects body iron stores.
32
Excessive RBC destruction often leads to:
Jaundice (increased bilirubin) ## Footnote Hemolysis increases free bilirubin load in the body, which can cause jaundice.
33
Hemoglobin F (fetal hemoglobin) differs from adult hemoglobin (HbA) because it:
Has a higher affinity for oxygen ## Footnote This higher affinity facilitates oxygen transfer from maternal to fetal blood.
34
The final step in heme synthesis occurs in the:
Mitochondria of RBC precursors ## Footnote Heme synthesis begins in the mitochondria, moves to the cytosol, and ends back in the mitochondria.
35
Iron overload (hemochromatosis) can damage organs due to:
Iron-mediated oxidative stress ## Footnote Excess iron can lead to the formation of free radicals, causing tissue damage.
36
The normal mean corpuscular volume (MCV) for RBCs is approximately:
80-100 fL ## Footnote Normal MCV indicates the average size of RBCs; values outside this range suggest microcytosis or macrocytosis.
37
Chronic renal failure often leads to anemia because:
The kidneys produce inadequate EPO ## Footnote Damaged kidneys do not produce sufficient erythropoietin (EPO), reducing RBC production.
38
A key characteristic of sickle cell anemia is:
RBCs that form sickle shapes under low-oxygen conditions ## Footnote Sickle cell anemia is caused by abnormal hemoglobin that polymerizes under low oxygen tension.
39
Which of the following can cause secondary polycythemia?
High altitude living conditions ## Footnote Chronic hypoxia from high altitude increases EPO production, leading to more RBCs.
40
The majority of RBC energy (ATP) is generated via:
Glycolysis in the cytoplasm ## Footnote RBCs lack mitochondria and rely on anaerobic glycolysis for ATP.
41
Which protein in RBC membranes maintains their biconcave shape?
Spectrin ## Footnote Spectrin is a cytoskeletal protein essential for RBC membrane elasticity and shape.
42
In the absence of adequate iron, the RBCs formed will have:
Reduced hemoglobin content ## Footnote Iron is required for hemoglobin synthesis; without it, RBCs are hypochromic and microcytic.
43
When RBCs are destroyed, the iron released from hemoglobin is:
Stored as ferritin or hemosiderin for reuse ## Footnote The body efficiently recycles iron, storing it for future hemoglobin synthesis.
44
The primary stimulus for increased RBC production in secondary polycythemia is:
Low partial pressure of oxygen in tissues ## Footnote Chronic hypoxia triggers increased EPO secretion, leading to more RBCs.
45
In macrocytic anemias, RBCs are larger because of:
Impaired DNA synthesis leading to delayed nuclear maturation ## Footnote Macrocytosis arises from deficiencies in folate or B12, causing slow nuclear maturation.
46
The term 'hematopoiesis' refers to:
Production of blood cells ## Footnote Hematopoiesis involves the formation and development of all blood cell types.
47
What does the term 'hematopoiesis' refer to?
Production of blood cells ## Footnote Hematopoiesis means formation and development of all blood cell types.
48
In the early embryo, where are the first RBCs formed?
Yolk sac ## Footnote Primitive erythropoiesis begins in the yolk sac during early embryonic life.
49
Which cells secrete the intrinsic factor necessary for vitamin B12 absorption?
Parietal cells of the stomach ## Footnote Parietal cells secrete intrinsic factor, required for B12 absorption in the ileum.
50
Hematopoietic stem cells in the bone marrow give rise to which types of blood cells?
RBCs, WBCs, and platelets ## Footnote Hematopoietic stem cells are multipotent and can differentiate into all blood cell lineages.
51
Why can't RBCs repair themselves?
They have no DNA or nucleus ## Footnote Mature RBCs lack a nucleus and organelles, preventing protein synthesis or damage repair.
52
Which condition results in RBCs that are abnormally fragile and prone to rupture?
Hereditary spherocytosis ## Footnote Caused by defects in RBC cytoskeleton proteins, leading to spherical, fragile RBCs.
53
A patient with high RBC count and low EPO levels most likely has what condition?
Polycythemia vera ## Footnote A primary polycythemia where RBCs proliferate independently, often with low EPO due to negative feedback.
54
Which glycolytic intermediate regulates oxygen release from hemoglobin?
2,3-Bisphosphoglycerate (2,3-BPG) ## Footnote 2,3-BPG binds to deoxyhemoglobin, stabilizing it and facilitating oxygen release to tissues.
