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circulatory system blood vessels & blood (plasma is the liquid that…
circulatory system blood vessels & blood
blood vessels
1) ARTERIES these carry the blood away from the heart
2) CAPILLARIES these are involved in the exchange of materials at the tissue
there are three different types of blood vessel
3) VEINS these carry the blood to the heart
arteries carry blood under pressure
the walls are thick compared to the size of the hole down the middle
they contain thick layers of muscles to make them strong and elastic fibres to allow them to stretch and spring back
the heart pumps the blood out at high pressure so the artery walls are strong and elastic
capillaries are really small
3) they carry the blood really close to every cell in the body to exchange substances with them
4) they have permeable walls so substances can diffuse in and out
2) capillaries are really tiny too small to see
5)they supply food and oxygen and take away waste like co2
1) arteries branch into capillaries
6) their walls are usually only one cell thick this is increased that rate of diffusion by decreasing the distance over which it occurs
veins take the blood to the heart
2) the blood is at lower pressure in the veins so the walls don't need to be as thick as artery walls
3) they have a bigger lumen than arteries to help the blood flow despite the ower pressure
1) capillaries eventually join up to form veins
4) they also have valves to help keep the blood flowing in the right direction
red blood cells carry oxygen
3) they don't have a nucleus this allows more room to carry oxygen
4) they contain a red pigment called haemoglobins
2) their shapes is a biconcave disc this gives a large surface area for absorbing oxygen
5) in the lungs haemoglobin in body tissues the reverse happens oxyhaemoglobin splits up into haemoglobin and oxygen to release oxygen to the cells
1) the job of red blood cells is to carry oxygen from the lungs to all the cells in th body
white blood cells defend against infections
2) other produce antibodies to fight microorganisms as well as antitoxins to neutralise any toxins produced by the microorganisms
3) unlike red blood cells they do have nucleus
1) some can change shapes to engulf unwelcome microorganisms
platelets help blood clot
2) they help the blood to clot at a wounded to stop all your blood pouring out and to stop microorganisms getting in
3) lack of platelets can cause excessive bleeding and bruising
1) these are small fragments of cells they have no nucleus
plasma is the liquid that carries everything in the blood
5)HORMONES
6) PROTEIN
4) urea from the liver to the kidneys
7) ANTIBODIES and antitoxins produced by the white blood cells
3) carbon dioxide from the organs to the lungs
2) nutrients like glucose and amino acids these are the soluble products of digestion
1) red and white blood cells and platelets