com www.GOALias.blogspot.com www.GOALias ... - fun learning

www.GOALias.blogspot.comKidneyUretercontains water and salts. Boojho hasseen that sometimes in summer, whitepatches are formed on our clothes,especially in areas like underarms.These marks are left by salts present inthe sweat.Does sweat serve any other function?We know that the water kept in anearthen pot (matka) is cooler. This isbecause the water evaporates from thepores of the pot, which causes cooling.Urinary bladderUrethraUrinary openingFig. 11.6 Human excretory systemtube-like ureters. It is stored in thebladder and is passed out through theurinary opening at the end of amuscular tube called urethra (Fig. 11.6).The kindeys, ureters, bladder andurethra form the excretory system.An adult human being normallypasses about 1–1.8 L of urine in 24hours, and the urine consists of 95%water, 2.5 % urea and 2.5% other wasteproducts.We have all experienced that we sweaton a hot summer day. The sweatPaheli wants to knowwhether other animals alsourinate?The way in which waste chemicals areremoved from the body of the animaldepends on the availability of water.Aquatic animals like fishes, excrete cellwaste in gaseous form (ammonia)which directly dissolves in water. Someland animals like birds, lizards,snakes excrete a semi-solid, whitecoloured compound (uric acid). Themajor excretory product in humansis urea.Sometimes a person’s kidneys maystop working due to infection orinjury. As a result of kidney failure,waste products start accumulating inthe blood. Such persons cannotsurvive unless their blood is filteredperiodically through an artificialkidney. This process is called dialysis.127TRANSPORTATIONIN ANIMALSAND PLANTS127