55
Which RBC membrane protein is crucial for anchoring the spectrin-actin cytoskeleton?
Ankyrin ## Footnote Ankyrin links spectrin to band 3 proteins in the RBC membrane, maintaining RBC shape and deformability.
56
Which index measures the variation in RBC size?
RDW (Red Cell Distribution Width) ## Footnote RDW indicates the variation in RBC size; a high RDW suggests a wide range of cell sizes.
57
What is the earliest recognizable precursor of the RBC lineage in the bone marrow?
Proerythroblast ## Footnote The proerythroblast is the first morphologically identifiable RBC precursor in the marrow.
58
What does poikilocytosis refer to?
Variation in RBC shape ## Footnote Poikilocytosis is abnormal variation in RBC shape.
59
During early fetal life, the primary site of hematopoiesis transitions from the yolk sac to the:
Liver ## Footnote After initial hematopoiesis in the yolk sac, the fetal liver becomes the main site of RBC production.
60
Which RBC enzyme pathway provides NADPH to maintain reduced glutathione?
Hexose monophosphate (pentose phosphate) shunt ## Footnote This pathway generates NADPH to keep glutathione reduced, protecting RBCs from oxidative damage.
61
What triggers macrophages in the spleen to phagocytose aged RBCs?
Changes in RBC membrane carbohydrates and exposure of phosphatidylserine ## Footnote Aging RBCs show altered membrane patterns, signaling splenic macrophages for removal.
62
How do RBCs assist in acid-base balance?
Carbonic anhydrase converting CO2 to bicarbonate and H+ ## Footnote This reaction facilitates CO2 transport and buffering in the blood.
63
Relative polycythemia can occur due to:
Dehydration reducing plasma volume ## Footnote This results in an apparent increase in RBC count due to decreased plasma volume.
64
Which RBC index reflects the concentration of hemoglobin in a given volume of RBCs?
MCHC (Mean Corpuscular Hemoglobin Concentration) ## Footnote MCHC measures the concentration of hemoglobin per unit volume of RBCs.
65
One of the key characteristics of extravascular hemolysis is:
RBC destruction primarily by macrophages in the spleen and liver ## Footnote Extravascular hemolysis occurs within macrophages, not free in the bloodstream.
66
In intravascular hemolysis, free hemoglobin released into blood is bound by:
Haptoglobin ## Footnote Haptoglobin binds free hemoglobin in plasma, preventing kidney damage and iron loss.
67
Lead poisoning affects RBCs by inhibiting which process?
Heme synthesis enzymes, leading to basophilic stippling ## Footnote Lead inhibits enzymes like ferrochelatase and ALA dehydratase, causing abnormal RBCs.
68
The reticulocyte production index (RPI) adjusts the reticulocyte count for:
Degree of anemia and RBC lifespan ## Footnote RPI corrects the reticulocyte percentage to account for the severity of anemia.
69
Which abnormal RBC form is characteristically seen in hereditary spherocytosis?
Spherocytes ## Footnote Hereditary spherocytosis is due to membrane skeletal protein defects leading to spherical RBCs.
70
What causes hereditary spherocytosis?
Defects in membrane skeletal proteins leading to spherical RBCs ## Footnote Hereditary spherocytosis results in a characteristic shape change in red blood cells.
71
What happens to stored RBCs in blood banks over time?
Decreased ATP and 2,3-BPG levels, reducing O2 delivery capacity ## Footnote Stored RBCs lose energy and their ability to efficiently release oxygen.
72
An elevated RDW (Red Cell Distribution Width) is commonly associated with what?
A mixed population of microcytic and normocytic RBCs ## Footnote High RDW indicates variability in red blood cell sizes, often seen during treatment for iron deficiency.
73
A high MCHC (Mean Corpuscular Hemoglobin Concentration) is most commonly seen in which condition?
Hereditary spherocytosis ## Footnote Higher MCHC occurs due to the spherical shape and reduced volume of RBCs.
74
The presence of target cells (codocytes) is associated with which conditions?
Liver disease, thalassemia, and hemoglobinopathies ## Footnote Target cells can be seen in various conditions affecting hemoglobin and cell morphology.
75
Basophilic stippling of RBCs is commonly observed in what?
Lead poisoning and thalassemia ## Footnote This stippling indicates impaired maturation of red blood cells.
