B2 Circulatory System - Blood Vessles (page 32) Flashcards
What are Blood Vessels designed for?
designed for their function.
What are the Three different types of blood vessels, and what do they do?
1) Arteries - they carry the blood away from the heart.
2) Capillaries - these are involved in the exchange of materials at the tissues.
3) Veins - these carry the blood to the heart
Are Arteries strong or weak, explain your answer?
The heart pumps the blood out at high pressure so the artery walls are strong and elastic.
Explain what the Arteries walls look like?
they are thick compared to the size of the hole down the middle (the lumen).
They contain thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back. (see diagram on page 32).
Arteries branch into what?
Capillaries.
How big are Capillaries?
they are really tiny - too tiny to see.
What job do the capillaries have?
they carry the blood really close to every cell in the body to exchange substances with them.
Describe the capillarie walls and why are they like this?
they have permeable (very thin) walls, so substances can diffuse in and out.
They supply food and oxygen and take away waste like CO2.
(their walls are usually only one cell thick. This increases the rate of diffusion by decreasing the distance over which it occurs)
Describe capillaries?
they are really small, too small to see
they have a thin wall - only one cell thick.
they have very small lumen (hole)
and has nucleus of cell.
see picture on page 32.
What do Veins do?
They take blood back to the heart.
Capillaries eventually join up to form what?
veins. The blood is at lower pressure in the veins so the walls don’t need to be as thick as artery walls.
Do veins have bigger or smaller lumen than arteries and why?
they have bigger lumen than arteries to help the blood flow despite the lower pressure.
Why do veins have valves?
to help keep the blood flowing in the right direction.
(see diagram of vein on page 32, it shows the elastic fibres and smooth muscle, and valve).
You might get asked to calculate the rate of blood flow in your exam, so calculate the following:
1464 ml of blood passed through an artery in 4.5 minutes. Calculate the rate of blood flow through the artery in ml/min?
rate of blood flow = volume of blood ÷ number of munutes.
1464 ÷ 4.5 = 325 ml/min
how many miles of blood vessels do your body contain?
around 60,000 miles of blood vessels.
