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Questions and Answers
What is a significant characteristic of mature red blood cells regarding organelles?
What is a significant characteristic of mature red blood cells regarding organelles?
- They have lost all organelles including cytoplasmic organelles. (correct)
- They maintain some organelles for metabolic functions.
- They have a high number of mitochondria for energy production.
- They contain a nucleus and numerous organelles.
What shape do mature red blood cells acquire to facilitate their function?
What shape do mature red blood cells acquire to facilitate their function?
- Cuboidal
- Biconcave (correct)
- Flattened
- Spherical
Which statement about the red blood cell membrane is correct?
Which statement about the red blood cell membrane is correct?
- It is impermeable to all substances.
- It is rigid to maintain cell shape.
- It contains a lipid bilayer and membrane skeleton protein lattice. (correct)
- It is composed entirely of carbohydrates.
What happens to the size and surface area of a cell when it increases in size?
What happens to the size and surface area of a cell when it increases in size?
Why do mature red blood cells undergo active endocytosis and exocytosis?
Why do mature red blood cells undergo active endocytosis and exocytosis?
Which statement correctly describes erythrokinetics?
Which statement correctly describes erythrokinetics?
What is the average diameter of mature red blood cells?
What is the average diameter of mature red blood cells?
What is the primary composition of the lipid bilayer in red blood cell membranes?
What is the primary composition of the lipid bilayer in red blood cell membranes?
What is the main function of the hexose monophosphate shunt in red blood cells?
What is the main function of the hexose monophosphate shunt in red blood cells?
What can the presence of Heinz bodies in red blood cells indicate?
What can the presence of Heinz bodies in red blood cells indicate?
What is G6PD and its significance in the oxidative pathway?
What is G6PD and its significance in the oxidative pathway?
Which pathway's activity increases with increased oxidation of glutathione?
Which pathway's activity increases with increased oxidation of glutathione?
How does reduced glutathione protect hemoglobin in red blood cells?
How does reduced glutathione protect hemoglobin in red blood cells?
What is a consequence of a defective hexose monophosphate shunt?
What is a consequence of a defective hexose monophosphate shunt?
Which staining method can be used to identify Heinz bodies?
Which staining method can be used to identify Heinz bodies?
What is the role of NADPH in red blood cells?
What is the role of NADPH in red blood cells?
Which condition is associated with elevated EPO levels due to an increase in RBC production?
Which condition is associated with elevated EPO levels due to an increase in RBC production?
What type of RBC destruction is characterized by fragmentation of the erythrocyte membrane?
What type of RBC destruction is characterized by fragmentation of the erythrocyte membrane?
What is the primary reason for increased EPO levels during hemorrhage?
What is the primary reason for increased EPO levels during hemorrhage?
Which condition typically leads to decreased levels of EPO?
Which condition typically leads to decreased levels of EPO?
In the context of erythropoiesis, what does the term 'erythron' refer to?
In the context of erythropoiesis, what does the term 'erythron' refer to?
What effect does anemia have on EPO levels?
What effect does anemia have on EPO levels?
Which of the following processes does NOT result in an increase of EPO levels?
Which of the following processes does NOT result in an increase of EPO levels?
What is a common consequence of increased RBC destruction in the body?
What is a common consequence of increased RBC destruction in the body?
What happens to haptoglobin when free hemoglobin is released into circulation?
What happens to haptoglobin when free hemoglobin is released into circulation?
Which type of hemolysis primarily involves the breakdown of red blood cells in the bloodstream?
Which type of hemolysis primarily involves the breakdown of red blood cells in the bloodstream?
What is one result in the urine when hemosiderin is present in significant quantities?
What is one result in the urine when hemosiderin is present in significant quantities?
Which substance is produced from methemoglobin after oxidation of free hemoglobin?
Which substance is produced from methemoglobin after oxidation of free hemoglobin?
What primary organ system is responsible for extravascular hemolysis?
What primary organ system is responsible for extravascular hemolysis?
Which of the following conditions is least likely to be associated with membrane defects in red blood cells?
Which of the following conditions is least likely to be associated with membrane defects in red blood cells?
