Chapter 8: The Blood PDF

# Chapter 8: The Blood ## Introduction Blood is specialized fluid connective tissue that circulates in blood vessels. Blood accounts for about 7% of the total human body weight. - **Hematology**: Branch of medical science that deals with the study of blood and related disorders. ## Physical Chara...

# Chapter 8: The Blood ## Introduction Blood is specialized fluid connective tissue that circulates in blood vessels. Blood accounts for about 7% of the total human body weight. - **Hematology**: Branch of medical science that deals with the study of blood and related disorders. ## Physical Characters of Blood - Blood is red, opaque, viscous and slightly alkaline in nature. - pH of blood is 7.35 – 7.45. - Specific gravity is 1.055 – 1.060. - Volume – 5-6 Liters (Male) 4-5 Liters (Female). ## Functions of Blood Blood performs the following important functions: 1. **Transport of Gases**: Blood transports gases (O2, CO₂ etc.) from lungs to cells & from cells to tissues. 2. **Transport of Nutrients**: Blood transports nutrients to body cells and tissues. 3. It helps in regulation of pH. 4. It regulates body temperature and water balance. 5. It helps in prevention of hemorrhage. 6. It helps in body defence. 7. Excretion of waste products. 8. Maintains acid-base balance. 9. Regulation of blood pressure. ## Composition of Blood Blood is composed of 55% plasma and 45% blood cell components. ### Plasma Plasma is a straw colored fluid that is composed of: - **Water**: 91-92% - **Solids**: 8-10% - **Organic Substances** - **Plasma proteins:** Albumin, Globulins, Fibrinogen, Prothrombin - **Nutrients:** Glucose, fatty acids, cholesterol, etc. - **Hormones** - **Enzymes** - **Gases:** O2, CO2, Nitrogen - **Waste products:** Urea, uric acids, creatinine etc. - **Inorganic substances:** Sodium salts, potassium, calcium, magnesium etc. ### Plasma Protein Makes up 7% of the total plasma: 1. **Albumin:** The most abundant plasma protein. Its main function is to maintain normal osmotic pressure. It is produced in the liver. 2. **Globulin:** It is formed in the liver and lymphoid tissue. Its main function is immune functions. 3. **Fibrinogen:** It is synthesized in the liver and plays an active role in blood clotting and the viscosity of blood. 4. **Prothrombin:** It is a precursor of thrombin. It is formed in the liver. Its main function is blood clotting and the maintenance of osmotic pressure. ## Cellular Components There are three types of blood cells or cellular components: ### 1. Red Blood Cells or Erythrocytes - Erythrocytes come from the word “Erythro” which means 'Red'. - The RBC is circular, disc-shaped, biconcave and non-nucleated. - It forms 98% of the blood cells. - Normal RBC is 7.2-8 um in diameter and 2.2 um in thickness. #### Erythropoiesis or Hematopoiesis: - The process of blood cell formation is called Erythropoiesis or Hematopoiesis. - During the embryonic period blood cells are formed in the yolk sac, liver, spleen, and lymphoid tissues. - In adults, red bone marrow produces blood cells. - Hemocytoblasts (stem cell) of red bone marrow form the blood cells. #### Composition: - It consists of 60-70% water, hemoglobin, phospholipids, and some organic or inorganic substances. #### Normal Counts: - 5-5.5 Million/mm³ in adult man. - 4.5-5 million/mm³ in adult woman. - 6-7 million/mm³ in infants. #### Functions: - Transportation of gases - Acid-base balance - Maintains viscosity of blood - Ionic balance #### Fate of RBC: - After 120 days, the RBC is destroyed by WBC in the spleen. Hb is broken into heme and protein. - Iron is stored for reuse and protein globulin chains are broken down to bilirubin, which causes yellow-colored urine and feces. - Remaining part of heme is called biliverdin. ### 2. White Blood Cells or Leukocytes - WBC are nucleated cells and do not contain hemoglobin. - They are produced in bone marrow. - Normal Values: 4000-11000/mm³ - Types: Two types - **Granular WBC:** Have granules present in their cytoplasm. - **Neutrophils:** First to respond to infection. They account for 60-70% of the WBC. - **Eosinophils:** Two lobed nuclei, Red granules. They develop in asthma, allergy reactions, etc. - **Basophils:** Blue granules that develop in allergic reactions. - **Agranular WBC:** Do not have granules in their cytoplasm. - **Lymphocytes:** Small cells with round nuclei. B-Lymphocytes mature in bone marrow and T-Lymphocytes develop in the thymus gland. B-Lymphocytes produce antibodies. - **Monocytes:** The largest of all leukocytes. Monocytes play an important role in immune defense and inflammation. #### Function of WBC: - WBC play an important role in first line defense. - Phagocytosis processes are completed with the help of WBC. - Their general function is to combat inflammation and infection. ### 3. Platelets or Thrombocytes - Platelets are the smallest oval-shaped cells that can only be seen under a microscope. They have no nucleus. - Normal Count: 1.50,000-4,50,000/mm² #### Origin: Platelets are produced by megakaryocytes of bone marrow. #### Function: - Platelets help in blood clotting. - Platelets release serotonin and histamine, which have hemostatic effects. - Platelets repair ruptured capillaries by adhering at the site. #### Factors involved in Coagulation: | Factor | Name | |---|---| | I | Fibrinogen | | II | Prothrombin | | III | Thromboplastin | | IV | Calcium ions | | V | Proaccelerin (Labile factor) | | VI | Absent | | VII | Proconvertin (Stable factor) | | VIII | Antihaemophilic factor | | IX | Plasma Thromboplastin Components (PTC), Christman factor | | X | Stuart Factor | | XI | Plasma Thromboplastin Antecedent | | XII | Hageman Factor | | XIII | Fibrin Stabilizing Factor | #### Coagulation or Clotting of Blood: - Blood coagulation is the process by which blood loss is prevented. - Platelets play an important role in the clotting of blood mechanism. - It usually takes 3-7 minutes, but the average coagulation time is 5 minutes. #### Mechanism of Blood Clotting: The mechanism of blood clotting consists of 3 mechanisms and 13 factors: 1. **Vasospasm:** After rupturing blood vessels, nerve reflex activates, causing the release of serotonin, which constricts blood vessels and reduces blood flow. 2. **Platelet Plug Formation:** Also known as the platelet phase. In this phase, the adhesion of platelets occurs. Platelets stick to each other and release granules containing ADP, which causes continued platelet plug formation. 3. **Formation of Clot:** Clot formation is a complex process, starting with two pathways. - **Extrinsic Pathway:** Tissue Injury - **Tissue factor** - **VII** - **X** - **V** - **Ca** - **Prothrombin activator** - **Intrinsic Pathway** - **XII** - **XI** - **IX** - **VIII** - **Ca** - **X** - **V** - **Ca** - **Tissue phospholipid** - **Prothrombin activator** There are 13 blood clotting or coagulation factors found in the blood. They are presented in Roman numerals (I-XIII) and are blood clotting proteins manufactured by the liver. These factors are responsible for the formation of the blood clot. ## Blood Group - **Karl Landsteiner** discovered blood groups. - Blood groups or blood types are classified on the basis of the presence and absence of inherited substances on RBC surfaces. - The most important blood group systems are the ABO and Rh systems. ### ABO System: The ABO system consists of 4 different blood groups (A, B, AB, and O). These are determined by the presence and absence of two antigens (A and B) on the surface of RBCs. 1. **Blood Group A:** It has A antigen (agglutinogen) on red cells and B antibody (agglutinin) in plasma. 2. **Blood Group B:** It has B antigen on red cells and A antibody in plasma. 3. **Blood Group AB:** It has A and B antigens on red cells and no antibody. 4. **Blood Group O:** It has no antigen on red cells and A and B antibodies in plasma. - **Blood group 'AB'** is called the "Universal Recipient" because their blood group contains no agglutinin, so they can receive blood from all blood groups. - **Blood group 'O'** is called the "Universal Donor" because their blood group contains no agglutinogen, so they can give to anyone in an emergency. ### Rh System: - The Rh system or Rhesus factor was first discovered in the Rhesus monkey. - There are six agglutinogens in the Rh system, but only the D agglutinogen is well described. - People who possess the D antigen are called (Rh+ve), and those who do not possess it are called (Rh-ve). ### ABO Incompatibility: - If blood group B receives blood from blood group A or AB, an incompatibility will occur. This occurs because the B antigens in red blood cells create anti-A antibodies in the plasma. These antibodies can destroy the A antigens in the plasma. ### Rh Incompatibility: - When an Rh-negative individual is transfused with Rh-positive blood, they will develop anti-Rh agglutinins. A reaction will not occur during the first transfusion, but if a second process occurs, a harmful reaction can happen. ### Clinical Notes: ### DISORDER OF Hb AND RBC 1. **Haemolysis:** Destruction of RBC, which liberates Hb in the cytosol of the cell. 2. **Polycythemia:** Elevated Red blood cell count due to a disorder of bone marrow. 3. **Anemia:** A decrease in the amount of RBC, Hb, or oxygen capacity of the blood, characterized by breathlessness, paleness, weakness, loss of appetite, etc. Some types of anemia: - **Iron deficiency anemia:** Most common type of anemia, where the rate of iron use is more than the rate of absorption. - **Aplastic anemia:** A rare type of anemia that occurs due to failure of bone marrow function. - **Haemolytic anemia:** Due to an increase in red blood cell destruction. - **Vit-B deficiency anemia:** Occurs as a result of vit-B12 or folic acid deficiency. ### DISORDER OF WBC: 1. **Leukocytosis:** An increase in the number of WBC beyond 11,000/mm3. 2. **Neutrophilia:** An increase in the number of neutrophils, usually found in acute infections, physical exercise, and pregnancy. 3. **Basophilia:** An increase in the number of basophils, usually found in allergic conditions and infections. 4. **Eosinophilia:** An increase in the number of eosinophils, usually found in asthma, allergic conditions, and other infections. 5. **Leukemia:** A type of blood cancer characterized by an increase in the number of WBC more than 80,000-100000/cm3. The most common types are acute-chronic myeloid and lymphocytic leukemia. 6. **Leukopenia:** A decrease in the number of white blood cells below 4,000/cm3, caused by various infections (Pneumonia, typhoid, etc.) drugs, and bone marrow disorders. ### DISORDER OF PLATELETS & CLOTTING 1. **Thrombocytosis**: A disease in which the platelets counts are decreased. Characterized by bleeding in the mouth and gums, petcheal hemorrhage (pinpoint blood spot). 2. **Thrombosis:** Formation of a blood clot in a blood vessel, which obstructs or slows down blood circulation, leading to death. 3. **Haemophilia:** A hereditary disorder caused by a deficiency of blood clotting factor VIII (antihaemophilic factor) that affects the blood's ability to clot. Women are carriers of this disease.