Blood & Lymphatic System Module BMS201 Lecture 1 PDF

Blood & Lymphatic System Module BMS201 Topic (1) RBCs and Anemia Blood Physiology Lecture 1 Sem 3 (Blood and lymphatic module, NMU) Blood Def. It is a complex reddish fluid tha...

Blood & Lymphatic System Module BMS201 Topic (1) RBCs and Anemia Blood Physiology Lecture 1 Sem 3 (Blood and lymphatic module, NMU) Blood Def. It is a complex reddish fluid that circulates continuously inside the CVS. Volume:  About 5600 ml in a 70 kg man i.e. 8% of the BW. General functions of the blood:  It has 4 main functions; 1) It is the major transport medium in the body: →it carries; i) O2 and CO2→ respiratory function. ii) Glucose and other nutrients → nutritive function. iii) Metabolic end products as urea → excretory function. iv) Hormones → regulation of metabolism. 2) Haemostatic Function:  It stops bleeding from injured blood vessel.  It is carried out by clotting factors and platelets. 3) Homeostatic Function:  It keeps the composition of the internal environments constant.  This is achieved by the continuous exchange of substances ( ) the interstitial fluid and blood and ( ) the blood and the external environment through the GIT, lungs, kidneys and skin. 4) Defensive Function:  It defends against invasion by a wide variety of micro-organisms.  It is provided by WBCs through phagocytosis and antibody formation. Composition of the blood: It consists of 2 parts; A) Cells: → 45% of blood volume and include; i) RBCs:  5.4 millions/cmm in males. Blood Physiology Sem 3 (Blood and lymphatic module, NMU)  4.8 millions/cmm in females. ii) WBCs:  4.000-11.000/cmm. iii) Platelets:  150.000-300.000/cmm. B) Plasma: → 55% of blood volume and consists of; i) Water: →90% of plasma. ii) Solids : → 10% of plasma and include; a) Inorganic solids (0.9%): as Na, K, Ca, Cl, HCO3, PO4 and SO4. b) Organic solids (9.1%): such as;  Plasma proteins.  Lipids as FFA, cholesterol, etc….  Other as glucose, amino acids, vitamins, hormones. Plasma Proteins Types: They include 4 main types: a) Albumin b) Globulins: subdivided into; α1, α2, β1, β2, and γ globulins. c) Fibrinogen. d) Prothrombin. -In addition to small amounts of other proteins e.g. most of clotting factors. Concentrations of plasma proteins: The total plasma protein concentration is about 6-8 gm/dL. Concentration Molecular weight (gm/dl) (Dalton) Albumin 3.5 - 5.0 69,000 Globulins 2.4 - 2.7 90.000-156.000 Fibrinogen 0.4 340.000 Prothrombin 0.01- 0.16 68.700 Sites of formation of plasma proteins: Blood Physiology Sem 3 (Blood and lymphatic module, NMU) a) Liver: It synthesizes albumin, fibrinogen, prothrombin and globulins except the γ globulins. b) Lymphatic tissue: Its plasma cells synthesize γ globulin or antibodies. Dynamic state and sources of plasma proteins: 1) Def.,  Plasma proteins are dynamic structures which undergo continuous breakdown and resynthesis.  The rate of formation and destruction is equal. 2) Breakdown:  Albumin is transported to the interstitial fluid by pinocytosis across the capillary walls.  About 6-10% of this exchangeable albumin is degraded daily inside the tissue macrophages into amino acids. 3) Synthesis:  The degraded albumin is replaced by hepatic synthesis of 200-400 mg/kg/day→ is a slow process. 4) Sources of plasma proteins: The amino acids needed for synthesis of plasma proteins are derived from; a) Food proteins:  Proteins of high biological value as those found in meat, milk and eggs (containing excess essential a a).  Plant proteins favor globulin formation. b) Tissue proteins:  They can act as a source for plasma proteins mainly during starvation.  They are mobilized to the liver and used for plasma protein synthesis. Blood Physiology Sem 3 (Blood and lymphatic module, NMU) Labile reserve proteins which are structurally similar to plasma proteins and stored in liver, can be mobilized within few hours from the tissues to the plasma in cases of acute protein losses as during haemorrhage. Albumin/Globulin Ratio (A/G Ratio) 1) Def., It is the ratio ( ) albumin and globulin concentrations in plasma. 2) Value: Normally it is about l.2-1.6. 3) Importance: Its is of clinical importance as it is altered in many diseases such as; i) It is decreased in: a) ↓ed albumin:  Advanced liver disease→ ↓ed formation of albumin.  