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Blood clotting
When a blood vessel is damaged the flow of
blood has to be stopped to minimise blood
loss and pathogens getting in.
There are blood cells, plasma and platelets
in the blood. These all stick together to
`plug' the damaged vessel.
Steps explained.... -->…read more

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When the plasma and blood cells and platelets flow from a cut
they come in contact with the tissue or components of the tissue
for example the collagen fibres. Because of this the platelets and
the tissue release substances which help the process. The two
most important are:
Serotonin and Thromboplastin.
Serotonin- this substance causes the muscle of the vessel
contract. This is essential in the process as when the muscle
contracts it cuts off the blood to the damaged area. This allows it
to heal faster without disruption of the flow of blood.
Thromboplastin- is needed for the release of fibrin. The
thromboplastin initially catalyses the conversion of prothrombin
to thrombin (the right amount of calcium ions need to present for
this reaction to take place.) Thrombin acts on another plasma
protein called fibrinogen and converts it to fibrin. Fibrin is
necessary for the blood to clot successfully. Fibrin acts as a
`glue' and keeps the different platelets and cells in place. More
cells get trapped and make the blood clot.
Proteins in the platelets contract making the structure tighter and
http://www.youtube.com/watch?v=--bZUeb83uU and simple
flowchart…read more

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Endothelial wall is damaged
Platelets come into contact with the
components of the tissue e.g. the
collagen fibres ­ this causes them
to break out in large numbers and
Serotonin (which cause the
smooth muscle of the
vessel to contract ) and ...
Thromboplastin is an enzyme
which catalyses the reaction
between calcium and
prothrombin to make...
Thrombin is another enzyme
which catalyses the conversion
of fibrinogen to fibrin...
Fibrin forms a mesh which
traps platelets, red blood
cells and forms a clot...
The proteins in the platelets
contract toughening the
clot.…read more

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What is it and how is it formed?
Atherosclerosis is the obstruction of the arteries by localised 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 heart failure if it
affects the coronary arteries.
It can begin in late childhood and continue throughout life.
Atherosclerosis usually occurs in arteries rather than veins because 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 the veins the blood pressure is much lower so damage to the
endothelium lining is much less likely.
Which leads to fatty
The body's inflammatory
These cells accumulate deposits on the endothelial
Damage is caused to the response is stimulated and
chemicals from the body- lining of the artery (this
vessel wall white blood cells arrive at
in particular cholesterol fatty deposit is called an
the site of the damage
The plaque hardens the Fibrous tissue and calcium
vessel wall around it salts also build up around
This is atherosclerosis
meaning it is then less the atheroma turning it into
elastic a hardened plaque…read more

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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.…read more

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