biology unit 3

The heart:

1) The right atrium of the heart recives deoxygenated blood from the body through the vena cava..

2) The deoxygenated blood moves through to the right ventricle, which pumps it into the lungs via the pulmonary artey.

3) The left atrium ecives the oxygenated blood from the lungs through the pulmonary vein.

4) The oxygenated blood then moves through the left ventricle, which pumps it around the whole body via the aorta

5) The left ventricle has a much thickerr wall than the right ventricle. it needs more muscle because it has to pump blood around the whole body, where as the right ventricle only has to pump blood to the lungs. the valves prevent the backflow of blood.

Blood vessels:

Arteries: carry blood under pressure

the heart pumps the blood out at high pressure so the artery wall  is strong and elastic. the walls are thick compared to the lumen. they contain a thick layer of muscle to make them strong.

Capillaries: are really small and the arteries branch into them.

they carry the blood really close to every cell in the body in oder to exchange substances with them. they have permable walls to do this. the supply food and oxygen and take away wastes like co2. their walls are one cell thick and because of this it increases the rate of which diffusion happens.

Veins: take blood back to the heart

capillaries eventuallly join up to form veins. the blood is at lower pressure in the veins so the walls dont need to be as thick as arteries. they have bigger lumen then arteries to help blood flow dispite lower pressure. they also have valves to keep blood flowing in the right direction.

The kidneys:

During digeston your body breaks down poteins from food into amino acids. these amino acids are then reasembled to forrm new types of proteins that the body needs. however it may mean that not all of the amino acids are used to make proteins. therefore they are in excess to the bodys requirements. as the body cannot store them it gets rid of them.

ulterfiltration: a high pressue built uo which squezes water, uea, ions and suga out of the blood into the bowmns capsule. the membranes between the blood vessles and the bowmans capsuale act like filters, so big molecules like proteins and blood cells stay…