Iron Transport and Storage in the Body

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Questions and Answers

What role does erythropoietin play in red blood cell production?

Inhibits the production of proerythroblasts from stem cells.

Reduces the lifespan of circulating red blood cells.

Stimulates the transformation of proerythroblasts into mature red blood cells.

Promotes the rapid progression of proerythroblasts through the erythroblastic stages. (correct)

What is the consequence of removing both kidneys from a person?

They produce erythropoietin at a normal level from other tissues.

They develop severe anemia due to insufficient erythropoietin production. (correct)

They experience an increase in red blood cell count.

They can produce enough erythropoietin from the liver.

What percentage of the normal erythropoietin production can the liver provide in the absence of kidneys?

10% (correct)

50%

25%

75%

What happens to red blood cells after their average lifespan of 120 days?

They are typically removed from circulation. Signup and view all the answers

In addition to the kidneys, which organ contributes to the formation of erythropoietin?

Liver Signup and view all the answers

Why are mature red blood cells unable to synthesize proteins?

They are non-nucleated. Signup and view all the answers

What metabolic activity can mature red blood cells perform despite lacking organelles?

Metabolizing glucose and forming ATP. Signup and view all the answers

What initiates the release of erythropoietin when hypoxia occurs in the body?

Signals from nonrenal sensors detecting low oxygen levels. Signup and view all the answers

What is the primary characteristic of basophil erythroblasts?

They stain with basic dyes. Signup and view all the answers

What is the fate of the nucleus in the later stages of erythroblast development?

It condenses to a small size. Signup and view all the answers

What is the molecular weight of erythropoietin?

34,000 Signup and view all the answers

In which state is erythropoietin primarily stimulated for red blood cell production?

Low oxygen states. Signup and view all the answers

What happens to hematocrit levels when erythropoietin is active due to tissue hypoxia?

Hematocrit levels increase. Signup and view all the answers

What effect does the absence of erythropoietin have on red blood cell production?

It has little or no effect on red blood cell production. Signup and view all the answers

What is the main role of erythropoietin in the body?

To stimulate red blood cell production. Signup and view all the answers

During the development of erythroblasts, what happens to the endoplasmic reticulum?

It is reabsorbed. Signup and view all the answers

What physiological condition leads to secondary polycythemia due to hypoxia?

Cardiac failure Signup and view all the answers

What is the normal red blood cell count (RBC) range for a healthy individual in million/mm3?

4 to 5 million/mm3 Signup and view all the answers

What is a characteristic of polycythemia vera regarding the hematocrit percentage?

Increases to 60 to 70 percent Signup and view all the answers

How does secondary polycythemia enable natives at high altitudes to perform strenuous tasks?

Higher red blood cell count Signup and view all the answers

What effect does increased blood viscosity have on circulation?

Slows down blood flow in peripheral vessels Signup and view all the answers

What is the cause of polycythemia vera?

Genetic aberration in blood cell production Signup and view all the answers

What happens to the total blood volume in the case of polycythemia vera?

Increases, sometimes to almost double normal Signup and view all the answers

What is a major consequence of blood capillaries becoming plugged in polycythemia vera?

Reduced oxygen delivery to tissues Signup and view all the answers

What is a primary reason some hematologists prefer the absolute retic count over the retic index?

The retic index is based on outdated data. Signup and view all the answers

How does severe anemia affect blood viscosity compared to normal levels?

Blood viscosity can drop to as low as 1.5 times that of water. Signup and view all the answers

What does the MCV and retic index categorization primarily aim to assist with?

Diagnosing the etiology of anemia. Signup and view all the answers

What visual sign may indicate a person with polycythemia vera?

Cyanotic skin with a reddish appearance. Signup and view all the answers

Which factor complicates the categorization of anemia based on MCV and retic index?

The approximative nature of established cutoffs. Signup and view all the answers

In what manner do blood flow characteristics change in severe anemia?

Blood flow increases as viscosity decreases, raising cardiac output. Signup and view all the answers

What may be a consequence if the body's regulatory mechanisms for blood viscosity fail?

Hypertension may develop. Signup and view all the answers

Which of the following statements about the retic index is correct?

It may include maturation factors in its calculation. Signup and view all the answers

What role does transferrin play in iron metabolism?

