plasma proteins.pdf

BLOOD Blood is a part of the body fluids present inside the cardiovascular system. * Physical Properties of the Blood: 1- Volume: about 5.5 liters represents 7-8% of the total body weight. 2- Colour: red in color due to presence of hemoglobin in the red blood cor...

BLOOD Blood is a part of the body fluids present inside the cardiovascular system. * Physical Properties of the Blood: 1- Volume: about 5.5 liters represents 7-8% of the total body weight. 2- Colour: red in color due to presence of hemoglobin in the red blood corpuscles. Arterial blood is bright red than venous blood due to presence of oxyhaemoglobin. 3- Opacity: blood is opaque due to presence of cells. 4- PH: slightly alkaline. PH is about 7.4. 5- Viscosity: blood viscosity is 3 - 5 times as water. This is due to cellular components and plasma proteins. 6- Specific gravity: is 1060 for whole blood, 1090 for cells and 1030 and for plasma. 7- Plasma osmotic pressure: is 5500 mmHg. * General functions of the blood: 1- Transport medium of the body: a- Transport gases (respiration): carry O2 from the lung to the tissue and carry CO2 in the opposite direction. b- Transport nutrients: carry absorbed food from the gastrointestinal tract (GIT) to the tissues. c- Transport vitamins and hormones from the from the GIT to the tissues. So helping regulation of metabolic processes of the body d- Transport excretory materials (waste products) to the excretory organ. Non-volatile materials as urea, creatinine and uric acid are carried to the kidney.Volatile materials as ether and alcohol are carried to the lung. e- Transport heat: librated heat from the metabolic processes in specific site of the body is transported to the whole body via the blood. So helping in regulation of body temperature. 2- Defensive Functions: Achieved by white blood cells (WBCs) through phagocytosis of microorganisms or formation of antibodies against invaders. 3- Haemostatic functions: Haemostasis means stoppage of bleeding caused by blood vessel injury. This is achieved through platelets and its contents of clotting factors. 4- Homeostatic functions: Homeostasis means keeping the composition of internal environment constant. This is achieved by: a- Maintenance of acid base balance by keeping the pH of the body fluids constant. b- Regulation of water balance. c- Continuous exchange of substances between interstitial fluid and blood and between blood and external environment through lungs, kidneys and GIT. d- Blood glucose homeostasis. e- Blood calcium homeostasis. 5- Share in production of peripheral resistance by its viscosity so, maintain normal arterial blood pressure. COMPOSITION OF THE BLOOD The blood consists of cellular elements suspended in clear yellow fluid called plasma. * Cellular elements (45%): a- RBCs: 5 millions/mm3. b- WBCs: 4000 - 11000/mm3. c- Platelets: 150000 - 300000/mm3. * Plasma: It is the fluid part of the blood. It forms 5% of the of the body weight and 55% of the blood volume (3500ml). * Plasma constituents: PLASMA Water (90%) Dissolved solutes (10%) Organic substances (9.1%) Inorganic substances (0.8%) Na+, Cl-, Ca++, HCO3-, and Plasma protein (7.1%) Lipids, hormones, PO4- enzymes, nutrients and waste product (2 %). * Formation of blood: occurs in the following sites; 1- Bone marrow: Is the site of blood formation (main site) in adults and called (medullary haemopoiesis). 2- Liver and spleen: Is the site of blood formation in fetal life (extramdullary haemopoiesis). PLASMA PROTEINS The normal level of plasma proteins is 6 - 8 gm/dl. * Types of plasma proteins: The plasma proteins include albumin, globulin, fibrinogen and prothrombin. - Albumin is abundant, 3.5 - 5 gm % (average 4 gm %) and its mw is 64000 - 70000. - Globulin is less abundant, 2.3 - 3.5 gm % (average 2.7 gm %) and its mw is 90000- 156000. It has three types; alpha 1&2, beta 1&2 and gamma globulin. - Fibrinogen is least abundant, 0.3 - 0.4 gm % and its mw is 340000 - 400000. - Prothrombin is the least abundant, 10mg % and its mw is 350000. * different types of plasma proteins. Plasma proteins Concentration Molecular weight 1- Albumin 3.5 - 5 gm % 64000 - 70000 2- Globulin 2.3 - 3.5 gm % 90000 - 156000 3- Fibrinogen 300 - 400 mg% 340000 - 400000 4- Prothrombin 10 mg% 350000  A/G ratio: Normally it is 1.2 by electrophoresis and 1.6 - 1.7 by chemical separation. * Clinical Importance of A/G Ratio: 1- Decreased A/G ratio: occurs due to a- Decreased albumin as liver failure (decreased synthesis) and nephritic syndrome (increased loss of albumin). b- Increased globulins as severe infection. 2- Increase A/G ratio: - Occurs in congenital agammaghlobulinaemia and AIDS due to decrease globulin. Functions of Plasma Proteins I-Carriage and preservation of important substances: Plasma proteins act as carrier for important substances in the blood as hormones, minerals and vitamins so, they act as reservoir source of these substances. This function is important for: 1-Allowing transport of these substances to their utilization or storage sites. 2- Preserve them i.e. combine with theses preventing their rapid diffusion to the tissues and preventing their rapid loss in urine. II- Buffer Function: - Any buffer system consists of weak acid and strong base. The plasma proteins are present in the blood in the form of proteinic acid and Na proteinate so, they act as buffer system. Plasma proteins produce 7-15% of buffer functions i.e. converting strong acids to weak acids aiming to maintain Ph of the blood as follow; lactic acid + Na proteinate Na lactate + proteinic acid (weak acid). NaOH + proteinic acid Na proteinate + H2O. III- Regulation of capillary permeability: - Plasma proteins close the capillary pores so, it limit their permeability. - Decreased plasma protein levels leads to increased capillary permeability which may lead to edema as liver failure and nephritic syndrome. IV- Nutritional functions (protein reserve): plasma protein could be utilized by the tissues for gluconeogenesis in prolonged starvation. V- CO2 carriage: Plasma proteins carry CO2 as carbamino compounds. IV- Specific functions: Each plasma protein has specific functions as follow: 1- Production of osmotic pressure (28mmHg): - It is the function of albumin because it has the highest concentration and the smaller mw i.e. has the largest number of molecules and largest osmotic pressure. - The total osmotic pressure of plasma is 28 mmHg. - 25-28 mmHg is produced by plasma protein (colloid osmotic pressure) - Plasma proteins have lesser osmotic pressure however, it is of great 2- Defensive functions: gamma globulins (γ globulins). - γ globulins are antibodies that protect the body against invading microorganisms. 3- Haemostatic function: fibrinogen and prothrombin. - Fibrinogen and prothrombin are essential for blood clotting. 4- Production of blood viscosity: fibrinogen and globulin. - Plasma proteins especially fibrinogen are essential for production of peripheral resistance aiming at maintenance on normal arterial blood pressure.