76
What is the key effect of increasing RBC 2,3-BPG levels at high altitude?
Increased oxygen delivery to tissues ## Footnote Elevated 2,3-BPG reduces hemoglobin's affinity for oxygen, promoting better oxygen release.
77
In the embryo, the very first RBCs formed in the yolk sac are characterized by what?
Primitive nucleated erythrocytes with embryonic hemoglobins ## Footnote These early RBCs are different from adult hemoglobins and are involved in early oxygen transport.
78
RBC deformability is critical for what function?
Allowing RBCs to pass through narrow capillaries ## Footnote Deformability is essential for effective oxygen delivery in the microcirculation.
79
When RBCs are destroyed intravascularly, what is a possible clinical sign?
Hemoglobinuria and hemosiderinuria ## Footnote Free hemoglobin released into plasma and urine indicates intravascular hemolysis.
80
Which condition is characterized by defective synthesis of globin chains leading to microcytosis?
Thalassemia ## Footnote Thalassemia results in microcytic anemia due to impaired globin chain production.
81
Iron overload can lead to what physiological response?
Increased hepcidin levels to limit iron absorption ## Footnote Hepcidin regulates iron homeostasis, especially during overload conditions.
82
RBC aging is often marked by a decrease in what?
Enzyme activity and ATP levels ## Footnote Aging RBCs lose functionality and signaling for removal as energy levels drop.
83
Which organ primarily monitors and removes aged RBCs from circulation?
Spleen (red pulp macrophages) ## Footnote The spleen plays a crucial role in filtering and phagocytosing senescent red blood cells.
84
In anemia of chronic disease, increased hepcidin traps iron in storage sites, which reduces what?
Availability for RBC production ## Footnote This mechanism contributes to anemia by limiting iron necessary for erythropoiesis.
85
A 'shift to the right' in the oxygen-hemoglobin dissociation curve is facilitated by what?
RBCs release 2,3-BPG, decreasing Hb’s oxygen affinity ## Footnote This shift enhances oxygen release to tissues, especially under hypoxic conditions.
86
In sickle cell disease, the mutation in the beta-globin chain replaces which amino acid?
Glutamic acid with valine ## Footnote This specific mutation leads to the sickling of red blood cells under low oxygen conditions.
87
In sideroblastic anemia, ringed sideroblasts form because?
Iron cannot be incorporated into heme properly ## Footnote This defect leads to abnormal erythroblast maturation and iron accumulation.
88
RBC lifespan in circulation is maintained despite no nucleus by what?
Stable enzyme systems and membrane maintenance pathways ## Footnote RBCs rely on long-lived enzymes for functionality throughout their lifespan.
89
The pentose phosphate pathway in RBCs mainly serves to produce what?
NADPH to maintain reduced glutathione ## Footnote This function protects RBCs from oxidative damage.
90
Erythropoiesis-stimulating agents (ESAs) can cause what?
Increased RBC mass and possibly elevated blood viscosity ## Footnote ESAs stimulate RBC production, which may lead to increased hematocrit.
91
What is the normal adult hemoglobin (HbA) composition?
α2β2 ## Footnote This composition is essential for normal oxygen transport in the blood.
92
In anemia of chronic disease, iron is sequestered in storage sites due to what?
Increased hepcidin levels ## Footnote Hepcidin's role is crucial in regulating iron availability for erythropoiesis.
93
In anemia of chronic disease, iron is sequestered in storage sites due to?
Increased hepcidin levels ## Footnote Hepcidin blocks iron release from macrophages and enterocytes, leading to sequestration.
94
In polycythemia vera, the mutation often found is in?
The JAK2 tyrosine kinase ## Footnote Polycythemia vera frequently involves a JAK2 mutation, leading to erythrocytosis independent of EPO.
95
RBC fragility tests measure?
The strength of RBC membranes under hypotonic conditions ## Footnote Osmotic fragility tests assess RBC membrane stability in hypotonic solutions.
96
RBC sedimentation rate (ESR) increases when?
Plasma fibrinogen and globulins increase, reducing RBC repulsion ## Footnote Increased fibrinogen and other acute-phase reactants cause RBCs to stack (rouleaux), increasing ESR.
97
The RBC’s unique biconcave shape helps by?
Increasing surface-to-volume ratio for efficient gas exchange ## Footnote The biconcave shape increases surface area relative to volume, aiding rapid gas diffusion.
