Excretory Products and their Elimination (Excretory Products aur unka Elimination): Class 11 Biology Chapter 16 Hinglish mein

Wastes aur unhe nikaalne wale organs

Rajma-chawal ki ek plate ya paneer ki ek katori tumhe usse zyada protein de deti hai jitna tumhara body store kar sakta hai. Extra amino acids energy ke liye tod diye jaate hain, aur unka nitrogen ammonia ke roop mein alag ho jaata hai. Respiration se carbon dioxide aur paani banta hai, aur ek namkeen snack zaroorat se zyada $\mathrm{N}\mathrm{a}{\phantom{X}}^{+}$, $\mathrm{K}{\phantom{X}}^{+}$ aur $\mathrm{C}\mathrm{l}{\phantom{X}}^{-}$ le aata hai; phosphate aur sulphate ions bhi jama hote jaate hain. Inmein se kuch ko body se poori tarah nikalna padta hai, jabki baaki ko bas sahi level tak kam karna hota hai. Yeh chapter iske baare mein hai ki animals, aur khaas taur par humans, yeh balancing aur disposal (उत्सर्जन, excretion) kaise karte hain, aur ismein zyada dhyaan un wastes par hai jinmein nitrogen hota hai.

Animals extra nitrogen ko teen main molecules mein se kisi ek mein pack karte hain, aur har choice mein safety aur paani ke beech trade-off hota hai. Ammonia teeno mein sabse zyada zehreela hai aur bahut aasaani se ghul jaata hai, isliye yeh tabhi safe hai jab bahut saara paani ise turant baha le jaaye. Urea kaafi kam toxic hai aur kuch der body fluids mein reh sakta hai. Uric acid sabse kam toxic hai aur mushkil se ghulta hai, isliye ise lagbhag sookha bahar nikala ja sakta hai (Fig. 16.1).

Jo animals paani se ghire rehte hain, woh sabse simple option afford kar sakte hain. Kyunki ammonia itni aasaani se ghul jaata hai, yeh bas ammonium ions ($\mathrm{N}\mathrm{H}{\phantom{X}}_4{\phantom{X}}^{+}$) ke roop mein diffuse ho kar bahar nikal jaata hai, general body surface se ya fish mein gills se, aur aas-paas ka paani ise baha le jaata hai; kidneys lagbhag koi role nahi nibhaatin. Is tarah nitrogen ko mainly ammonia ke roop mein nikalna ammonotelism hai, aur aquatic insects, aquatic amphibians aur kai bony fishes ammonotelic hain.

Tum ureotelic ho. Tumhara liver ammonia ko urea mein badalta hai, blood urea ko kidneys tak le jaata hai, aur kidneys use filter karke urine mein daal deti hain. Doosre mammals, kai terrestrial amphibians aur marine fishes bhi yahi karte hain. Urea zameen par jeene ke liye theek hai: yeh ammonia se kahin kam toxic hai, isliye kuch der body fluids mein reh sakta hai aur bahut kam paani ke saath bahar nikal sakta hai. Kuch ureotelic animals to thoda urea kidney ke matrix mein rok kar rakhte hain taaki wahan ke fluid ko zaroori osmolarity par rakha ja sake, yeh idea tum Section 16.4 mein phir dekhoge.

Reptiles, birds, land snails aur insects aur bhi zyada paani bachate hain. Yeh uricotelic hain: inka nitrogen uric acid ke roop mein nikalta hai, pellet ya paste ki shakal mein, aur lagbhag koi paani waste nahi hota. Balcony ki railing par kabootar ki beet ka safed hissa zyadatar yahi uric acid paste hota hai.

Animal kingdom mein excretory structures

Poore animal kingdom par nazar daalo to is kaam ka equipment bahut alag-alag hota hai (Table 16.1). Invertebrates zyadatar simple tubes par nirbhar rehte hain; vertebrates mein kidneys hoti hain, jo kai tubules se bane complex organs hain. Design jo bhi ho, inmein se zyadatar organs ek saath do kaam karte hain. Nitrogenous waste nikaalne ke alawa, yeh body fluids ka volume aur ion content steady rakhte hain, is kaam ko osmoregulation (परासरण नियमन) kehte hain.

16.1 Human Excretory System

Tumhare apne excretory system ke chaar parts hain: ek jodi kidneys (वृक्क) jo urine banati hain, ek jodi ureters jo use aage le jaate hain, ek urinary bladder jo use store karta hai, aur ek urethra jisse woh body se bahar nikalta hai (Fig. 16.2).

Apne haath peeth par wahan rakho jahan sabse neeche ki ribs khatam hoti hain, spine ke dono taraf ek-ek, to tum lagbhag apni kidneys ke upar ho. Yeh abdominal cavity ki dorsal inner wall se sati rehti hain, aur last thoracic vertebra se third lumbar vertebra tak ke levels mein faili hoti hain. Har kidney band mutthi ke size ki reddish-brown bean jaisi hoti hai: lagbhag 10–12 cm lambi, 5–7 cm chaudi aur 2–3 cm moti, aur vazan 120–170 g. Bean ke concave inner side par jo notch hai woh hilum hai, aur ureter, blood vessels aur nerves sab isi se guzarte hain.

Kidney ke andar

Kidney ko lambai mein kaato to bahar se andar ki taraf teen zones dikhte hain (Fig. 16.3). Ek mazboot capsule surface ko lapete rehta hai. Uske neeche bahar wala cortex hai, aur uske andar andar wala medulla, jo kuch cone-shaped medullary pyramids mein bata hota hai. Paas-paas ke pyramids ke beech cortex andar ki taraf tissue ki patti ke roop mein ghusta hai, jinhe renal columns ya columns of Bertini kehte hain. Har pyramid ka sira ek cup jaise calyx (plural: calyces) mein nikla hota hai. Calyces renal pelvis ke projections hain, jo hilum ke theek andar ek chauda funnel-shaped space hai aur patla ho kar ureter ban jaata hai.

