Blood

Extrinsic factors

- called extrinsic because the tissue factor it requires is outside of blood. - triggered by exposing blood to a factor found in tissue underneath the damaged endothelium. the factor is factor III -Faster because it bypasses several steps of the intrinsic pathway. in severe trauma blood clot can form in 15 seconds

- Thromboembolic disorders:

- result in undesired clot formation

Instrinsic factors

-Called intrinsic because the factors needed for clotting are present within the blood. -triffrered by negatively charged surfaces such as activated platelets, collegen or glass. Slower because it has many intermediate steps

two hemostatic mechanisms that prevent clot from becoming uneccasarily large

1) swift removal of clotting factors 2) inhibition of activated clotting factors

heparin warfarin

1)usually used in hospitals, administered i injectible form. 2) taken orally, used as treatment to reduce stroke in those prone to atrial fibrillation, when blood pools in the heart.

Thrombus

Clot that develops and persists in an unbroken blood vessel

Phase 3

Fibrin mesh traps blood cells and effectively seals hole until blood vessel can be permanently repaired. Thrombin catalyzes the transformation of soluble clotting factor fibrinogen into fibrin. they then polmerize to form long hairlike, insoluble fibrin strands. Fibrin strands glue platelets together and make web that forms basis for clot. liquid plasma becomes gel-like and traps formed elements that try to pass through. Finally factor xiii binds fibrin strands tightly together forming a fibrin mesh.

critical natural clot buster used in Fibrinolysis

Plasmin

Platelet Plug Formation

Second step in Hemostasis. platelets play a key role in hemostasis by aggregation (sticking together). Intact endothelial cellls release nitric oxide and prostacyclin and restrict aggregation. Once they are damaged however, Collagen fibers are exposed and platelets adhere to collagen fibers. Platelets are then activated and swell and become spiked, and become stickier. They then release the chemicals : adenosine diphosphate (adp) and Serotonin and Thromboxane A2.

Vascular Spasm (what triggers it)

The first step in Hemostasis. Triggered by : 1) direct injury to vascular smooth muscle 2) chemicals released by endothelial cells and platelets 3) pain reflexes

Coagulation

Third and final step of Hemostasis. Reinforces platelet pluf with fibrin threads that act as molecular glue. Blood is transformed from liquid to gel by a multistep process called Clotting Factors. Although Vitamin K is not used directly in coagulation, 4 of the Clotting Factors need vitamin K for synthesis.

Adenosine Diphosphate

a potent aggregating agent that causes more plateles to stick to the area and release their contents

when the liver is unable to synthesize its usual supply of clotting factors....

abnormal and often severe bleeding occur -causes range from easily resolved vitamin K deficiency (in newborns) from total impairment of liver function (hepatitis or cirrhosis)

Aspirin

an antiprostaglandin drug that inhibits thromboxane a2 formation.

Thrombocytopenia

condition in which the number of circulating platelets is deficient. - causes spontaneous bleeding from small blood vessels all over the body. -even normal movements lead to widespread hemorrhage, evedenced by small purplish spots called (petechiae) - thrombocytopenia can arise from any condition that surpresses or destroys bone marrow such as bone marrow malignancy .

Thrombus (problems associated)

if thrombus is large enough it may block circulation to the cells beyond the occulsion and lead to death of tissues.

Outside the body, only the ________ pathway initiates blood clotting

intrinsic

Phase 1: Coagulation can be initiated by either __________ or _____________ pathways.

intrinsic or extrinisic pathways

Serotonin and Thromboxan A2

messengers that enhance vascular spasm and platelet aggregation

embolus

once a thrombus breaks away form the vessel wall and floats freely in the bloodstream

embolism

once embolus comes into contact with a blood vessel too narrow for it to pass through.

plasmin

produced when plasma protien plasminogen is activated.

Antithrombin III

protein present in plasma, quickly inactivates any thrombin from acting elsewhere

Phase 2

prothrombin activator catalyzes the conversion of a plasma membrane called prothrombin into the active enzyme thrombin.

fibrinolysis

removes uneeded clots when healing has occured. Without it, blood vessels would become completely blocked.

Nitric Oxide and Prostacyclin

secreted by the enothelial cells normally prevent platelet adhesion

Hemophilia

several hereditary bleeding disorders that have similar signs and symptoms

_______ endothelium prevents platelets from clining and piling up

smooth and intact

Vascular Spasm

spasm response is valuable because a strongly constricted blood vessel can stop blood loss for 20 to 30 minutes.

liver cells require ___________ to produce clotting factors

vitamin K

Clot retraction

within 30 to 60 minutes a platelet induced process called clot retraction further stabilizes clot. Platelets contain contractile protiens (actin and myosin), contract in same way as smooth muscles. PLatelets contract squeezing serum (plasma minus the protiens) from the mass and compact the clot and drawing ruptured edges of the blood vessel closer together.

Vitamin E quinone

•formed when vitamin E reacts with oxygen, is a potent anticoagulant