98
Carbon monoxide (CO) interferes with RBC function by?
Displacing O2 from hemoglobin with higher affinity ## Footnote CO binds hemoglobin with much greater affinity than O2, impairing O2 delivery.
99
A decrease in plasma volume (as in dehydration) without a change in RBC mass results in?
Relative polycythemia ## Footnote Reduced plasma volume elevates hematocrit, appearing as polycythemia but RBC mass is unchanged.
100
The body’s inability to excrete excess iron easily leads to?
Iron loading in tissues (hemochromatosis) ## Footnote With no regulated excretion route, excess iron accumulates, causing tissue damage.
101
The hormone EPO acts on which cells in the bone marrow?
Progenitor and precursor cells in the erythroid lineage ## Footnote EPO stimulates erythroid progenitors (CFU-E) and precursors to proliferate and differentiate.
102
In G6PD deficiency, RBCs are more susceptible to oxidative stress because?
They have reduced glutathione levels due to less NADPH ## Footnote G6PD deficiency impairs the pentose phosphate pathway, reducing NADPH and thus glutathione, increasing oxidative damage risk.
103
In anemia of chronic disease, serum iron is often low because?
Hepcidin blocks iron release from macrophages and intestinal cells ## Footnote Hepcidin sequesters iron in storage sites, reducing serum iron despite adequate stores.
104
The lifespan of stored RBCs after transfusion is?
Often reduced due to storage lesion-related damage ## Footnote Storage lesions cause reduced RBC deformability and shortened post-transfusion survival.
105
Effective erythropoiesis ensures that?
Iron, vitamin B12, and folate availability match RBC production needs ## Footnote Successful erythropoiesis depends on adequate supplies of iron, B12, and folate, as well as appropriate hormone regulation.
106
What is the average life span of a normal red blood cell in the circulation?
120 days ## Footnote Normal red blood cells survive about 120 days before being removed by the spleen.
107
Which organ is most responsible for releasing erythropoietin (EPO) in response to hypoxia?
Kidney ## Footnote The kidney's interstitial fibroblasts are the primary source of erythropoietin.
108
What is the shape of mature red blood cells?
Biconcave discs without nuclei ## Footnote RBCs lack nuclei and most organelles, maximizing surface area for gas exchange.
109
What is the primary function of red blood cells?
Transport oxygen and carbon dioxide ## Footnote RBCs carry oxygen from the lungs to tissues and facilitate carbon dioxide transport back.
110
Hemoglobin is primarily composed of?
Four globin chains and four heme groups ## Footnote Adult hemoglobin consists of two alpha and two beta globin chains, each with a heme group.
111
Which form of hemoglobin binds oxygen most readily?
Oxyhemoglobin ## Footnote Oxyhemoglobin is hemoglobin that is bound to oxygen.
112
Iron is absorbed primarily in which part of the gastrointestinal tract?
Duodenum ## Footnote The duodenum is the primary site of iron absorption.
113
Which cell type eventually becomes a mature RBC in the peripheral blood?
Reticulocyte ## Footnote Reticulocytes are immature RBCs that mature into erythrocytes within about 1-2 days.
114
Erythropoietin production is stimulated by?
Low oxygen levels ## Footnote Hypoxia in the kidney stimulates erythropoietin secretion.
115
The most important regulator of RBC production is?
Erythropoietin ## Footnote Erythropoietin is the key hormone regulating RBC production in the bone marrow.
116
Which nutrient deficiency leads to megaloblastic anemia?
Vitamin B12 and folate ## Footnote Deficiencies in vitamin B12 or folic acid impair DNA synthesis, causing megaloblastic anemia.
117
What is the role of transferrin in iron metabolism?
Transport of iron in the blood ## Footnote Transferrin binds and transports iron through the bloodstream to tissues.
118
The majority of iron in the body is found in?
Hemoglobin in RBCs ## Footnote About two-thirds of the body's iron is in the heme structure of hemoglobin.
119
A low reticulocyte count in a patient with anemia suggests?
Reduced RBC production ## Footnote A low reticulocyte count indicates inadequate bone marrow response.
120
Iron deficiency anemia typically presents as?
Microcytic, hypochromic anemia ## Footnote Iron deficiency leads to smaller RBCs that are paler due to reduced hemoglobin content.
121
Pernicious anemia is caused by a deficiency of?
