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Renin Angiotensin Mechanism.

Disorders of Blood.

 Disorders of Blood.

Introduction:

  • Disorders of blood are broadly divided into,

    • Disorders of Erythrocytes.

    • Disorders of Leukocytes.

    • Disorders of Thrombocytes.

Disorders of Erythrocytes.

  • Disorders of red blood cells include,

    • Anaemias.

    • Hemolytic Diseases of the newborns.

Anaemia:

  • It is a clinical condition characterized by “Decreased Oxygen Carrying Capacity” of the blood.

  • The prime cause of this is gap between “RBC production and Haemolysis” i.e. “RBC production is slow as compared to RBC loss”.

Symptoms of Anaemia:

  1. Tachycardia.

  2. Palpitations.

  3. Breathlessness or fatigue.

Classification of Anaemias:

  • The classification of the anaemia is based on the cause, it is as follows,

    1. Impaired erythrocyte production.

      1. Iron deficiency 

      2. Megaloblastic anaemias 

      3. Hypoplastic anaemia.

    2. Increased erythrocyte loss.

      1. Haemolytic anaemias.

      2. Normocytic anaemia.

Iron Deficiency ANaemia:

  • Most common form.

  • Result from decrease in intake of dietary iron.

  • Common Causes:

    • Blood Loss due to surgery or accidents.

    • Menorrhagia.

    • Hemorrhoids.

    • etc.

  • Normal Iron Requirements:

    • Male: 1-2 mg.

    • Female: 3 mg.

  • The erythrocytes during this type of anaemia appear Microcytic and hypochromic due to leser Hb in them.

Megaloblastic anaemia:

  • Maturation of RBCs takes place under the influence of Vitamin B12 and folic acid.

  • Deficiency of these vitamins leads to formation of abnormally large erythrocytes (megaloblasts).

  • These megaloblasts are fragile and have a lesser life span of 15-30 days.

  • Their early destruction causes anaemia.

Pernicious anaemia:

  • Caused due to deficiency of Vitamin B12.

  • It occurs more often in females than males, usually between 45 and 65 years of age. 

  • It is an autoimmune disease in which auto-antibodies destroy intrinsic factor (IF) and parietal cells in the stomach.

Hypoplastic and Aplastic Anaemias:

  • Happens due to deficient functioning of the red bone marrow.

  • As red bone marrow also deals with production of wbcs and platelets also this condition leads to decreased number of all three types of blood cells the condition is called “Pancytopenia”.

  • It may be caused due to certain drugs like anticancer drugs, viral infections, acute nephritis etc.

Congenital haemolytic anaemias:

  • In these diseases genetic abnormality leads to the synthesis of abnormal haemoglobin and increased red cell membrane friability, reducing cell oxygen-carrying capacity and life span. 

  • The most common forms are Sickle cell anaemia and Thalassaemia.

  • Sickle cell anaemia:

    • Hb molecules are abnormal when combined with oxygen the RBCs are “Sickle Shaped”.

    • Life span of cells is reduced and friability increases due to the shape.

    • Although this condition leads to anaemia the individuals are resistant to malaria.

  • Thalassaemia:

    • There is reduced globin synthesis with resultant reduced haemoglobin production and increased friability of the cell membrane, leading to early haemolysis.

Haemolytic disease of the newborn:

  • In this disorder, the mother's immune system makes antibodies to the baby's red blood cells, causing haemolysis and phagocytosis of fetal erythrocytes. 

  • The antigen system involved is usually (but not always) the Rhesus (Rh) antigen.

  • This happens when Mother having Rh -ve blood conceives a child with Rh +ve blood.

  • During pregnancy the placenta prevents entry of fetal rbcs in the mothers circulation hence avoiding the complications.

  • During delivery the few fetal rbcs enter mothers circulation which produces antibodies against these fetal rbcs as they contain Rh antigen.

  • The formed antibodies against the Rh antigen can cross placenta and enter the fetal circulation causing hemolysis in foetus.

  • In some cases child birth is anaemic while in some severe cases it may cause death of the child inside the womb.

  • This can be prevented by giving Anti Rh antibody injection to mother before 72 hrs of delivery.

Polycythaemia:

  • Increased no. of RBCs is called polycythemia, it results in increased blood viscosity affecting the blood flow.

Leukocyte Disorders:

  1. Leukopenia:

  • Total blood leukocyte count goes below the normal levels i.e. is less than 4 x 109 /1 (4000/mm3 ).

  1. Leukocytosis:

  • Total blood leukocyte count goes above the normal levels i.e. is more than 11 x 109 /1 (11000/mm3 ).

  1. Leukemia:

  • Leukaemia is a malignant proliferation of white blood cell precursors by the bone marrow. 

  • It results in the uncontrolled increase in the production of leukocytes.

  • Commonly it is termed as blood cancer.

Thrombocyte Disorders:

  1. Thrombocytopenia:

  • This is defined as a low blood platelet count below i.e.  150 000/mm3  but becomes more severe when the count falls below 30 000/mm3. 

  • It is caused due to a reduced rate of platelet production or increased rate of destruction.

Commonly Asked Questions:

  1. Write a short note “Haemolytic disease of the newborn”.

  2. What is anaemia? Write in short about Sickle Cell Anaemia”.

  3. Discuss different blood disorders.

  4. Define,

    1. Pancytopenia.

    2. Leukemia.

    3. Thrombocytopenia.

    4. Anaemia. 
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