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Questions and Answers
What is the function of red blood cells (erythrocytes) in the body?
What is the function of red blood cells (erythrocytes) in the body?
- Serve as an excellent acid-base buffer
- Contain carbonic anhydrase, which catalyzes the reaction: CO2 + H2O H2CO3
- Carry hemoglobin and bear CO2 to the tissues
- Transport O2 to the tissues (correct)
What is the shape of red blood cells?
What is the shape of red blood cells?
- Cuboidal
- Biconcave discs (correct)
- Spherical
- Irregular polygons
What is the average volume of red blood cells?
What is the average volume of red blood cells?
- 50-60 micrometers3
- 90-95 micrometers3 (correct)
- 70-80 micrometers3
- 100-110 micrometers3
At higher altitudes, what happens to red blood cell counts?
At higher altitudes, what happens to red blood cell counts?
Which parameter indicates the mean cell volume of red blood cells?
Which parameter indicates the mean cell volume of red blood cells?
What does MCHC stand for and represent in terms of red blood cells?
What does MCHC stand for and represent in terms of red blood cells?
Which nutrient is present in green vegetables, some fruits, and meats?
Which nutrient is present in green vegetables, some fruits, and meats?
What can lead to a deficiency of folic acid?
What can lead to a deficiency of folic acid?
What might maturation failure indicate according to the text?
What might maturation failure indicate according to the text?
Which stage of RBC formation retains a small amount of endoplasmic reticulum and mRNA?
Which stage of RBC formation retains a small amount of endoplasmic reticulum and mRNA?
What is the predominant form of hemoglobin in adults?
What is the predominant form of hemoglobin in adults?
How many oxygen atoms can each hemoglobin molecule transport?
How many oxygen atoms can each hemoglobin molecule transport?
What is the role of erythropoietin in RBC production?
What is the role of erythropoietin in RBC production?
Why is vitamin B12 important for cell proliferation?
Why is vitamin B12 important for cell proliferation?
What is a consequence of abnormal DNA replication due to lack of vitamin B12?
What is a consequence of abnormal DNA replication due to lack of vitamin B12?
How does intrinsic factor help in vitamin B12 absorption?
How does intrinsic factor help in vitamin B12 absorption?
What is the usual duration for which normal stores of vitamin B12 are adequate?
What is the usual duration for which normal stores of vitamin B12 are adequate?
How does erythropoietin level change once tissue oxygenation is restored?
How does erythropoietin level change once tissue oxygenation is restored?
What is the main reason for regulating red blood cell mass within a narrow range?
What is the main reason for regulating red blood cell mass within a narrow range?
In what condition may extramedullary hematopoiesis occur?
In what condition may extramedullary hematopoiesis occur?
What can result in red cell mass above the normal range?
What can result in red cell mass above the normal range?
What stimulates Erythropoietin (EPO) production in response to hypoxia?
What stimulates Erythropoietin (EPO) production in response to hypoxia?
Where is approximately 90% of Erythropoietin (EPO) made in the body?
Where is approximately 90% of Erythropoietin (EPO) made in the body?
In anephric individuals, where does the 10% residual EPO mainly come from?
In anephric individuals, where does the 10% residual EPO mainly come from?
What happens to hemoglobin released from senescent RBCs?
What happens to hemoglobin released from senescent RBCs?
Which organ secretes apotransferrin into the bile?
Which organ secretes apotransferrin into the bile?
What is the function of transferrin in the body?
What is the function of transferrin in the body?
What happens to RBCs as enzymes deplete with age?
What happens to RBCs as enzymes deplete with age?
How is iron absorbed in the body?
How is iron absorbed in the body?
What is the daily iron loss in men and women, respectively?
What is the daily iron loss in men and women, respectively?
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Study Notes
Folic Acid Deficiency
- Folic acid is present in green vegetables, fruits, and meats.
- Destroyed during cooking, and subject to dietary deficiencies.
- Deficiencies may occur in cases of intestinal malabsorption.
- Maturation failure may reflect combined B12 and folate deficiency.
Hemoglobin Formation
- Occurs from proerythroblast through reticulocyte stage.
- Reticulocytes retain a small amount of endoplasmic reticulum and mRNA, supporting continued hemoglobin synthesis.
Hemoglobin Structure
- Consists of four subunits: α, β, γ, δ.
- Each globin chain is associated with one heme group containing one atom of iron.
- Each hemoglobin molecule can transport 8 oxygen atoms.
Response to Hypoxia
- Erythropoietin production increases within minutes to hours.
- New circulating reticulocytes appear in ~3 days.
- Erythropoietin drives production of proerythroblasts from HSCs and accelerates their maturation into RBCs.
- Can increase RBC production up to 10-fold.
Vitamin B12 and Folic Acid
- Required for DNA replication and cell proliferation.
- Abnormal DNA replication causes failure of nuclear maturation and cell division, leading to fragile "macrocytes".
Pernicious Anemia
- Failure to absorb vitamin B12 due to atrophic gastric mucosa and lack of intrinsic factor.
- Vitamin B12 is stored in the liver and released as needed.
Red Blood Cells (Erythrocytes)
- Carry hemoglobin, bearing oxygen to the tissues.
- Contain carbonic anhydrase, which catalyzes the reaction: CO2 + H2O → H2CO3.
- Hemoglobin is an excellent acid-base buffer.
RBC Size and Shape
- Biconcave discs with a mean size of 7.8 x 2.5 microns (thickest) or x 1 micron (center).
- Average volume is 90-95 micrometers3.
RBC Count and Indices
- Men: 5,200,000 (± 300,000) / mm3.
- Women: 4,700,000 (± 300,000) / mm3.
- RBC indices: MCV, MCH, MCHC, and RDW.
Regulation of Red Cell Mass
- Red blood cell mass is regulated to maintain adequate oxygen carrying capacity and avoid excessive blood viscosity.
Tissue O2 and Erythropoietin
- Hypoxia stimulates erythropoietin production, leading to increased RBC production.
Erythropoietin (EPO)
- Circulating hormone necessary for erythropoiesis in response to hypoxia.
- 90% produced in the kidneys, with some production in the liver.
Iron Balance
- Daily iron loss: 0.6 mg/day in men, 1.3 mg/day in women.
- Iron is absorbed throughout the small intestine, stored in the liver, and transported by transferrin.
RBC Senescence & Destruction
- RBC life span is ~120 days.
- As enzymes deplete with age, RBCs become fragile and rupture in small passages, often in the spleen.
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