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Lec 4. 23 Octob.2017

Pro.Dr.baybeen Alselevany
Disorders of RBC
Objectives
I.-Abnormal variations in the structure of Hb
II.Anemia
III.polythycemia

I-Abnormal variations in the structure of Hb: Abnormalities may be either in the heme or the globin structure, but most frequently they are due to changes in the amino acid sequences of globin chains. There are two major types of inherited disorders of Hb in humans:
A: hemoglobinopathies: in which abnormal polypeptide chains are produced for example hemoglobin S (Hbs) found in sickle cell anemia. In Hbs, the α – chains are normal but the sixth amino acid of each β – chain has been changed from glutamic acid to valine (i.e. among the 146 amino acid residues in each β – chain, one glutamic acid residue has been replaced by a valine residue).

Hemoglobin

Position on β polypeptide chain of Hb

1 2 3 4 5 * 6 --------------------- 146

HbA (normal)

HbS(sickle cell)

Glutamic acid


Valine
The erythrocyte contains an abnormal type of Hb called HbS. When this Hb is exposed to hypoxia, it precipitates into long crystals inside the erythrocyte which give it the appearance of being a sickle rather than a biconcave disc.

B. Thalassemia: in which the chains are normal in structure but produced in decreased amounts or absent structure but produced in decreased amounts or absent because of defects in the regulatory portion of the globin genes i.e. thalassemia is due to abnormalities in globin synthesis.Thalassemias may be divided into two types according to the globin chain that is deficient.
1-α thalassemia: i.e. deficiency in the synthesis of α- polypeptide
chain.
2-β thalassemia: i.e. deficiency in the synthesis of β- polypeptide
chain.

II-The Anemia's

Anemia: means deficiency of hemoglobin in the blood which can be caused by either too few red blood cells or too little hemoglobin in the cells. The reduced Hb reduces the ability of the blood to transport O2. red blood cells or too little hemoglobin in the cells. Some types of anemia and their physiologic causes, are the following

II-The Anemias

Anemia means: 1. a deficiency in the total number of RBC’s (which are caused by either too rapid loss or too slow production of RBC’s) Or.2. Decrease in the amount (concentration) of Hb.The reduced Hb reduces the ability of the blood to transport O2.
.
Some types of anemia
1-Iron Deficiency Anemia (IDA).
The most common cause of impairment in Hb synthesis is the lack of iron. If the body lacks of iron, it cannot produce heme, and hence no Hb, resulting in a type of anemia known as iron deficiency anemia (IDA).IDA is by far the most common cause of all anemias .Causes of ID.
1. Blood loss: bleeding is by far the most common cause of IDA. Blood loss is usually in the form of a chronic hemorrhage caused by gastric or duodenal ulcers, excessive aspirin ingestion. In women of child bearing age, IDA is due to blood loss caused by menstruation, pregancy and child breath.
2. Malabsorption: partial or total gastrectomy may result in achlorhydria (no secretion of HCl) and as a result there is iron deficiency. Also tropical sprue inhibits iron absorption.
3. Poor diet: largely vegetables diet many produce iron deficiency.
2-Increased demand: three groups of people need increased amounts of iron. First: pregnant women. Second: infants and young children especially those that are breast or bottle-fed over a long period of time. Milk does not contain iron, and iron deficiency may develop unless supplemental iron is given. Third: older children and adolescents ned iron since they experiencing rapid growth.


Treatment of IDA:1- a course of treatment with oral iron e.g. ferrous suphate in the form of tablets.2-In the late pregnancy, parenteral iron is given by injection of iron.

2. Megaloblastic Anemia:

Megaloblastic anemia mean: the larger red blood cells in the circulation than normal blast cells or (megablastic) in the bone marrow.Cells are large with odd shapes.
Causes:1-Lack of folic acid in the diet. Lack of folic is the most common cause of megaloblastic anemia.2-Lack of vitamin B12. It is the second most cause of megaloblastic anemia. Vit B12 requires intrinsic factor for their absorption by small intestine.
Both vitamins folic acid & vit. B12 are essential for mature of RBC & synthesis of DNA. So lack of vit. B12 & folic acid can lead to slow reproduction of erythroblasts by bone marrow. Lack of vit. B12 lead to pernicious anemia which is an important form of megaloblastic anemia. Total gastrectomy can lead to pernicious anemia.

3-Aplastic Anemia: bone marrow aplasia means lack of functioning bone marrow i.e no blood cell production

4- Hemolytic Anemia:Hemolytic anemia: means an accelerated destruction of the peripheral RBC’s (i.e. accelerated hemolysis).RBC are fragile, rupture easily as they go through the capillaries, life span is short.
Types of hemolytic anemia: 1-Hereditary hemolytic anemia.e.g.sickle cell anemia. 2- Acquired hemolytic anemias. e.g. hemolytic disease of new born (HDN) which is also called erythroblastosis fetus. Causes of this disease:
1-Rh-incompatibility. 2- ABO incompatibility

effects of Anemia on Function of the Circulatory System

In severe anemia, the blood viscosity may fall.2 increased cardiac
output, as well as increased pumping workload on the heart.3. reduced oxygen-carrying capacity.

III-Polycythemia

Secondary Polycythemia. Whenever the tissues become hypoxic because of too little oxygen in the breathed air, such as at high altitudes, or because of failure of oxygen delivery to the tissues, such as in cardiac
failure, the blood-forming organs automatically produce large quantities of extra red blood cells. This condition is called secondary Polycythemia, and the red cell count commonly rises to 6 to 7 million/mm3, about 30 per cent above normal reasonably high levels of continuous work even in a rarefied atmosphere. A common type of secondary Polycythemia, called physiologic Polycythemia, occurs in natives who live at altitudes of 14,000 to 17,000 feet, where the atmospheric oxygen is very low.The blood count is generally 6 to 7 million/mm3; this allows these people to perform.
2.pathological condition known as Polycythemia Vera((erythremia), in which the red blood cell count may be 7 to 8
million/mm3 and the hematocrit may be 60 to 70 percent . Total blood volume also increases to almost twice normal and the viscosity of the blood in Polycythemia Vera sometimes increases from the normal of 3 times the viscosity of water to 10 times that of water.
.
Effect of Polycythemia on Function of the Circulatory System


1.greatly increased viscosity of the blood in Polycythemia .
2.The blue color of all this deoxygenated hemoglobin masks the red color of the oxygenated hemoglobin. Therefore, a person with Polycythemia vera ordinarily has a ruddy complexion with a bluish (cyanotic) tint to the skin.




رفعت المحاضرة من قبل: Deaa Al-deen El-taee
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