RBC YR1..pptx introduction to red blood.

blood, fluid that transports oxygen and nutrients to the cells and carries away carbon dioxide and other waste products. Technically, blood is a transport liquid pumped by the heart (or an equivalent structure) to all parts of the body, after which it is returned to the heart to repeat the process. Blood is both a tissue and a fluid. It is a tissue because it is a collection of similar specialized cells that serve particular functions. These cells are suspended in a liquid matrix (plasma), which makes the blood a fluid. If blood flow ceases, death will occur within minutes because of the effects of an unfavourable environment on highly susceptible cells.

1. FACULTY OF LABORATORY MEDICINE AND DIAGNOSIS Topic: INTRODUCTION TO BLOOD. DR JABBA. 5/25/2024 FACULTY of Laboratory Medicine and Diagnostics 1

2. RED BLOOD CORPUSCLES(ERYTHROCYTES/RBC’S). The red blood corpuscles are the main constituents of the blood. They are not true cells because they have no nuclei so they are called corpuscles . The average number of erythrocytes is 5.5 million/mm3 in males and 4.8 million/mm3 in females . The count varies with age being high in newly born infants and less in growing children and old age. People living at high altitudes and athletes have a higher erythrocyte count.

3. CHARACTERISTICS OF ERYTHROCYTES. SHAPE AND SIZE. Erythrocytes are circular, biconcave, non nucleated discs, about 7.2micrometer in diameter and 2.2micrometer in thickness with a volume of 90 cubic micro. They contain the red respiratory pigment called hemoglobin Erythrocytes lack many of the normal cellular components such as: Mitochondria and ribosomes because of their highly specialized function in oxygen transport.

4. VARIATION IN SIZE AND SHAPE OF RBC. Variation in size is called Anisocytosis : Microcytosis , i.e. decrease in the size of RBCs occurs: – In iron deficiency anemia, – During prolonged forced breathing and – When osmotic pressure of the blood is increased. Macrocytosis , i.e. increase in the size of RBCs occur: – In megaloblastic anemia, – During muscular exercise and – When osmotic pressure of the blood is decreased.

5. VARIATION IN SHAPE OF RBC. Variation in shape is called poikilocytosis . Abnormal shapes of the RBCs are given below: Spherocyte Elliptocytes Sickle cell Poikilocytes

6. PHYSIOLOGICAL VARIATION IN RBC COUNTS . Physiological increase in the RBC count (physiological polycythaemia ) is seen in the following circumstances: Age : At birth, the RBC count is 6−7 million/ μL of blood. After about 10 days of birth the count decreases due to the destruction of cells. This is the cause of physiological jaundice of newborn. In infants, the RBC count is slightly more than the adults. Sex : RBC count in the adult females (average 4.8 million/ μL ) is lower than the adult males (average 5.5 million/ μL ). High altitude : Individuals residing in high altitude areas (above 10,000 feet from the sea level) have high RBC count (7 million/ μL ) because of the hypoxic stimulation of erythropoiesis. Excessive exercise : Mild hypoxia and spleen contraction causes temporary increase in the RBC count. Emotional conditions like anxiety are associated with the temporary increase in the RBC count due to sympathetic stimulation. After meals , the RBC count is raised slightly.

7. POLYCYTHEMIA. Polycythaemia refers to a pathological increase in the RBC count (above 7 million/ μL ) is of two types: Primary polycythaemia or polycythaemia vera : occurs in myeloproliferative disorder like malignancies of the bone marrow. The RBC count is persistently above 14 million/ μL and is always associated with high white blood cell (WBC) count. Secondary polycythaemia : occurs due to certain conditions producing a state of chronic hypoxia in the body such as: – congenital heart disease and – chronic respiratory disorders like emphysema.

8. PHYSIOLOGICAL DECREASE IN RBC COUNT. Physiological decrease in RBC count is seen in the following conditions: At high barometric pressure. After sleep and. In pregnancy.

9. COMPOSITION OF RBC. The body of the RBC bounded by the cell membrane contains a sponge-like stroma which is composed of the following structures: Water: constitutes 60% of the wet weight of the RBC. Hemoglobin ( Hb): held in the meshes of stroma, constitutes 35% of the wet weight and 90% of the dry weight of the RBC. Lipids: form the major constituents of the rest of 5% of stroma. These include cephalin, lecithin and cholesterol

10. CONTINUES…………… Proteins: include glutathiones and an albumin-like insoluble protein. These act as reducing agents preventing damage to the Hb. Lipoproteins: Almost half of the lipids are bounded to the protein forming a lipoprotein complex known as elenin (Calvin). Enzymes of the glycolytic system, catalase, carbonic anhydrase and other enzymes and inorganic salts are also present in the RBC

11. CONTINUES…….. Glucose and amino acids : are present in a small amount. Ions : Anions of the plasma (Cl–, PO4 3–, HCO3 –) are present often in large amounts. The cations Na+ and Ca2+ are either present in a very small amount or are absent. Cation K+ is present in a sufficient amount inside the RBC. Non-protein nitrogenous (NPN) substances: Urea, NH4, creatine and uric acid have a higher concentration inside the RBC than the plasma.

12. FORMATION OF RED BLOOD CELLS. Formation of RBCs is a part of the process of development of blood cells (RBCs, WBCs and platelets) called Hemopoiesis which includes: Erythropoiesis : This is the development of RBCs. Leucopoiesis : This is the development of WBCs . Thrombopoiesis or megakaryocytopoiesis : This is the development of platelets.

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