Leukocyte Disorders Leukopenia Abnormally low WBC count drug induced by

Leukocyte disorders leukopenia abnormally low wbc

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Leukocyte Disorders Leukopenia Abnormally low WBC count: drug induced by glucocorticoids or chemo Leukemias Abnormally high WBC count Cancerous conditions involving WBCs Platelets Small fragments of megakaryocytes Formation is regulated by thrombopoietin produced by liver and kidney Form a temporary platelet plug that helps seal breaks in blood vessels Circulating platelets are kept inactive and mobile by NO and prostacyclin from endothelial cells of blood vessels Hemostasis: pathway to stop the bleeding of a damaged blood vessel 1 st step: Vascular Spasm 6/1/2018 Page 6
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BIO 202IN: Human Anatomy and Physiology II Vasoconstriction of the damaged blood vessel o Caused by smooth muscle in the wall of the blood vessel contracting Triggered by: Direct injury to vascular smooth muscle Chemicals released by endothelial cells and platelets 2 nd Step: Platelet Plug Formation At site of blood vessel injury: Platelets stick to exposed collagen fibers Swell, and become sticky, and release chemicals which attract more platelets This is a positive feedback cycle that continues until the hole is plugged 3 rd Step: Coagulation *0 Formation of a clot *1 Prothrombin is converted to thrombin *2 Thrombin is an enzyme that converts fibrinogen to fibrin. *3 Platelet plug is reinforced with fibrin threads which traps platelets, RBCs and plasma Coagulation Phase is triggered by tissue-damaging events Circulating clotting factors are activated Calcium is required Intrinsic pathway Activated by factors present within the blood, like activated platelets Extrinsic pathway Activated by exposure to tissue factor (TF) from tissues outside the blood Bypasses several steps of the intrinsic pathway, so is faster Clot Retraction *0 Platelets pull on the fibrin strands, squeezing serum from the clot *1 Serum is plasma minus fibrinogen and clotting factors Clot Repair *2 Platelet-derived growth factor stimulates division of smooth muscle cells and fibroblasts to rebuild blood vessel wall *3 Vascular endothelial growth factor stimulates endothelial cells to multiply and restore the endothelial lining Fibrinolysis: Removal of unneeded clots by plasmin (a fibrin-digesting) after healing has taken place Clot Formation Limited by: Smoothness and structure of endothelial lining of blood vessels Swift removal and dilution of clotting factors caused by rapidly moving blood Anticoagulants remove thrombin Most thrombin gets bound to fibrin Antithrombin III and heparin inactivate circulating thrombin and other procoagulants Thromboembolytic Conditions Thrombus : clot that develops and persists in an unbroken blood vessel 6/1/2018 Page 7
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BIO 202IN: Human Anatomy and Physiology II Deep vein thrombosis May block circulation, leading to tissue death Embolus : a thrombus freely floating in the blood stream An embolism blocks a blood vessel
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