Erythrocytes Flashcards
What are the physical charecteristric of RBC?
- Biconcave disc
- Non-nucleate and lacks major organelles
- Average diameter: 7.8 micrometre
- Average thicness: 2.5 micrometre (thickest); 1 micrometre (thinnest)
- Average volume: 90 -95 cubic micrometre
What are the advantages of having a biconcave disc shaped RBC?
- Provides flexibility to fold in the capillary
- Increases surface area for diffusion and decreases distance of diffusion.
- Variations in RBC shape and dimensions are useful in differential diagnosis of anemias
Biconcave shape gives the RBC 30% more surface area than spherical shape
What is the membrane skeleton of an RBC made of?
The membrane of RBC contains spectrin which is anchored to transmembrane proteins Band 3 through ankyrin.
What is band 3?
Band 3 are transmembrane proteins of erythrocytes. They are also important for anion exchange.
What is the RBC count in men and women?
Men: 5 million - 6 million cells per cubic millimetre
Women: 4 million -5 million cells per cubic millimetre
What happens when there are too few RBCs in the blood?
- Tissue Hypoxia: Due to decreased oxygen transport to cells
- Palpitations: Caused by decreased resistance in blood flow that increased workload on the heart.
What happens when there are too many RBCs?
- Increase in blood viscosity.
- Blue colouration caused by increase in the amount of deoxygenated RBCs
How does the body respond in the case of two few RBCs in the blood?
Low RBC blood count is first detected in the kidneys, making them the “first responders”.
Kidneys increase production of eryhtropoeitin to increase RBC production.
What is the RBC composed of?
- 97% Hb
- Carbonic anhydrase: an enzyme that catalyses the reversible reaction between the CO2 and H2O to form carbonic acid (H2CO3)
What is the function of Hb?
- Transfer of gases
- Excellent blood buffer
Why is RBC a good gas transporter?
- It is small and biconcave in shape which gives it high surface area for diffusion of gases.
- It has 97% Hb.
- RBC gets energy through anaerobic pathway. Since, it has no mitochondria, it does not use any of the oxygen it transports.
What is the Hb count in men and women?
Men: 15g/ 100mL
Women: 14g/ 100mL
What is the lifespan of RBCs in the blood?
60-120 days
What characterises an old RBC?
- Fragile and rigid
- The Hb inside begins to degenerate
How do the RBCs die in the body?
RBCs are engulfed by macrophages and lysed in the reticuloendothelial system.
The RE system consists of the bone marrow, live and spleen.
How is Hb metabolised in the body?
- Globin is metabolised to give amino acids.
- Heme group is meabolised in the liver to give iron and bilirubin. Iron is stored as ferritin and hemosiderin.
Bilirubin is released in the intestines as bile-> urobilogen-> stercobilin (by bacteria and released in the feces).
What is the role of spleen in the fate of RBCs?
- Spleen filters aged and abnormal RBCs.
- Site of Extramedullary Hemopoiesis: Produces RBCs when required along with lymphocytes, plasma cells and antibodies.
What is hematocrit?
(Total volume of RBCs/ Total volume of blood) * 100
What is MCV?
*Mean Corpuscular Volume
It is the average volume of one blood cell.
(PCV/ RBC count in millions) * 10
What are normocytes, microcytes and macrocytes?
Normocytes: MCV 75-100 fL
Microcytes: MCV < 75 fL
Macrocytes: MCV > 100 fL
What is MCH?
*Mean Corpuscular Hemoglobin
It is the average amount of Hb per RBC.
(Hb/RBC count in millions) * 10
What are normochromic, hypochromic and hyperchromic RBCs?
Normochromic: MCH 26-34 pg
Hypochromic: MCH < 26 pg
Hyperchromic: MCH > 34 pg
What is MCHC?
*Mean Corpuscular Hemoglobin Concentration
It is the volume of Hb per 100 mL of RBCs.
(Hb/ PCV) * 100
What is the normal range of MCHC?
33- 35%
