right auricle-~r-'"\~--blood vessels_~_~_Ieftauricle....-~--'T-Ieftventricleright ventriclethe cells of the body. As a result, it has picked up wastesubstances. Eventually
these wastes (mostlycarbondioxide) must go to the lungs to beeliminatedby
exhalation (breathing out) and to the kidneys where the liquid wastes are
extracted,to beeliminatedin urine. Liquid wastes are alsoeliminatedby the
skin, passing off as"sweat."
The blood passes from the right auriclethrougha valve into the lower
right chamberof theheart,the right ventricle. Bymuscularcontractionsof
thethicker,lowerpartof theheart,thisbloodispumpedto the lungs.
Inthe lungs, thebloodexchanges the waste gas,carbondioxide, for fresh
oxygen from the air we inhale (breathein). This fresh oxygenmustbe dis-
tributedto all the cellsofthe body.
Blood carrying fresh oxygen returns to the left upper chamberofthe
heart,the left auricle. Fromthere, it passes througha valve into the left
ventricle, the lower leftpartofthe heart.
The thick muscular walls of the left ventricle contract rhythmically,
sending the fresh, oxygen-carryingbloodto allpartsof the body.
Inthis way each cellofthebodyof the steer, and ofourbodies, too, is
suppliedby the bloodwith the oxygen it needs in orderto function. Each
cell has a means of getting rid of its waste matter,for the bloodpicks it up
and takes it to organs ofthe body especiallyadaptedto throwingoff waste
products(the lungs, the kidneys and the skin).