Erythrocytes

Question 1

What are the physical charecteristric of RBC?

Answer 1

1. Biconcave disc
2. Non-nucleate and lacks major organelles
3. Average diameter: 7.8 micrometre
4. Average thicness: 2.5 micrometre (thickest); 1 micrometre (thinnest)
5. Average volume: 90 -95 cubic micrometre

Question 2

What are the advantages of having a biconcave disc shaped RBC?

Answer 2

1. Provides flexibility to fold in the capillary
2. Increases surface area for diffusion and decreases distance of diffusion.
3. 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

Question 3

What is the membrane skeleton of an RBC made of?

Answer 3

The membrane of RBC contains spectrin which is anchored to transmembrane proteins Band 3 through ankyrin.

Question 4

What is band 3?

Answer 4

Band 3 are transmembrane proteins of erythrocytes. They are also important for anion exchange.

Question 5

What is the RBC count in men and women?

Answer 5

Men: 5 million - 6 million cells per cubic millimetre
Women: 4 million -5 million cells per cubic millimetre

Question 6

What happens when there are too few RBCs in the blood?

Answer 6

1. Tissue Hypoxia: Due to decreased oxygen transport to cells
2. Palpitations: Caused by decreased resistance in blood flow that increased workload on the heart.

Question 7

What happens when there are too many RBCs?

Answer 7

1. Increase in blood viscosity.
2. Blue colouration caused by increase in the amount of deoxygenated RBCs

Question 8

How does the body respond in the case of two few RBCs in the blood?

Answer 8

Low RBC blood count is first detected in the kidneys, making them the “first responders”.
Kidneys increase production of eryhtropoeitin to increase RBC production.

Question 9

What is the RBC composed of?

Answer 9

1. 97% Hb
2. Carbonic anhydrase: an enzyme that catalyses the reversible reaction between the CO2 and H2O to form carbonic acid (H2CO3)

Question 10

What is the function of Hb?

Answer 10

1. Transfer of gases
2. Excellent blood buffer

Question 11

Why is RBC a good gas transporter?

Answer 11

1. It is small and biconcave in shape which gives it high surface area for diffusion of gases.
2. It has 97% Hb.
3. RBC gets energy through anaerobic pathway. Since, it has no mitochondria, it does not use any of the oxygen it transports.

Question 12

What is the Hb count in men and women?

Answer 12

Men: 15g/ 100mL
Women: 14g/ 100mL

Question 13

What is the lifespan of RBCs in the blood?

Answer 13

60-120 days

Question 14

What characterises an old RBC?

Answer 14

1. Fragile and rigid
2. The Hb inside begins to degenerate

Question 15

How do the RBCs die in the body?

Answer 15

RBCs are engulfed by macrophages and lysed in the reticuloendothelial system.

The RE system consists of the bone marrow, live and spleen.

Question 16

How is Hb metabolised in the body?

Answer 16

1. Globin is metabolised to give amino acids.
2. 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).

Question 17

What is the role of spleen in the fate of RBCs?

Answer 17

1. Spleen filters aged and abnormal RBCs.
2. Site of Extramedullary Hemopoiesis: Produces RBCs when required along with lymphocytes, plasma cells and antibodies.

Question 18

What is hematocrit?

Answer 18

(Total volume of RBCs/ Total volume of blood) * 100

Question 19

What is MCV?

*Mean Corpuscular Volume

Answer 19

It is the average volume of one blood cell.
(PCV/ RBC count in millions) * 10

Question 20

What are normocytes, microcytes and macrocytes?

Answer 20

Normocytes: MCV 75-100 fL
Microcytes: MCV < 75 fL
Macrocytes: MCV > 100 fL

Question 21

What is MCH?

*Mean Corpuscular Hemoglobin

Answer 21

It is the average amount of Hb per RBC.
(Hb/RBC count in millions) * 10

Question 22

What are normochromic, hypochromic and hyperchromic RBCs?

Answer 22

Normochromic: MCH 26-34 pg
Hypochromic: MCH < 26 pg
Hyperchromic: MCH > 34 pg

Question 23

What is MCHC?

*Mean Corpuscular Hemoglobin Concentration

Answer 23

It is the volume of Hb per 100 mL of RBCs.
(Hb/ PCV) * 100

Question 24

What is the normal range of MCHC?

Answer 24

33- 35%