blood vessels Flashcards
function of arteries
carries blood from the heart to the organs
where are capillaries involved
in the exchange of materials at tissues
function of veins
carries blood from the organs to the heart
why are artery walls strong and elastic
as the heart pumps the blood out at high pressure
why do arteries contain thick layers of muscle and elastic fibres
1) to make them strong
2) allows them to stretch and spring back
why do capillaries form extensive networks that spread throughout the body
so they can squeeze into the gaps between cells. due to this they can then carry the blood really close to every cell in the body to exchange substances with them
why do capillaries have permeable walls and why are they usually one cell thick
1) substances can diffuse in and out
2) rate of diffusion is increased as the distance over the wall is decreased
what do capillaries supply and takeaway
1) food and oxygen
2) waste e.g co2
why don’t the walls in the veins need to be as thick as the walls in the arteries
as there is a low blood pressure
why do veins need a bigger lumen than arteries
to help the blood flow despite the low pressure
why do veins have valves
to ensure the right direction of blood flow
