WBC and Platelets PDF

WBC and Platelets Dr.Rasha Eldeeb Associate Professor of Physiology www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES  WBC and Platelets Learning Objectives: Define WBCs and list different types of...

WBC and Platelets Dr.Rasha Eldeeb Associate Professor of Physiology www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES  WBC and Platelets Learning Objectives: Define WBCs and list different types of WBCs Describe the process of leucopoiesis Describe the general function of WBCs List the variations in leucocytic count Define Platelets Describe platelet's structure and relate that to its function Define Haemostasis Explain the mechanisms of Haemostasis To Start with … What is leucocytes?  The leucocytes, also called white blood cells, are the mobile units of the body’s protective system They are formed partially in the bone marrow (granulocytes and monocytes and a few lymphocytes) and partially in the lymph tissue (lymphocytes and plasma cells) The real value of the white blood cells is that most of them are specifically transported to areas of serious infection and inflammation, thereby providing a rapid and potent defense against infectious agents General Characteristics of Leukocytes: Six types of white blood cells are normally present in the blood They are polymorphonuclear neutrophils, polymorphonuclear eosinophils, polymorphonuclear basophils, monocytes, lymphocytes, and, occasionally, plasma cells The polymorphonuclear cells, all have a granular appearance for which reason they are called granulocytes, or, in clinical terminology, “polys,” because of the multiple nuclei. How many WBC in the blood?  The adult human being has about 7000 white blood cells per micro-liter of blood [Ranging from 4000-11000/µ3 (in comparison with 5million red blood cells) Of the total white blood cells, the normal percentages of the different types are approximately the following: How is WBCs Formed? Leucopoiesis Now… What is The Function of WBCs ? Secondary Immune response Primary Immune response What are the Variations in WBC count? Leukopenia: It a condition characterized by decreased total WBCs count is to less than 4000/mm3 due to either inadequate formation or excessive break down due to : oDrugs (e.g. chloramphenicol) oExposure to x-rays and some radioisotopes o Diseases of bone marrow o Severe chronic infections Leukocytosis: It is a condition characterized by total WBCs count increased more than 11,000/mm3 It is physiological in pregnancy , after cold path and after meals, muscular exercise and it is pathological in cases of tissue damage , pyogenic infections….etc. Leukemia It is a condition characterized by malignant proliferation of WBCs, due to Uncontrolled leucopoiesis in bone marrow. Caused by: o Genetic predisposition o Chemicals e.g. benzene and its derivatives, asbestos , cytotoxic drugs, chloramphenicol o X-rays & radioisotopes exposure What is platelet?  Platelets (Thrombocytes) are minute discs 1 to 4 micrometers in diameter They are formed in the bone marrow through the Myeloid pathway from megakaryocytes, which are extremely large cells of the hematopoietic series in the marrow The megakaryocytes fragment into the minute platelets either in the bone marrow or soon after entering the blood, especially as they squeeze through capillaries The normal concentration of platelets in the blood is between 150,000 and 400,000 per microliter with an average of 250,000/ul.  Platelets (Thrombocytes) are minute discs 1 to 4 micrometers in diameter They are formed in the bone marrow through the Myeloid pathway from megakaryocytes, which are extremely large cells of the hematopoietic series in the marrow The megakaryocytes fragment into the minute platelets either in the bone marrow or soon after entering the blood, especially as they squeeze through capillaries The normal concentration of platelets in the blood is between 150,000 and 400,000 per microliter with an average of 250,000/ul. What is the function of the Plaletes?  When platelets come in contact with a damaged vascular surface, especially with collagen fibers in the vascular wall, the platelets immediately begin to swell; assume irregular forms with numerous irradiating pseudopods protruding from their surfaces Their contractile proteins contract forcefully and cause the release of granules that contain multiple active factors They become sticky so that they adhere to collagen in the tissues and to a protein called von Willebrand factor that leaks into the traumatized tissue from the plasma They secrete large quantities of ADP; and their enzymes form thromboxane A2 both in turn act on nearby platelets to activate them as well, and the stickiness of these additional platelets causes them to adhere to the original activated platelets  Therefore, at the site of any opening in a blood vessel wall, the damaged vascular wall activates successively increasing numbers of platelets that themselves attract more and more additional platelets, thus forming a platelet plug This is at first a loose plug, but it is usually successful in blocking blood loss if the vascular opening is small Then, during the subsequent process of blood coagulation, fibrin threads form. These attach tightly to the platelets, thus constructing an unyielding plug  Therefore, at the site of any opening in a blood vessel wall, the damaged vascular wall activates successively increasing numbers of platelets that themselves attract more and more additional platelets, thus forming a platelet plug This is at first a loose plug, but it is usually successful in blocking blood loss if the vascular opening is small Then, during the subsequent process of blood coagulation, fibrin threads form. These attach tightly to the platelets, thus constructing an unyielding plug What are the variations in Platelets count?  Thrombocytopenia purpura is a condition where platelet counts are lower than normal, potentially leading to mild to serious bleeding. This bleeding can happen inside the body (internal bleeding) or on the skin Several factors can cause a low platelet count, such as: o The bone marrow doesn't make enough platelets o The bone marrow makes enough platelets, but the body destroys them (autoimmunity) or uses them up o The spleen holds onto too many platelets. The spleen is an organ that normally stores about one- third of the body's platelets o A combination of the above factors What is Hemostasis? Stoppage of bleeding by forming blood clots in the wall of damaged blood vessels, meanwhile the rest of the blood is maintained in a fluid state within the vascular system The Mechanism: grl-stop-sign A. Local Vasoconstriction B. Temporary hemostatic plug Formation (platelet reaction) C. Definitive hemostatic plug formation ( Blood Coagulation) D. Repair of damaged blood vessel Clotting Mechanism ( Blood Coagulation) Learning Resources: 1. Marieb EN. Human Anatomy and Physiology, 9th Edition, Pearson International Edition; 2014. ISBN-13: 978-1-2920-2649-7 2. Guyton, Arthur C. Textbook of medical physiology / Arthur C. Guyton, John E. Hall.—11th ed. 3. Ganong's Review of Medical Physiology/Kim E. Barrett, Susan M. Barman, Scott Boitano and Heddwen L.Brooks,23rd ed. 4. Instructional Web site 5. Lectures PDF on Moodle 6. https://www.clinicalkey.com/#!/content/book/3-s2.0-B9780702031144000026  DISCLAMER The contents of this presentation, can be used only for the purpose of a Lecture, Scientific meeting or Research presentation at Gulf Medical University, Ajman. www.gmu.ac.ae