Transferrin binds to receptors in erythroblasts to facilitate iron intake. Signup and view all the answers

What happens when transferrin levels are inadequate in the blood?

Iron transportation to erythroblasts is impaired, leading to anemia. Signup and view all the answers

Where does transferrin deliver iron after it binds to erythroblasts?

To the mitochondria for heme synthesis. Signup and view all the answers

What occurs when there is a low quantity of iron in plasma?

Ferritin iron is mobilized and transported in plasma as transferrin. Signup and view all the answers

What is a characteristic feature of transferrin?

It has a strong binding affinity to erythroblast receptors. Signup and view all the answers

Which condition can result from inadequate transport of iron to erythroblasts?

Hypochromic anemia characterized by low hemoglobin levels. Signup and view all the answers

In which organelle is heme synthesized after iron is delivered by transferrin?

Mitochondria Signup and view all the answers

What can blood saturation with iron indicate about apoferritin?

All apoferritin in storage areas is likely saturated with iron. Signup and view all the answers

Study Notes

Iron Transport and Function

Low plasma iron levels prompt the release of iron from ferritin storage, transported as transferrin to target areas.
Transferrin binds strongly to receptors on erythroblast cell membranes in the bone marrow, facilitating iron uptake.
Erythroblasts ingest transferrin-bound iron through endocytosis, directing it to mitochondria for heme synthesis.
Insufficient transferrin leads to severe hypochromic anemia, resulting in red blood cells with reduced hemoglobin content.

Erythropoietin (EPO) Regulation

Basophil erythroblasts, early-stage red blood cells, initially contain little hemoglobin and stain with basic dyes.
Subsequent erythroblast maturation involves hemoglobin accumulation (approximately 34% concentration) and nucleus condensation.
EPO, a glycoprotein with a molecular weight of 34,000, serves as the principal stimulus for red blood cell formation during low oxygen states.
EPO secretion can be influenced by hypoxia in body regions other than the kidneys, indicating potential nonrenal signals for hormone production.
Absence of adequate EPO (after kidney removal or renal disease) leads to significant anemia, producing only one-third to one-half of the required red blood cells.

Red Blood Cell Lifespan and Composition

Red blood cells, upon release from the bone marrow, have an average lifespan of 120 days before destruction.
Though mature red blood cells lack a nucleus, they possess cytoplasmic enzymes aiding glucose metabolism and ATP production.

Anemia and Reticulocyte Index

Diagnostic evaluation for anemia typically involves the mean corpuscular volume (MCV) and reticulocyte index.
MCV categorization based on red blood cell size and maturity factors should be viewed as approximate due to Limited replicable data.
Some hematologists prefer using absolute reticulocyte counts (retic % x RBC count) over the reticulocyte index for diagnosis.

Effects of Anemia on Circulation

Severe anemia can reduce blood viscosity to as low as 1.5 times that of water, versus a normal value of about 3.
Lower viscosity decreases peripheral resistance, allowing excessive blood circulation and increased cardiac output.
Deoxygenated hemoglobin may give skin a cyanotic tint, notably visible in conditions like polycythemia vera, where the complexion appears ruddy.

Secondary Polycythemia

Secondary polycythemia occurs in response to hypoxia from insufficient oxygen, such as at high altitudes or cardiac failure.
Red blood cell counts can rise to 6 to 7 million/mm³, approximately 30% above normal.
Physiologic polycythemia is commonly observed in people living at high altitudes (14,000 to 17,000 feet), facilitating high levels of physical exertion under low oxygen conditions.

Polycythemia Vera (Erythremia)

Polycythemia vera is characterized by red blood cell counts of 7 to 8 million/mm³ and hematocrit levels of 60 to 70%, compared to the normal 40 to 45%.
It results from genetic aberrations that cause uncontrolled red blood cell production, alongside excess white blood cells and platelets.
Increased hematocrit and total blood volume can lead to intense vascular engorgement, with potential for capillary blockage due to viscous blood.

Effects of Polycythemia on Circulation

Elevated blood viscosity slows peripheral blood flow, exacerbating venous return rates and contributing to hypertension.
Increased blood volume from polycythemia enhances venous return, creating complex hemodynamic interactions.

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Description

This quiz explores the mechanisms of iron transport and storage in the human body, focusing specifically on ferritin and transferrin. It covers how iron is mobilized when plasma levels are low and its significance for overall health.