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The Kidneys and Homeostasis (B4)
Water and salt enter the body mainly in ………………….. and drinks. The kidneys are the ……………………… organs
involved in controlling the amount of water and salt and removing …………………..urea from the blood. Urea is
produced in the …………….……. from the breakdown of excess …………………….. (amino acids) which the body is
unable to store. These substances are removed from the blood by the kidney and flow out as a liquid called
…………..…..……… it then passes down a two tubes called the …….……………..… and into the muscular bladder
where it is ……………………. . The regulation and removal of these substances in the ………..………… stream is
carried out by millions of tiny ……………………………. called kidney …………………….. or nephrons. These work by
………………………… out of the blood small ...................... such as water, glucose, ……….....………. and salt (as ions).
As this liquid flows through the tubules all of the ..……………..………… is reabsorbed back into the blood as is
some of the ……………………….. and salt. None of the urea is ………………………..…….. because of its toxicity and it
passes completely through the tubule and eventually out of the kidney. The blood also contains other
components such as ……………….………… and blood cells but because of their ……………………….. size they remain in
the blood at the initial …………………….……. stage unlike the smaller molecules mentioned earlier. The amount
of water reabsorbed back into the blood is controlled by a hormone called ………………… .
toxic
water
food structures liver tubules stored
unlike excretory
blood
proteins
filtering
molecules urine ureters
filtration
glucose
large
urea ADH
reabsorbed
On the diagram below write: F where filtration takes place, RG where glucose is reabsorbed and
RW where water is reabsorbed.