Red Blood Cells

(Contributed by Shoaib Meran)

Red Blood Cells

Red blood cells or RBCs or Erythrocytes.

  • Shape:

The mature human erythrocyte is flattened, biconcave disc and does not possess nucleus & mitochondria. The edges are rounded and thicker than the centre or in other words the shape of RBC is like dumb-bell. Each RBC contains 280million haemoglobin. It has diameter of 7.76µ & thickness at the periphery is and in the centre is or less.

  • Life span

The life span of RBC’s is 120days.

2.5 million RBC’s are produced /sec.

Old RBC’s removed from blood by Phagocytic cells in liver, spleen, & bone marrow

Iron recycled back into hemoglobin production

RBC’s Level in body of Male & Female:

PersonsNumber of RBC’s
 

In young healthy man normally

Number of RBC’s varies

 

5.5 x 106 / cubic milli meter

4.5 – 6.5 x 106 / cubic milli meter

 

In young healthy woman normally

Number of RBC’s varies

 

4.8 x 106 / cubic milli meter

4 – 5.6. x 106 / cubic milli meter

Composition of RBC’s:

RBC’s are made up of three components with specific concentration which are as follows

61% water, 34% haemoglobin & 5% Stroma. Stroma is chiefly composed of proteins, phospho-lipids, cholesterol, cholesterol esters and neutral fats.

Production of RBC’s:

  • Hematopoiesis is formation of blood cells from stem cells in marrow (myeloid tissue) & lymphoid tissue.
  • Erythropoiesis is formation of RBCs and Stimulated by erythropoietin (EPO) from kidney.

Physiological Variations in the blood RBC’s:

Physiological variation is due to following reasons

Diurnal:

The count is less during sleep.  Then gradually rises during the day and it is maximum in the Evening.

Exercise:

The RBC count increases with exercise.

Altitude:

At high altitudes the number rises and at low altitude the count falls.

Temperature:

High external temperature also raises the number of RBCs.

Adrenaline:

An injection of adrenaline raises the count of RBCs.

Oxygen:

Lower oxygen tension of arterial blood increases the red blood cell count.

Excitement:

Excitement also increases the RBC count.

By RBC’s destruction:

By RBC’s destruction following diseased conditions are occurred.

Erythrocytosis:

Condition in which increase in RBC count is due to some known stimulus, e.g. hypoxia etc

Polycythemia Vera:

In neoplastic disease, the bone-marrow very overactive and produces alarmingly high number of RBC. It is also called erythremia.

Anemia:

Anemia occurs due to deficiency of hemoglobin in the blood. Following types of anemia may occur;

  1. Blood Loss Anemia:

It is due to frequent blood loss by haemorrhage. In chronic blood loss a person cannot receive enough iron for the RBC’s production, so in the result small size RBC’s with too little haemoglobin inside them. This condition is known as microcytic hypochromic anemia (MHA).

  1. Aplastic Anemia:

Aplastic anemia occur when a person lack of functioning bone marrow. Gamma rays & excessive X-rays can completely destroy the bone marrow.

  1. Megaloblastic Anemia:

Vitamin B12, folic acid & intrinsic factor from the stomach mucosa are the components in which any one loss may lead to the slow production of RBC’s & results in Large size RBC’s production which are known as Megaloblasts.

  1. Hemolytic Anemia:

It is of different types which are as follows;

  1. a. Hereditary spherocytosis:

In this condition RBC’s are very small & spherical. When these cells are passed through the splenic pulp & some other tight vascular beds, they are easily rapture even by slight compression.

  1. b. Sickle cell anemia:

In this type the RBC’s have abnormal haemoglobin which is known as haemoglobin S (containing faulty beta chain). When this haemoglobin exposed to low concentration of oxygen it participates to form the long crystal chain inside the RBC & give the elongated shape of RBC & this abnormal haemoglobin may also destroy the cell membrane. This is known as sickle cell anemia.

  1. c. Erythroblastosis fetalis:

This condition occurs when Rh-positive red blood cells in the fetus are attacked by antibodies from an Rh-negative mother. This leads to the destruction of Red cells.

Author:

Shoaib Meran, Batch-5, Pharmaceutics Department, Hajvery University, Lahore, Pakistan.

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