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__mechanisms that occur in sequence when there is a blood vessel injury (can be an __ or it could be __)
Only efficient if it’s a __; if its large and there’s bleeding involved, GO GET HELP
- actual cut in the vessel
- plaque formation in the lining of the vessel
- small vessel
What are the three mechanisms?
- blood vessels spasm
- platelet plug formation
- clot formaiton
Blood vessels spasm: Step one of this phase
1. First thing that happens when BV injury is that the sympathetic nerves supplying that vessel will be stimulated and will cause vasoconstriction (muscle in wall of BV is going to contract and its going to close, but not completelyà spasm; slowing down passage of blood through area of injury)
Blood vessels spasm: Step Two
1. Chemicals also released by injured tissue that also supplements or enhances the spasming
What is the function of blood vessel spasm?
1. Function of first step: Relatively short lived event, but long enough to allow for second event to kick in; slow down blood long enough for second event to kick in
Platelet plug formation
- 1. Normally, platelets won’t stick to smooth lining, but they get sticky
- 2. However, they like to stick to roughened areas, such as when you have a cut or scratch (area of injury)
- a. or stick to plaque
- 3. They also start sticking to each other, forming a plug of injury
- a. That plug, if it’s a severed vessel, will help plug up the area that’s severed
- i. Slow down the loss of blood due to less blood going through
- 1. To actually form the clot, the background which is fibrin, involves a lot of steps
- a. Cascade of events that activates one cycle, which activates another, etc.
- 2. Process is called hemostasis: the stopping of bleeding
- 1. lack of clotting
- a. All factors (see slide 17 for explanation of factors) are needed to get to point; if one is missing, you can’t clot blood
1. __is least effective; __is most effective, but not in large bleeding amounts or cut or large vessel
a. __is dangerous, so we want to __ it
i. As healing is taking place, the clot starts __.
1. As its __, its __
- shrinking, retracting
- bringing together the severed area.
bring area of injury closer together
Clot Dissolution (Fibrinolysis
i. dissolving of the clot caused by protein, fribrinolysin