Blood & Lymphatic System Study Guide PDF

# Unit I: Introduction ## Blood Properties and Components (Physiology) ### Intended Learning Outcomes (ILOS): By the end of this topic the student should be able to: - Recognize properties and composition of the blood. - Identify the blood functions. - State the normal constituents of the plasma....

# Unit I: Introduction ## Blood Properties and Components (Physiology) ### Intended Learning Outcomes (ILOS): By the end of this topic the student should be able to: - Recognize properties and composition of the blood. - Identify the blood functions. - State the normal constituents of the plasma. - Differentiate between plasma and serum. - Interpret factors affecting albumin/ globulin ratio. - Describe the physiological functions of plasma proteins. ### Blood properties: - Blood is the red fluid contained in the blood vessels. - Blood represents about 8% of total body weight and has an average volume of 5 liters in woman and 5.5 liters in men. - The specific gravity: for whole blood is 1.060, for plasma 1.030 and for blood cells 1.090. - The viscosity of the whole blood is 5 times that of water, while viscosity of plasma is 2 times of water. ### Blood consists of: - **(a) Fluid part "plasma":** representing 55% of blood volume. - **(b) Cellular elements:** representing 45% of blood volume and three types of cells are present: - Red blood corpuscles "Erythrocytes" (RBCs) - White blood cells "Leukocytes" (WBCs) - Platelets "Thrombocytes". **Figure (1.1):** Cellular elements of blood: from left to right, human erythrocyte, thrombocyte, leukocyte. ### Functions of blood Blood maintains internal environment constant (i.e. Homeostasis) as regards water, pH, electrolytes concentration, temperature, etc. This is carried out through performing the following functions: - **A) Transport function:** - Blood carries O2 from the lungs to the tissues and CO2 from the tissues to the lungs to be expired (respiratory function). - Blood carries substances absorbed from the gastro-intestinal tract to the liver and the different tissues (nutritive function). - Blood transport non-volatile products of metabolism to the kidneys to be excreted (excretory function of waste products as urea and uric acid). - Blood transports hormones and other substances that regulate cell function to the target tissues. - **B) Regulation of body temperature:** - Plasma absorbs and distributes much of the heat produced during metabolic processes all over the body. - **C) Hemostatic function:** - Blood clots when a blood vessel is cut to close the injured part and thus prevents further loss of blood from the circulating system. - **D) Defensive function:** - White blood cells attack organisms that invade the body. - Antibodies are formed against invading organisms or foreign substances (immune mechanisms). - **E) Nutritive function:** - Blood provides a pool of nutrients for the tissues, there are free sugars, amino acids, fatty acids and minerals in the plasma and extra-amino acids can be obtained by breaking down the plasma proteins. ## PLASMA ### Plasma properties: - It is the fluid portion of blood. - Volume: 3.500 ml in a 70 Kg man (about 5% of body weight). - Color: Yellow. - Specific gravity: 1030. - pH: 7.4 - Viscosity: 2 times that of water. - Osmotic pressure: - Crystalloid OP= 5000mmHg. - Colloid OP (proteins) = 25 mmHg. ### Plasma composition: - **a- Water:** 90%, serving as a medium for materials being carried in the blood and having high capacity to hold heat, thus has a role in body temperature regulation. - **b- Plasma proteins:** 6% to 8% of plasma's total weight. - **c- Inorganic constituents:** about 1% of plasma's weight (Na+, Cl-, НСО₃, К+, Ca2+, Mg+ and others). - The remaining small percentage "2%" is composed of: - Nutrients e.g. glucose, amino acids, lipids and vitamins. - Waste products e.g. creatinine, bilirubin and nitrogenous substances as urea. - Dissolved gases (O2 and CO2). - Hormones. Most of these substances are merely being transported in the plasma. ### What is serum? - It is the fluid remaining after whole blood clots and the clot is removed. - It has the same composition as plasma except that its fibrinogen and clotting factors II, V and VIII are removed. ### PLASMA PROTEINS - These are important components that normally remain in the plasma, where they perform many valuable functions. - They do not exit through the narrow pores in the capillary walls because they are the largest of the plasma constituents. - The plasma proteins exist in a colloidal dispersion. - Total protein concentration in blood is 6-8 g/dl. - There are three groups of plasma proteins: 1) Albumin: 4-4.5 gm/dl 2) Globulin: 2.5 gm/dl. It is subdivided into a1, a2, B1, B2 and y globulins. [A/G ratio is 1.2-1.6). 3) Fibrinogen: 0.3 g/dl. - Other plasma proteins include prothrombin, other clotting factors, hormones and others. - The concentration of plasma proteins is kept constant because their rate of breakdown is equal to formation. ### Site of synthesis of plasma proteins: - The plasma proteins are synthesized by the liver with the exception of the y-globulins, which are produced by lymphocytes, one of the types of white blood cells. ### Hypoproteinemia occurs in: - Prolonged starvation: - Liver disease, because hepatic protein synthesis is depressed. - In nephrosis, because large amounts of albumin are lost in urine. - Rarely, there is congenital absence of one or other plasma protein fraction e.g. congenital form of afibrinogenemia, characterized by defective blood clotting. ### Factors affecting albumin/globulin (A/G) ratio: - A/G ratio is reduced in: - In liver disease due to decreased synthesis. - In kidney disease due to increased loss of albumin in urine. - In infections as in typhoid and T.B due to increased synthesis of y globulin - A/G is increased in: - Hypogammaglobulinemia. - Acquired immuno-deficiency syndrome (AIDS). ### Functions of plasma proteins: - **1. Production of an effective osmotic pressure:** - Plasma proteins due to their relatively large molecular size do not diffuse through the capillary wall. Thus, by their colloidal osmotic pressure (mainly due to albumin, MW 70000) which is about 25 mmHg, they regulate the passage of water and diffusible solutes through the capillary wall. - **2. Blood viscosity:** It is mainly fibrinogen that helps in maintaining peripheral resistance and thereby the diastolic blood pressure (by preventing rapid flow of blood from arteries to veins during diastole). - N.B. Red blood cells are far more important regarding viscosity than fibrinogen is. - **3. Buffering function:** - Plasma proteins provide about 15% of the buffering capacity of the blood. - **4. Clotting of the blood:** - Fibrinogen, prothrombin and other clotting factors are important in the blood clotting process. - **5. Defensive function:** - Gamma globulins are immunoglobulins (which are important in the blood defense mechanisms). - **6. Maintain normal capillary permeability:** - Plasma proteins close the pores of the cement substance of capillaries, so diminished plasma proteins increase capillary permeability. - **7. Act as carriers** - Specific a and ẞ globulins bind and transport a number of substances in the plasma, preventing their rapid loss in urine, for example: - some hormones (e.g. thyroid hormone, gonadal and adrenocortical hormones) - metal ions (e.g. Fe++, Cu++, Ca++ and I-) - some molecules (e.g. fatty acids, amino acids, enzymes and bilirubin). - **8. CO2 carriage:** - Plasma proteins form carbamino compounds with CO2 (tissue): - CO2 (10%) + aminogroup (NH2) of plasma proteins, - ↓ - carbamino compounds - release CO2 to be expired - (CO2 + proteins in lung capillaries). - **9. Some plasma proteins have specific functions,** - e.g. anterior pituitary hormones, angiotensinogen, clotting factors and antibodies. - **10. Protein reserve:** - Can be used by the tissues for their protein metabolism.