What is formed when bilirubin is conjugated by hepatocytes?
What is formed when bilirubin is conjugated by hepatocytes?
What is indicated by the presence of hemosiderin in urine?
What is indicated by the presence of hemosiderin in urine?
What is the primary consequence of osmotic lysis in red blood cells?
What is the primary consequence of osmotic lysis in red blood cells?
Which cells are primarily involved in erythrophagocytosis?
Which cells are primarily involved in erythrophagocytosis?
Which mechanism of destruction is associated with antigen-antibody reaction?
Which mechanism of destruction is associated with antigen-antibody reaction?
What is the role of haptoglobin in the bloodstream?
What is the role of haptoglobin in the bloodstream?
What happens during hemoglobin denaturation?
What happens during hemoglobin denaturation?
What can occur as a result of complement induced cytolysis?
What can occur as a result of complement induced cytolysis?
What is hemoglobinuria a sign of?
What is hemoglobinuria a sign of?
What failure leads to hemoglobin denaturation and the formation of Heinz bodies?
What failure leads to hemoglobin denaturation and the formation of Heinz bodies?
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Study Notes
RBCÂ Membrane Characteristics
- Mature red blood cells (RBCs) are 6-8 microns in diameter, with an average of 7.5 microns.
- They have a biconcave shape.
- Mature RBCs lack a nucleus and organelles because of stopped mitosis during development.
- Mature RBCs have a flexible membrane that allows them to pass through capillaries.
RBC Structure
- The RBC membrane consists of a protein lattice and a lipid bilayer.
- The lipid bilayer is composed of approximately 40% lipids, mostly phospholipids and cholesterol.
- It also contains 8% carbohydrates, which are linked to lipids or proteins.
RBC Membrane Skeleton
- The membrane skeleton gives the RBC its biconcave shape and flexibility.
- It is constantly changing as the RBC moves through the circulation.
RBC Metabolic Pathways
- RBCs have a unique metabolic pathway known as the hexose monophosphate shunt (also known as the pentose phosphate pathway).
- The hexose monophosphate shunt uses glucose to produce NADPH, which reduces glutathione.
- Glutathione is essential for protecting hemoglobin from denaturation and oxidation.
- Heinz bodies are inclusion bodies found in RBCs that indicate denatured hemoglobin.
- Heinz bodies can be identified using crystal violet or supravital stains.
- The methemoglobin reductase pathway also helps protect hemoglobin from oxidation by converting methemoglobin back to hemoglobin.
Erythrokinetics
- Erythrokinetics refers to the dynamic process of RBC production (erythropoiesis) and destruction.
- The erythron comprises all stages of erythrocytes, including developing precursors in the bone marrow and circulating RBCs in peripheral blood.
- Increased EPO levels signify erythroid hyperplasia, polycythemia, hemorrhages, and increased RBC destruction.
- Decreased EPO levels indicate anemia.
###Â Mechanism of Red Cell Destruction
- RBC destruction can occur intravascularly (within the circulation) or extravascularly (outside the circulation).
- Intravascular hemolysis involves the lysis of RBCs within the circulation.
- Extravascular hemolysis occurs in the reticuloendothelial system (RES) of the liver and spleen.
Intravascular Hemolysis
- Intravascular hemolysis usually occurs due to complement sensitization of RBCs.
- It accounts for 10% of aged RBC destruction.
- It involves the breakdown of hemoglobin within the blood circulation, leading to the release of free hemoglobin into plasma.
- Free hemoglobin binds to haptoglobin, which then transfers it to the liver for processing.
- Some free hemoglobin is taken up by renal tubular cells, producing hemosiderin crystals.
- Hemoglobin in plasma is called hemoglobinemia, while hemoglobin in urine is called hemoglobinuria.
Extravascular Hemolysis
- Extravascular hemolysis is the most common type of RBC destruction, accounting for around 90% of aged RBC destruction.
- It involves the phagocytosis of aged RBCs by macrophages in the spleen, liver, and bone marrow.
- It is often triggered by membrane defects, such as deficiencies in lipids, carbohydrates, or proteins.
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