Intrinsic factor leading to B12 malabsorption ## Footnote Pernicious anemia results from autoimmune gastritis that reduces intrinsic factor.
122
The normal red blood cell count in men is approximately?
5 million/µL ## Footnote Normal RBC count for men averages around 5.2 million/µL.
123
Bilirubin is formed from the breakdown of?
The heme portion of hemoglobin ## Footnote Heme is degraded to biliverdin and then bilirubin when RBCs are destroyed.
124
Polycythemia vera is characterized by?
Increased RBC mass due to a myeloproliferative disorder ## Footnote Polycythemia vera is a bone marrow disorder causing excessive RBC production.
125
In response to chronic hypoxia, the body compensates by?
Increasing RBC production ## Footnote Chronic hypoxia stimulates the kidney to produce more EPO, leading to increased RBC production.
126
The key regulator of iron absorption from the gut is?
Hepcidin ## Footnote Hepcidin regulates intestinal iron absorption and release from stores.
127
Aplastic anemia involves?
Failure of the bone marrow to produce RBCs ## Footnote Aplastic anemia results from inadequate hematopoiesis in the bone marrow.
128
What does ferritin do?
Stores iron, doesn’t regulate absorption directly ## Footnote Ferritin is a protein that serves as a storage form of iron in the body.
129
What is aplastic anemia?
Failure of the bone marrow to produce RBCs ## Footnote Aplastic anemia results in insufficient production of all blood cell types, including red blood cells.
130
Which substance is crucial for DNA synthesis in RBC precursors?
Vitamin B12 ## Footnote Vitamin B12 deficiency can lead to megaloblastic anemia due to impaired RBC maturation.
131
The oxygen-carrying capacity of blood is directly proportional to:
The hemoglobin concentration ## Footnote More hemoglobin means a greater capacity to carry oxygen in the blood.
132
Which condition leads to normocytic, normochromic anemia?
Acute blood loss ## Footnote Acute hemorrhage initially presents as normocytic, normochromic anemia before compensatory changes occur.
133
Hemolytic anemias are characterized by:
Increased RBC destruction ## Footnote Hemolytic anemia involves the premature destruction of RBCs, leading to elevated bilirubin levels.
134
Carbonic anhydrase in RBCs facilitates:
Conversion of CO2 and H2O into H2CO3 ## Footnote This reaction aids in the transport of carbon dioxide in the blood.
135
The normal hematocrit for a healthy adult male is approximately:
45% ## Footnote Normal male hematocrit is around 40-50%, with 45% being a common value.
136
In iron deficiency anemia, serum ferritin levels are typically:
Low ## Footnote Ferritin levels drop in iron deficiency as it reflects body iron stores.
137
Excessive RBC destruction often leads to:
Jaundice (increased bilirubin) ## Footnote Hemolysis increases free bilirubin load in the body, which can cause jaundice.
138
Hemoglobin F (fetal hemoglobin) differs from adult hemoglobin (HbA) because it:
Has a higher affinity for oxygen ## Footnote This higher affinity facilitates oxygen transfer from maternal to fetal blood.
139
The final step in heme synthesis occurs in the:
Mitochondria of RBC precursors ## Footnote Heme synthesis begins in the mitochondria, moves to the cytosol, and ends back in the mitochondria.
140
Iron overload (hemochromatosis) can damage organs due to:
Iron-mediated oxidative stress ## Footnote Excess iron can lead to the formation of free radicals, causing tissue damage.
141
The normal mean corpuscular volume (MCV) for RBCs is approximately:
80-100 fL ## Footnote Normal MCV indicates the average size of RBCs; values outside this range suggest microcytosis or macrocytosis.
142
Chronic renal failure often leads to anemia because:
The kidneys produce inadequate EPO ## Footnote Damaged kidneys do not produce sufficient erythropoietin (EPO), reducing RBC production.
143
A key characteristic of sickle cell anemia is:
RBCs that form sickle shapes under low-oxygen conditions ## Footnote Sickle cell anemia is caused by abnormal hemoglobin that polymerizes under low oxygen tension.
144
Which of the following can cause secondary polycythemia?
High altitude living conditions ## Footnote Chronic hypoxia from high altitude increases EPO production, leading to more RBCs.
145
The majority of RBC energy (ATP) is generated via:
Glycolysis in the cytoplasm ## Footnote RBCs lack mitochondria and rely on anaerobic glycolysis for ATP.
146
Which protein in RBC membranes maintains their biconcave shape?
