Blood Clotting Mechanisms and Atherosclesrosis

8/3/2019 Blood Clotting Mechanisms and Atherosclesrosis

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When the plasma, red blood cellsand platelets flow from a cut theycome in contact with the tissue (e.gcollagen fibres). This causes therelease of substances which aidinflammontry resoponse. The twomost important are:

Serotonin - causes the muscle of thevessel to contract. This is essential inthe process as when the musclecontracts it cuts off the blood to thedamaged area. This allows it to healfaster without disruption of the flowof blood.

Thromboplastin - needed for therelease of fibrin. It initially catalysesthe conversion of prothrombin tothrombin (the right amount ofcalcium ions need to present for thisreaction to take place.) Thrombinacts on another protein calledfibrinogen and converts it to fibrin.Fibrin is necessary for the blood to

clot successfully. Fibrin acts as aglue and keeps the differentplatelets and cells in place. Morecells get trapped and make theblood clot.

Proteins in the platelets contractmaking the structure tighter andtougher.


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Endothelial wall isdamaged this causes

them to agregate due tonegative feedback

Platelets which then come intocontact with the components of

the tissue e.g. the collagenfibresthis causes them to

break out in large numbers andrelease...

Serotonin (which causes thesmooth muscle of the vessel

to contract ) and ...

Thromboplastin

Thromboplastin is anenzyme which catalyses the

reaction between calciumand prothrombin to make...

Thrombin...

Thrombin is anotherenzyme which catalyses

the conversion offibrinogen to fibrin...

Fibrin forms a meshwhich traps platelets,

red blood cells andforms a clot...

The proteins in theplatelets contract

toughening the clot.


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What is it and how is it formed?

Atherosclerosis is the obstruction of the arteries bylocalised deposits of fatty material (including cholesterol)

on their inner walls. Atherosclerosis is associated with high

blood levels of cholesterol, particularly in the form of low-

density lipoprotein (bad cholesterol); it can result in heartfailure if it affects the coronary arteries.

It can begin in late childhood and continue throughout life.

Atherosclerosis usually occurs in arteries rather than veinsbecause the blood in the arteries flows fast under high

pressure, which puts more strain on the endothelium lining

which can cause small areas of damage. Whereas, in theveins the blood pressure is much lower so damage to the

endothelium lining is much less likely.

Damage is caused to thevessel wall

The bodys inflammatoryresponse is stimulatedand white blood cellsarrive at the site of the

damage

These cells accumulatechemicals from the body- in particular cholesterol

Which leads to fattydeposits on the

endothelial lining of theartery (this fatty deposit

is called atheroma)

Fibrous tissue andcalcium salts also buildup around the atheroma

turning it into ahardened plaque

The plaque hardens thevessel wall around itmeaning it is then less

elastic

This is atherosclerosis


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Atherosclerosis is a disease of the arteries in which fatty

material is deposited in the vessel wall, resulting in

narrowing and eventual impairment of blood flow. Severely

restricted blood flow in the arteries to the heart muscle

leads to symptoms such as chest pain. Atherosclerosis

shows no symptoms until a complication occurs.


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Blood Clotting Mechanisms and Atherosclesrosis