Physiology 1 - Blood Lecture 1 PDF

Physiology 1 Blood Lecture 1 – Introduction Dr Ahmed Hussein 00 Dr. A. Hussein – Blood  Physiology 1 Introduction Blood is a vital fluid found in humans and...

Physiology 1 Blood Lecture 1 – Introduction Dr Ahmed Hussein 00 Dr. A. Hussein – Blood  Physiology 1 Introduction Blood is a vital fluid found in humans and other animals that provides important nourishment to all body organs and tissues and carries away waste materials Composition of blood 1) Plasma  55% 2) Cells  45% » WBCs - White blood cells (leucocytes). » RBCs - Red blood cells (erythrocytes). » Platelets (thrombocytes). Plasma 1- Water 90% 2- Plasma proteins 8% 3- Organic substances 1.1% as: a. Nutrients:  As digested food substances. b. Waste products:  As urea and cellular waste products. c. Other constituents:  e.g. Hormones, vitamins, lipids and enzymes. 4- Inorganic substances: 0.9% » as (Na+, Cl-, HCO3-). 01 Dr. A. Hussein – Blood  Physiology 1 Plasma proteins Protein Concentration Albumin 4-4.5 gm% (highest) Globulins Alpha 1 and 2, beta 1 and 2 2.5–2.7gm %. and gamma globulins. Fibrinogen 200-400 mg% Prothrombin 10 mg% The functions of plasma proteins 1. Nutrition 2. Hemostasis. 3. Blood viscosity. 4. suspension of RBCs 5. Transport of important elements (carrier). 6. Immunity. 7. Regulation of capillary permeability. 8. Osmotic function. Transport of Regulation of Special functions  Iron  Prothrombin → hemostasis - Capillary permeability  Ca2+,  Fibrinogen → hemostasis - Acid-base balance  Hormones & viscosity (Buffer function)  suspension of  globulins → immunity & RBCs viscosity  albumin → Osm. P. 1- nutrition:  Plasma proteins are used in protein metabolism. 2- Hemostasis (Blood clotting) Fibrinogen, prothrombin  essential for the coagulation process. 02 Dr. A. Hussein – Blood  Physiology 1 3- Blood viscosity:  Fibrinogen and globulin play an important role in viscosity.  Viscosity is important in: » maintenance of arterial blood pressure. 4- suspension of RBCs  Important for ESR  ESR is dependent on fibrinogen and globulin 5- Carrier (transport of important elements):  plasma proteins act as  carrier for hormones as thyroxin, vitamin A & minerals  preventing their rapid elimination (loss) in the urine. →  their half-life. 6- Immunity Gamma globulins  Used to exert passive immunity. 7- Regulation of capillary permeability: » plasma proteins close the pores in the cement substance in the capillary wall » so; they maintain the normal capillary permeability » ↓ plasma proteins → ↑capillary permeability 8- Osmotic function: Osmotic pressure of plasma proteins is important for » the reabsorption of water within the capillaries » antagonizes the filtering force of capillary blood pressure. Albumin is responsible for most of the osmotic pressure of the plasma 03 Dr. A. Hussein – Blood  Physiology 1 due to: » High concentration » has the smallest molecular weight. Small molecular size = great number of molecules Haemo = Bleeding. Hemostasis Stasis = Stoppage. Def.: means stoppage of bleeding (=prevention of blood loss), when a blood vessel is injured Mechanisms: 1) Vascular spasm (vasoconstriction) of the injured vessel 2) Platelet plugs formation 3) Clot formation 4) clot retraction 5) Repair of the injured blood vessel 1- Vascular spasm of the injured vessel  If the blood vessel is injured  its wall be contracted to reduce the blood loss.  This local vasoconstriction is produced by: a) Local myogenic contraction of the blood vessel. b) Local nervous reflex. c) Vasoconstrictor substances:  They are released by platelets e.g. serotonin & thromboxane A2 2- Platelet plugs formation  injury of blood vessel  the endothelium is removed and the underlying collagen fibers are exposed.  When platelets are exposed to the collagen fibers in vascular wall  platelet plug formation occurs. 04 Dr. A. Hussein – Blood  Physiology 1 Platelet plug passes through the following stages: A. Platelet adhesion:  The platelets become sticky and adhere to collagen in the injured wall. B. Platelet activation:  The platelets begin to swell, and develop pseudopods. C. Platelet aggregation:  Platelets secrete ADP and thromboxane A2, which activate more and more platelets and adhere to the originally activated platelets. 3- Clot formation  Clots are formed by: - conversion of the soluble fibrinogen into insoluble fibrin network with blood cells in its meshes 4- Clot retraction  means shrinkage of the blood clot to decrease the lumen of damaged vessel. It is caused by: a- Retractozyme that secreted by platelets. b- Contraction of platelets themselves.  due to activation of their contractile proteins (actin, myosin and thrombosthenine) probably by thrombin and calcium. Repair of damaged blood vessel  Fibroblasts, vascular endothelial and smooth muscle cells grow by the effect of platelet-derived growth factor (PDGF).  Fibrous tissue is formed within 1-2 weeks. Join us on telegram via: https://t.me/DrHussein52 05 Dr. A. Hussein – Blood