Spectrin ## Footnote Spectrin is a cytoskeletal protein essential for RBC membrane elasticity and shape.
147
In the absence of adequate iron, the RBCs formed will have:
Reduced hemoglobin content ## Footnote Iron is required for hemoglobin synthesis; without it, RBCs are hypochromic and microcytic.
148
When RBCs are destroyed, the iron released from hemoglobin is:
Stored as ferritin or hemosiderin for reuse ## Footnote The body efficiently recycles iron, storing it for future hemoglobin synthesis.
149
The primary stimulus for increased RBC production in secondary polycythemia is:
Low partial pressure of oxygen in tissues ## Footnote Chronic hypoxia triggers increased EPO secretion, leading to more RBCs.
150
In macrocytic anemias, RBCs are larger because of:
Impaired DNA synthesis leading to delayed nuclear maturation ## Footnote Macrocytosis arises from deficiencies in folate or B12, causing slow nuclear maturation.
151
The term 'hematopoiesis' refers to:
Production of blood cells ## Footnote Hematopoiesis involves the formation and development of all blood cell types.
152
What does the term 'hematopoiesis' refer to?
Production of blood cells ## Footnote Hematopoiesis means formation and development of all blood cell types.
153
In the early embryo, where are the first RBCs formed?
Yolk sac ## Footnote Primitive erythropoiesis begins in the yolk sac during early embryonic life.
154
Which cells secrete the intrinsic factor necessary for vitamin B12 absorption?
Parietal cells of the stomach ## Footnote Parietal cells secrete intrinsic factor, required for B12 absorption in the ileum.
155
Hematopoietic stem cells in the bone marrow give rise to which types of blood cells?
RBCs, WBCs, and platelets ## Footnote Hematopoietic stem cells are multipotent and can differentiate into all blood cell lineages.
156
Why can't RBCs repair themselves?
They have no DNA or nucleus ## Footnote Mature RBCs lack a nucleus and organelles, preventing protein synthesis or damage repair.
157
Which condition results in RBCs that are abnormally fragile and prone to rupture?
Hereditary spherocytosis ## Footnote Caused by defects in RBC cytoskeleton proteins, leading to spherical, fragile RBCs.
158
A patient with high RBC count and low EPO levels most likely has what condition?
Polycythemia vera ## Footnote A primary polycythemia where RBCs proliferate independently, often with low EPO due to negative feedback.
159
Which glycolytic intermediate regulates oxygen release from hemoglobin?
2,3-Bisphosphoglycerate (2,3-BPG) ## Footnote 2,3-BPG binds to deoxyhemoglobin, stabilizing it and facilitating oxygen release to tissues.
160
Which RBC membrane protein is crucial for anchoring the spectrin-actin cytoskeleton?
Ankyrin ## Footnote Ankyrin links spectrin to band 3 proteins in the RBC membrane, maintaining RBC shape and deformability.
161
Which index measures the variation in RBC size?
RDW (Red Cell Distribution Width) ## Footnote RDW indicates the variation in RBC size; a high RDW suggests a wide range of cell sizes.
162
What is the earliest recognizable precursor of the RBC lineage in the bone marrow?
Proerythroblast ## Footnote The proerythroblast is the first morphologically identifiable RBC precursor in the marrow.
163
What does poikilocytosis refer to?
Variation in RBC shape ## Footnote Poikilocytosis is abnormal variation in RBC shape.
164
During early fetal life, the primary site of hematopoiesis transitions from the yolk sac to the:
Liver ## Footnote After initial hematopoiesis in the yolk sac, the fetal liver becomes the main site of RBC production.
165
Which RBC enzyme pathway provides NADPH to maintain reduced glutathione?
Hexose monophosphate (pentose phosphate) shunt ## Footnote This pathway generates NADPH to keep glutathione reduced, protecting RBCs from oxidative damage.
166
What triggers macrophages in the spleen to phagocytose aged RBCs?
Changes in RBC membrane carbohydrates and exposure of phosphatidylserine ## Footnote Aging RBCs show altered membrane patterns, signaling splenic macrophages for removal.
167
How do RBCs assist in acid-base balance?
Carbonic anhydrase converting CO2 to bicarbonate and H+ ## Footnote This reaction facilitates CO2 transport and buffering in the blood.
168
Relative polycythemia can occur due to:
Dehydration reducing plasma volume ## Footnote This results in an apparent increase in RBC count due to decreased plasma volume.
