04 Plasma.pdf

Plasma & its functions Dr. Hader I. Sakr Associate professor, Medical Physiology  ‫ﺴﻢ ﷲ اﻟﺮﲪﻦ اﻟﺮﺣﲓ‬ ‫﴿ َواﺗ ُﻘﻮا ا َ ۖ َوﯾ ُ َﻌ ُ ُ َ ُ‬ ‫ا‬‫و‬ ‫ۗ‬ ‫ا‬ ‫ُ‬ ‫ﲂ‬ ‫ُ‬ ‫ﻤ‬‫ّ‬ ‫ِ‬ ‫ﻠ‬ ‫ﳾ ٍء َ ِﻠ ٌﲓ﴾‬ ‫ِ ُ ِّ‬ ‫ﲁ َْ‬ Learning objectives:...

Plasma & its functions Dr. Hader I. Sakr Associate professor, Medical Physiology  ‫ﺴﻢ ﷲ اﻟﺮﲪﻦ اﻟﺮﺣﲓ‬ ‫﴿ َواﺗ ُﻘﻮا ا َ ۖ َوﯾ ُ َﻌ ُ ُ َ ُ‬ ‫ا‬‫و‬ ‫ۗ‬ ‫ا‬ ‫ُ‬ ‫ﲂ‬ ‫ُ‬ ‫ﻤ‬‫ّ‬ ‫ِ‬ ‫ﻠ‬ ‫ﳾ ٍء َ ِﻠ ٌﲓ﴾‬ ‫ِ ُ ِّ‬ ‫ﲁ َْ‬ Learning objectives: Blood elements. Plasma composition. Plasma proteins types, synthesis and functions. Blood elements  Blood elements  Blood is the vital fluid tissue, which circulates within the cardiovascular system.  The total blood volume is about 5600 ml. in a 70 Kg adult man, constituting 8% of the body weight  Composition of the Blood: Blood is composed of two main parts. Blood (8%) Plasma Cells (3%) (5%) RBCs WBCs Platelets Plasma composition  Plasma composition  Plasma is a yellow clear fluid that contains a large number of ions, inorganic and organic molecules which are transported to various parts of the body.  The normal plasma volume is about 3500 ml in an average adult male (about 5% of the body weight).  Plasma clots on standing and the remaining fluid is the serum.  Plasma composition  Plasma is composed of: 1. Water: Constitutes 90% of plasma volume. 2. Inorganic substances: 0.9% of plasma volume. The chief plasma inorganic cation is sodium (Na+, average concentration of 145 mEq/L). The chief inorganic anions are chloride (Cl-, average concentration of 110 mEq/L), and bicarbonate (HCO3-, average concentration 27 mEq/L). Other anions are small amounts of phosphates and sulphates.  Plasma composition  Plasma is composed of: 3. Organic substances: 9.1% of plasma volume. Plasma proteins (see later). Plasma Lipids: Cholesterol, triglycerides, fatty acids, and phospholipids carried in the blood in combination with plasma proteins, forming lipoproteins (VLDL, LDL, and HDL). Other organic substances: glucose, amino acids, vitamins, enzymes, and wastes. 4. Gases: plasma contains soluble O2 and CO2. Plasma proteins types, synthesis and functions  Plasma proteins types, synthesis and functions  The concentration of plasma proteins is 7.2-7.4 gm/dl.  Plasma proteins types, synthesis and functions  Sites of Formation of Plasma Proteins 1. The liver is the main site for synthesis of plasma proteins. Albumin, fibrinogen, and 50% of globulins. 2. Gamma globulins which are the antibodies are formed in the plasma cells in the lymphoid tissue.  Albumin-Globulin Ratio (A/G Ratio) - The normal value for the A/G ratio ranges between 1.2 – 1.6. - This ratio could decrease or increase. Decreased ratio Increased ratio Decreased numerator (α) Increased numerator (α) Increased denominator (⅟α) Decreased denominator (⅟α)  Plasma proteins types, synthesis and functions Albumin-Globulin Ratio (A/G Ratio)  Plasma proteins types, synthesis and functions  Functions of Plasma Proteins (PPs) 1. Osmotic Function (colloidal osmotic/oncotic pressure) - PPs, mainly albumin are important in regulating fluid exchange across the capillaries. - That is important for tissue fluid formation and blood volume regulation. - The total osmotic pressure of plasma is 290 mmol /L. - Most of this osmotic pressure is due to crystalloids (Na+, …..). - PPs are responsible for only 25- 28 out of 5597mmHg. - It is the most effective as capillary membrane is impermeable to PPs because of the big MW. - Albumin is mostly responsible for the oncotic pressure as it has the greatest concentration & the smallest MW of all PPs. - 19 mmHg of the colloidal osmotic pressure is caused by albumin.  Plasma proteins types, synthesis and functions 2. Buffer function: - Plasma proteins are responsible for 15% of the buffering power of the blood. - At normal plasma pH of 7.4, PPs are negatively charged & act as anions (weak acids) that are combined with bases (mainly Na+) forming the buffer system: proteinic acid/Na proteinate. 3. Defensive function: Gamma globulins are responsible for defending the body against microorganisms and their toxins (humoral immunity). 4. Blood clotting: Fibrinogen, prothrombin and β-globulins.  Plasma proteins types, synthesis and functions 5. Blood viscosity: - Blood is 3X, while plasma is 1.5X as viscous as water. - It is important in producing the peripheral resistance and maintaining ABP. - The elongated-shaped fibrinogen molecules contribute more than other PPs to the viscosity of the blood. 6. Capillary function: - PPs are essential for the maintenance of normal capillary permeability. - The pores in the capillary walls are closed by PPs  limiting their permeability.  Plasma proteins types, synthesis and functions 7. Transport and conservation of important elements: - Plasma proteins e.g. albumin, α and β globulins act as carriers in the blood. - They transport important substances such as hormones, vitamins, lipids and minerals. - Binding of these substances to plasma proteins: 1. Prevents their rapid loss in urine. 2. Reduces the free active form. 3. Provides a reservoir that can be used when needed.  Plasma proteins types, synthesis and functions 8. Use of plasma proteins as a source of amino acids for the tissues (labile protein storage): - PPs act as a source for rapid replacement of tissue proteins in cases of tissue protein depletion. - They are engulfed by the liver cells and macrophages where they split into amino acids. - Amino acids are transported back to the blood to be taken and utilized by the tissues in building new proteins. Thus, plasma proteins function as a medium and represent a rapidly available source of amino acids to the tissues.  Conclusion Blood is a fluid tissue with many functions. Plasma is the fluid part of the blood with water forms 90% of it. Plasma proteins are of 4 types. Plasma proteins are formed in the liver (mainly) and RES. Plasma proteins have many vital functions. References Guyton and Hall, 13th edition. Unit V(25); 305-14. Ganong’s review of medical physiology 25th ed. Section I(2); 45-53. Thank You