University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2019
Views:

480

Pages:

7
Author:

Kenley Davila

Clot Retraction and Dissolution • Clot retraction occurs within 30 minutes – pseudopods of platelets pull on fibers of fibrin which compacts the clot • Platelet-derived growth factor is secreted by platelets and endothelial cells – the growth factor is a mitotic stimulant for fibroblasts and smooth muscle that multiply and repair the damaged vessel • Fibrinolysis or dissolution of a clot – Fibrin is broken down by the enzyme plasmin – Plasmin is produced by the intrinsic enzyme kallikrein and the extrinsic enzyme TPA (tissue plasminogen activator) Blood Clot Dissolution Positive Feedback TPA Kallikrein in the plasma and TPA (tissue plasminogen activator) from damaged tissues quickly convert inactive plasminogen into plasmin Plasmin breaks down clots and promotes formation of more kallikrein Dissolving Clots • Streptokinase – Enzyme made by the Streptococcus bacteria dissolves clots when administered intravenously. – Relatively non-specific and digests many proteins. • Tissue plasminogen activator (TPA) – Specifically converts inactive plasminogen into the clot-dissolving enzyme plasmin – Now produced by transgenic bacteria. • Hementin – Anticoagulant produced by the giant Amazon leech, Haementeria. – Used to dissolve clots in cardiac patients. – Now produced in transgenic bacteria. Medicinal Leeches Removing Clots from a postsurgical hematoma Prevention of Clots • Platelet Repulsion: – platelets do not adhere to prostacyclin-coating that normally lines blood vessels • Thrombin Dilution: – thrombin is normally diluted by circulating blood • heart slowing, as during shock, can result in clot formation • slow venous return in legs due to prolonged sitting can also result in clot formation • Anticoagulants – heparin secreted by basophils and mast cells during inflammatory response interferes with formation of clotting factors (prothrombin activator) • Drugs like coumadin Hemophilia • Genetic lack of clotting factors – hemophilia A is missing factor VIII (83% of cases) – hemophilia B is missing factor IX (15% of cases) – hemophilia C is missing factor XI (rare) • Symptoms: – physical exertion can cause bleeding and excruciating pain • Treatments: – transfusion of plasma or purified clotting factors – factor VIII is now produced by transgenic bacteria Normal Blood Values Adults have 4-6 L of blood Female Hematocrit: 37-48% Hemoglobin: 12-16g/dL RBC count: 4.2-5.4 million/L Male 45-53% 13-18g/dL 4.6-6.2 million/L WBC count: 4,500-10,000/L neutrophils 60-70% eosinophils 2-4% basophils <1% lymphocytes 25-33% monocytes 3-8% platelet count: 130,000 to 400,000/L