Chapter 17 Continue Part 3

Hemophilia C

milder form about as common as both sexes

Intrinsic Pathway

occurs when lining of blood vessels damaged or roughened, and requires only substances found within blood

Thrombolytic Agents

clot-dissolving substances injected into body to break down blood clots already formed. Act by directly or indirectly activating Plasminogen

Hemophilia

refers to several different hereditary diseases in which blood clotting impaired due to lack of a Clotting Factor. Can result in episode of heavy bleeding after only minor trauma

3 stages of Blood Clotting

1. Formation of Prothrombin Activator (Prothrombinase) 2. Conversion of Prothrombin (a plasma protein and clotting factor II) into Thrombin (an enzyme) by Prothrombin Activator (an enzyme) and CA2+ ions 3. Conversion of Fibrinogen (a plasma protein and clotting factor I) into fibrin (H2O insoluble protein whose threads from mesh that traps blood cells and platelets --> Blood Clot) by Thrombin and Ca2+ ions.

Blood Clot Formation (2 positive feedback mechanisms)

1. accelerating formation of prothrombin activator, which in turn, speeds up Production of more Thrombin. 2. Activating Platelets, causing them to aggregate, and release substance that helps activate clotting factors --> Formation of Pothrombin activator --> more thrombin

Inactivation (inhibition of activated Clotting Factors)

Antithrombin III -- Plasma Protein that inactivates Thrombin; Protein C (protein also produced by Liver) and Antithrombin III inactivate other Coagulation Factors.

Undesirable Blood Clotting

Smooth Lining of Blood Vessels: prevents Platelet attachment and aggregation Production by Endothelial Cells by PGI2 (Prostacyclin): prevents Platelets attachment and aggregation Production by Endothelial Cells of Heparin

Platelet-Derived Growth Factor

another substance released by Platelets that stimulates growth of Smooth Muscle and Fibroblasts to repair damaged wall of blood vessel. Endothelial Cells then divide to form new lining of blood vessel

Hemophilia B

are sex-linked recessive diseases -- so more common in males than in females

Thrombus

blood clot that forms in unbroken blood vessels. can be dangerous, if impairs blood flow to vital organ

Thrombocytopenia

deficiency in number of circulating Platelets. Result in bleeding from small blood vessels through-out body even with normal body movements. Usually associated with Platelet count less than 50,000 per mm^3 of blood

Fibrinolysis

dissolution of blood clot, by the action of a protein-digesting enzyme that breaks down Fibrin in clot

Extrinsic Pathway

faster pathway (since has fewer steps) that occurs when blood vessels ruptured and tissue damaged, and begins with substances outside blood. outside blood vessels

Vitamin K

fat-soluble vitamin required for Blood Clotting, since needed for synthesis of Prothrombin and three other Clotting Factors by Liver

PF3 (Platelet Factor 3)

substance produced by activated Platelets that acts similarly to Tissue Factor in activating various Clotting Factors involved in formation of Prothrombin Activator

Hemophilia A (Classical Hemophilia)

the most common form (due to clotting factor VIII deficiency)

Embolus

thrombus that breaks free from site where formed, and carried in bloodstream. Embolus can also refer to gas bubble, piece of fat, or debris transported by bloodstream

Clot Retraction (Syneresis)

tightening of blood clot, occurs once clot formed due to Platelets contracting and pulling on Fibrin Threads. This squeezes Serum (Plasma without the Clotting Factors) out of clot, compacting it, and pulls broken ends of vessel closer together.

Removal of Clotting Factors

washed away by blood (clots usually form in areas where slow or little blood flow), or as with Thrombin, absorbed by Fibrin Threads of Clot