Veins, aretries and capillaries

Structure of veins capillaries and arteries, why they are needed, what they are for, adaptations for their jobs.

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Arteries, veins and capillaries
Your body transports blood through blood vessels, the three main types of blood vessel are
called, arteries, veins and capillaries. They take oxygen rich blood to your cells, deliver the
oxygen and take back to waste blood to your heart. Arteries veins and capillaries can easily
be distinguished, and they all have very different jobs in transporting the blood around your
body, each one is adapted for it particular job.
Arteries take the oxygen rich blood all around your body
to deliver the oxygen. The blood in arteries moves at a high pressure and therefore the
structure of an artery is adapted for this reason. An artery has three layers they are:
Smooth Endothelium layer (Tunica intima)
Muscle and elastic tissue (Tunica media)
Connective tissue (Tunica adventia)
Arteries have a narrow lumen so a high pressure can be maintained. The first layer is a
smooth endothelium layer, this layer reduces friction. The layers in an artery are thicker than
a vein; this is because of the pressure the blood in arteries travels at. The thick muscle layer
is smooth; the muscle can contract to squeeze the blood along. The muscle layer also has
elastic fibres present, so the muscle can stretch and recoil to its original shape. The folded
lining also allows the vessel to stretch and recoil. The last layer is the connective tissue,
there is a lot of collagen in arteries and this is where it is found. The collagen keeps it elastic
and strong. The collagen stops it from bursting and also allows it to withstand a high blood

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The three layers in veins are the same as in arteries but
they are also different. The three layers are not as thick in veins as the blood is travelling at a
much lower pressure. A vein is not as strong and cannot stretch and recoil. There is less
collagen in the connective tissue, less elastic fibres in the muscle layer and the lumen is
much wider. The veins carry deoxygenated blood back to the heart from the capillaries.…read more

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