169
Which RBC index reflects the concentration of hemoglobin in a given volume of RBCs?
MCHC (Mean Corpuscular Hemoglobin Concentration) ## Footnote MCHC measures the concentration of hemoglobin per unit volume of RBCs.
170
One of the key characteristics of extravascular hemolysis is:
RBC destruction primarily by macrophages in the spleen and liver ## Footnote Extravascular hemolysis occurs within macrophages, not free in the bloodstream.
171
In intravascular hemolysis, free hemoglobin released into blood is bound by:
Haptoglobin ## Footnote Haptoglobin binds free hemoglobin in plasma, preventing kidney damage and iron loss.
172
Lead poisoning affects RBCs by inhibiting which process?
Heme synthesis enzymes, leading to basophilic stippling ## Footnote Lead inhibits enzymes like ferrochelatase and ALA dehydratase, causing abnormal RBCs.
173
The reticulocyte production index (RPI) adjusts the reticulocyte count for:
Degree of anemia and RBC lifespan ## Footnote RPI corrects the reticulocyte percentage to account for the severity of anemia.
174
Which abnormal RBC form is characteristically seen in hereditary spherocytosis?
Spherocytes ## Footnote Hereditary spherocytosis is due to membrane skeletal protein defects leading to spherical RBCs.
175
What causes hereditary spherocytosis?
Defects in membrane skeletal proteins leading to spherical RBCs ## Footnote Hereditary spherocytosis results in a characteristic shape change in red blood cells.
176
What happens to stored RBCs in blood banks over time?
Decreased ATP and 2,3-BPG levels, reducing O2 delivery capacity ## Footnote Stored RBCs lose energy and their ability to efficiently release oxygen.
177
An elevated RDW (Red Cell Distribution Width) is commonly associated with what?
A mixed population of microcytic and normocytic RBCs ## Footnote High RDW indicates variability in red blood cell sizes, often seen during treatment for iron deficiency.
178
A high MCHC (Mean Corpuscular Hemoglobin Concentration) is most commonly seen in which condition?
Hereditary spherocytosis ## Footnote Higher MCHC occurs due to the spherical shape and reduced volume of RBCs.
179
The presence of target cells (codocytes) is associated with which conditions?
Liver disease, thalassemia, and hemoglobinopathies ## Footnote Target cells can be seen in various conditions affecting hemoglobin and cell morphology.
180
Basophilic stippling of RBCs is commonly observed in what?
Lead poisoning and thalassemia ## Footnote This stippling indicates impaired maturation of red blood cells.
181
What is the key effect of increasing RBC 2,3-BPG levels at high altitude?
Increased oxygen delivery to tissues ## Footnote Elevated 2,3-BPG reduces hemoglobin's affinity for oxygen, promoting better oxygen release.
182
In the embryo, the very first RBCs formed in the yolk sac are characterized by what?
Primitive nucleated erythrocytes with embryonic hemoglobins ## Footnote These early RBCs are different from adult hemoglobins and are involved in early oxygen transport.
183
RBC deformability is critical for what function?
Allowing RBCs to pass through narrow capillaries ## Footnote Deformability is essential for effective oxygen delivery in the microcirculation.
184
When RBCs are destroyed intravascularly, what is a possible clinical sign?
Hemoglobinuria and hemosiderinuria ## Footnote Free hemoglobin released into plasma and urine indicates intravascular hemolysis.
185
Which condition is characterized by defective synthesis of globin chains leading to microcytosis?
Thalassemia ## Footnote Thalassemia results in microcytic anemia due to impaired globin chain production.
186
Iron overload can lead to what physiological response?
Increased hepcidin levels to limit iron absorption ## Footnote Hepcidin regulates iron homeostasis, especially during overload conditions.
187
RBC aging is often marked by a decrease in what?
Enzyme activity and ATP levels ## Footnote Aging RBCs lose functionality and signaling for removal as energy levels drop.
188
Which organ primarily monitors and removes aged RBCs from circulation?
Spleen (red pulp macrophages) ## Footnote The spleen plays a crucial role in filtering and phagocytosing senescent red blood cells.
189
In anemia of chronic disease, increased hepcidin traps iron in storage sites, which reduces what?
Availability for RBC production ## Footnote This mechanism contributes to anemia by limiting iron necessary for erythropoiesis.
