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Understanding Blood Physiology: Composition, Functions, and Plasma Proteins

Explore the composition of blood, normal values, functions, and roles of plasma proteins. Learn about hematocrit, plasma composition, and causes of low plasma protein concentration.

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Understanding Blood Physiology: Composition, Functions, and Plasma Proteins

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  1. IBLSModule 2nd year Medicine Phase II, MBBS 2nd year Medicine- IBLS Module May 2008

  2. Lecture 1: Introduction to Blood Physiology Objectives • By the end of this lecture the student should be able to: • Describe the composition of blood. • State normal values of blood and plasma volume. • Define hematocrit and state its normal value. • Describe the functions of blood as a tissue. • Describe the composition of plasma. • List types of plasma proteins. • State the normal plasma protein concentration. • Describe the functions of plasma proteins. • Outline the different causes of low plasma protein concentration. 2nd year Medicine- IBLS Module May 2008

  3. Blood • Blood is the only liquid tissue. • It represents about 8% of total body weight. • Average blood volume is 5 L in women and 5.5 L in men. • Blood is composed of cellular elements suspended in liquid plasma. • Average plasma volume is 3 L. • 99% of cellular elements are RBCs. 2nd year Medicine- IBLS Module May 2008

  4. Composition of the blood • Plasma: fluid part, 55% of total blood volume, mainly water, organic and inorganic substances. • Cellular elements: 45% of total blood volume. • RBC or erythrocytes (5x106/mm3) • WBC or leukocytes (3-10x103/mm3 ) • Platelets or thrombocytes (150-400x103/mm3) 2nd year Medicine- IBLS Module May 2008

  5. Hematocrit or packed cell volume • Definition: % of total blood volume occupied by RBCs. Normal value: Adult male: 47 % Adult females: 42 % 2nd year Medicine- IBLS Module May 2008

  6. Functions of Blood • Transport function: • O2 and nutrients to cells • CO2 and metabolic waste products away from cells • Hormones, drugs, etc… • Defensive function: • WBC and antibodies • Hemostatic function: • Stop bleeding (platelets and clotting factors) • Homeostatic function: • pH • Temperature • Plasma volume 7 7 7 2nd year Medicine- IBLS Module May 2008

  7. Plasma • Composition • Water: 90% • Solids: 10% • Organic substances 9.1%: • Plasma proteins 6-8% of plasma’s total weight • Nutrients (a.a., glucose, lipids, vitamins) • Waste products (creatinine, bilirubin, urea) • Dissolved gases (O2 and CO2) • hormones • Inorganic substances: 0.9% (Na, Cl, others) 8 2nd year Medicine- IBLS Module May 2008

  8. Plasma proteins • Normal concentration 7-7.5 g/dl • Plasma proteins are: • Albumins (3.5-5 g/dl) • Globulins α1, α2, β1, β2, γ • Fibrinogen • Most of the plasma proteins are synthesized in the liver. • Circulating antibodies (γ globulins) are synthesized by plasma cells (activated B-lymphocytes). 2nd year Medicine- IBLS Module May 2008

  9. Functions of Plasma proteins • Osmotic function: • plasma proteins (mostly albumin) exert an osmotic pressure across the capillary wall (colloid osmotic pressure or oncotic pressure). • Plasma volume regulation 2nd year Medicine- IBLS Module May 2008

  10. 2nd year Medicine- IBLS Module May 2008

  11. Buffer action: • help in keeping pH of blood constant. • plasma proteins act as acids (due to COOH) and act as alkali (due to NH2 group). • Defensive function: -globulins defend the body against microorganisms and their toxins. 2nd year Medicine- IBLS Module May 2008

  12. Blood clotting: prothrombin and fibrinogen are essential for blood clotting. • Contributes to blood viscosity: blood viscosity prevents the rapid flow of blood from arterial to venous system. Viscosity of blood contributes to the peripheral resistance which maintains diastolic BP. • Transport: carrier proteins for small molecules such as vitamins, hormones, trace elements and drugs. • Nutritive: used by the tissue during prolonged starvation. 2nd year Medicine- IBLS Module May 2008

  13. Hypoproteinema: low plasma protein concentration. • Causes: • Liver diseases • Renal diseases • Prolonged starvation • Congenital deficiency (e.g. afibrinogenemia 2nd year Medicine- IBLS Module May 2008

  14. Summary • What is the composition of the blood? • What is the normal blood volume, plasma volume? • What is hematocrit value? Normal value? • What are the general functions of blood? • What is the composition of plasma? • Describe plasma proteins in terms of their: • Types • Normal concentration • Sites of formation • Functions • What are the causes of hypoproteinemia?

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