Renal diseases→ loss of albumin in urine.  Burns → loss of albumin from skin.  Starvation → ↓ed protein intake. b) ↑ed globulins:  Severe infections → ↑ed γ globulins formation. ii) It is increased in:  Congenital agamma globulinaemia → ↓ed the globulin fraction. Blood Physiology Sem 3 (Blood and lymphatic module, NMU) General functions of plasma proteins 1) Regulation of blood volume and tissue fluid formation: Plasma proteins exert an osmotic pressure called colloidal osmotic or oncotic pressure across the capillary wall, because the capillary wall is relatively impermeable to them. This pressure is produced mainly by albumin because it has the greatest concentration and the smallest MW of all of plasma proteins. It is about 28 mmHg (19 mmHg is caused by albumin and 9 mmHg by Na ions held in plasma by the Donnan's effect). This pressure tends to pull water into the blood→ so it is important for the regulation of the blood volume and tissue fluid formation. 2) Blood coagulation: It is done clotting factors which are plasma proteins e.g. prothrombin and fibrinogen. 3) Defense (immunity): It is done by; a) γ globulins (or antibodies) → defend against micro-organisms. b) Complement system. 4) Buffering action: Plasma proteins are responsible for about 15% of the buffering power of the blood. Its buffering action is due to; a) The presence of free acidic (R-COOH) and basic (R-NH) groups in plasma proteins which are easily dissociated→ allow them to act as weak acids or bases depending on the pH of the plasma. At normal pH of plasma (7.4) the plasma proteins are -ve charged and act as anions (weak acids), thus combined with bases mainly (Na) forming the buffer system, (proteinic acid- Na proteinate) b) The presence of imidazole group of histidine residues in plasma proteins which is easily dissociated. They buffer any acid or alkali added to blood as follow; o Lactic acid + Na proteinate Na lactate + proteinic acid. (Strong acid) (Weak acids) Blood Physiology Sem 3 (Blood and lymphatic module, NMU) o Na OH + proteinic acid Na proteinate + H2O 5) Blood viscosity: ∙Value: The whole blood viscosity is about 3 times that of H2O and the plasma is about 1.5 times that of H2O. ∙Cause: Blood viscosity is due to red blood cells and plasma proteins. Fibrinogen is the main cause the blood viscosity more than other plasma proteins to the blood viscosity due to the elongated shape of its molecules. ∙Importance: This viscosity is important in the production of the peripheral resistance and helps to maintain arterial blood pressure. 6) Control of capillary permeability: The pores in the capillary walls are closed by plasma proteins → limits the capillary permeability. 7) Transport of important substances (Carrier functions): ∙Def, Plasma proteins transport many important substances as hormones, vitamins, minerals, from the sites of absorption or sites of synthesis to the sites of action or storage. ∙Examples: i) Albumin: It acts as a carrier for hormones (thyroxin & steroids), amino acids, vitamins and fatty acids. ii) Transferrin (β1-globulin): It transports iron in the blood. iii) Ceruloplasmin (α2-globulin): It transports copper in the plasma. iv) Steroid hormone-binding globulin: It acts as a carrier protein for steroid hormones. v)Apolipoprotein B: It acts as a carrier for lipoproteins. vi) Transcobalamine: It acts as a carrier for vit. B12. vii)Transthyretin (thyroid binding prealbumin): Blood Physiology Sem 3 (Blood and lymphatic module, NMU) It acts as a carrier for thyroid hormone. ∙Importance: a) It prevents the rapid loss of substances in urine because the plasma proteins are of large MW → cannot be filtered through the glomeruli. b) It provides a reservoir of the substance when needed. c) It makes the lipids and free fatty acids miscible with water and easily transported through plasma (watery medium). 8) Use of plasma proteins by the tissue:  The tissues constantly use plasma proteins for their protein metabolism.  There is a state of reversible equilibrium ( ) plasma proteins and the tissue proteins under normal or diseased conditions, so that the ratio of total tissue proteins to total plasma proteins remains constant =33:1. 9) Carriage of CO2:  CO2 combines with the amino groups of the plasma proteins→ carried as carbamino compounds (RNHCOOH).