190
A 'shift to the right' in the oxygen-hemoglobin dissociation curve is facilitated by what?
RBCs release 2,3-BPG, decreasing Hb’s oxygen affinity ## Footnote This shift enhances oxygen release to tissues, especially under hypoxic conditions.
191
In sickle cell disease, the mutation in the beta-globin chain replaces which amino acid?
Glutamic acid with valine ## Footnote This specific mutation leads to the sickling of red blood cells under low oxygen conditions.
192
In sideroblastic anemia, ringed sideroblasts form because?
Iron cannot be incorporated into heme properly ## Footnote This defect leads to abnormal erythroblast maturation and iron accumulation.
193
RBC lifespan in circulation is maintained despite no nucleus by what?
Stable enzyme systems and membrane maintenance pathways ## Footnote RBCs rely on long-lived enzymes for functionality throughout their lifespan.
194
The pentose phosphate pathway in RBCs mainly serves to produce what?
NADPH to maintain reduced glutathione ## Footnote This function protects RBCs from oxidative damage.
195
Erythropoiesis-stimulating agents (ESAs) can cause what?
Increased RBC mass and possibly elevated blood viscosity ## Footnote ESAs stimulate RBC production, which may lead to increased hematocrit.
196
What is the normal adult hemoglobin (HbA) composition?
α2β2 ## Footnote This composition is essential for normal oxygen transport in the blood.
197
In anemia of chronic disease, iron is sequestered in storage sites due to what?
Increased hepcidin levels ## Footnote Hepcidin's role is crucial in regulating iron availability for erythropoiesis.
198
In anemia of chronic disease, iron is sequestered in storage sites due to?
Increased hepcidin levels ## Footnote Hepcidin blocks iron release from macrophages and enterocytes, leading to sequestration.
199
In polycythemia vera, the mutation often found is in?
The JAK2 tyrosine kinase ## Footnote Polycythemia vera frequently involves a JAK2 mutation, leading to erythrocytosis independent of EPO.
200
RBC fragility tests measure?
The strength of RBC membranes under hypotonic conditions ## Footnote Osmotic fragility tests assess RBC membrane stability in hypotonic solutions.
201
RBC sedimentation rate (ESR) increases when?
Plasma fibrinogen and globulins increase, reducing RBC repulsion ## Footnote Increased fibrinogen and other acute-phase reactants cause RBCs to stack (rouleaux), increasing ESR.
202
The RBC’s unique biconcave shape helps by?
Increasing surface-to-volume ratio for efficient gas exchange ## Footnote The biconcave shape increases surface area relative to volume, aiding rapid gas diffusion.
203
Carbon monoxide (CO) interferes with RBC function by?
Displacing O2 from hemoglobin with higher affinity ## Footnote CO binds hemoglobin with much greater affinity than O2, impairing O2 delivery.
204
A decrease in plasma volume (as in dehydration) without a change in RBC mass results in?
Relative polycythemia ## Footnote Reduced plasma volume elevates hematocrit, appearing as polycythemia but RBC mass is unchanged.
205
The body’s inability to excrete excess iron easily leads to?
Iron loading in tissues (hemochromatosis) ## Footnote With no regulated excretion route, excess iron accumulates, causing tissue damage.
206
The hormone EPO acts on which cells in the bone marrow?
Progenitor and precursor cells in the erythroid lineage ## Footnote EPO stimulates erythroid progenitors (CFU-E) and precursors to proliferate and differentiate.
207
In G6PD deficiency, RBCs are more susceptible to oxidative stress because?
They have reduced glutathione levels due to less NADPH ## Footnote G6PD deficiency impairs the pentose phosphate pathway, reducing NADPH and thus glutathione, increasing oxidative damage risk.
208
In anemia of chronic disease, serum iron is often low because?
Hepcidin blocks iron release from macrophages and intestinal cells ## Footnote Hepcidin sequesters iron in storage sites, reducing serum iron despite adequate stores.
209
The lifespan of stored RBCs after transfusion is?
Often reduced due to storage lesion-related damage ## Footnote Storage lesions cause reduced RBC deformability and shortened post-transfusion survival.
210
Effective erythropoiesis ensures that?
Iron, vitamin B12, and folate availability match RBC production needs ## Footnote Successful erythropoiesis depends on adequate supplies of iron, B12, and folate, as well as appropriate hormone regulation.

Guyton And Hall Physiology (1 decks)

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