Nephron

Har kidney mein lagbhag das lakh microscopic tubes hoti hain jinhe nephrons (वृक्काणु) kehte hain. Nephron kidney ki functional unit hai: poori kidney jo karti hai, har nephron chhote scale par wahi karta hai. Har nephron ke do parts hote hain, capillaries ki ek gaanth jise glomerulus kehte hain aur ek lambi renal tubule (Fig. 16.4).

Ek nephron mein pehle blood aur phir filtrate ko follow karo. Blood renal artery ki ek patli branch, afferent arteriole, se aata hai, jo capillaries ki woh gaanth banati hai jise glomerulus kehte hain, aur blood ek patli efferent arteriole se bahar jaata hai. Glomerulus se nichoda gaya fluid Bowman's capsule pakad leta hai, jo ek double-walled cup hai aur glomerulus ko waise hi thaame rehta hai jaise judi hui hatheliyan ek ball ko. Dono milkar renal corpuscle banate hain, jise Malpighian body bhi kehte hain. Capsule se fluid kas kar coiled proximal convoluted tubule (PCT) mein jaata hai, phir ek hairpin, Henle's loop, ke descending aur ascending limbs se neeche aur wapas upar jaata hai, aur phir ek doosre coil, distal convoluted tubule (DCT), se ghoom kar guzarta hai. Kai DCTs ek seedhi collecting duct share karti hain; collecting ducts aapas mein judti jaati hain aur aakhir mein medullary pyramids ke siron par, calyces ke andar, renal pelvis mein khaali hoti hain.

Renal corpuscle, PCT aur DCT teeno cortex mein hote hain; sirf Henle's loop medulla mein utarta hai. Yeh kitna gehra jaata hai, isse nephrons do tarah ke hote hain (neeche ka comparison).

Efferent arteriole seedhe kisi vein tak nahi jaati. Yeh phir se branch ho kar tubule ke chaaron taraf peritubular capillaries ka ek baareek network banati hai. Is network ki ek patli vessel Henle's loop ke bagal mein neeche jaati hai aur U ki shakal mein wapas upar aati hai, yeh vasa recta hai. Isliye nephron mein blood ek ke baad ek do capillary beds se guzarta hai, pehle glomerulus aur phir peritubular network, aur agle teen sections mein dono ka role hai.

16.2 Urine Formation

Urine teen processes se banti hai, har process nephron ke apne part mein: renal corpuscle mein glomerular filtration, tubule se wapas blood mein reabsorption, aur blood se tubule mein secretion.

Glomerular filtration

Glomerulus ek pressure filter ki tarah kaam karta hai, aur pressure khud blood se aata hai: glomerular capillaries mein blood itne pressure mein hota hai ki fluid ko bahar dhakel de. Us blood ko Bowman's capsule ke andar ke space se teen layers alag karti hain (Fig. 16.5). Blood ke sabse paas capillary wall ka endothelium hai, sabse bahar capsule ka epithelium hai, aur dono ke beech dabi hui ek basement membrane hai. Capsule ke epithelial cells, podocytes, capillaries ko ek complex aapas mein fanse pattern mein lapette hain jisse sirf chhote-chhote gaps bachte hain, jinhe filtration slits ya slit pores kehte hain.

Is filter se kitna blood guzarta hai? Har minute lagbhag 1100–1200 mL, yaani us minute mein heart ka har ventricle jitna volume pump karta hai uska lagbhag paanchva hissa. Do organs ke liye jinka kul vazan sirf lagbhag 300 g hai, yeh bahut bada hissa hai.

Sirf plasma proteins aur blood cells itne bade hote hain ki paar nahi ja paate; paani, glucose, amino acids, salts aur urea sab paar ho jaate hain. Kyunki yeh chhantai molecules ke scale par hoti hai, ise ultrafiltration kehte hain.

Dono kidneys milkar ek minute mein jitna filtrate banati hain, woh glomerular filtration rate (GFR) hai. Ek healthy adult mein yeh lagbhag 125 mL per minute hota hai. Yeh kam lagta hai, jab tak ise poore din ke liye scale na karo:

GFR ko steady rakhna zaroori hai, aur nephron is kaam ke liye apna sensor rakhta hai. Har DCT ghoom kar wapas aati hai aur apne hi glomerulus ki afferent arteriole ko chhooti hai. Is contact point par dono walls ke cells specialised ho kar juxtaglomerular apparatus (JGA) banate hain. GFR girne par yeh JG cells renin release karte hain, jo ek chain ki pehli kadi hai jo glomerular blood flow ko tab tak badhati hai jab tak GFR wapas theek na ho jaaye. Section 16.5 poori chain ko follow karta hai.

Reabsorption aur secretion

Socho ki tum har din 180 L ka drum filtrate se bharte ho lekin urine ki sirf 1.5 L ki bottle khaali karte ho. Baaki 178.5 L, lagbhag 99 percent, wapas blood mein jaana chahiye; is wapsi ko reabsorption kehte hain. Sab kuch ek hi tarah wapas nahi aata. Glucose, amino acids aur $\mathrm{N}\mathrm{a}{\phantom{X}}^{+}$ jaise keemti solutes active transport se wapas laaye jaate hain, jismein tubule cells ki energy kharch hoti hai. Nitrogenous wastes sirf passively, apne concentration gradients ke saath, wapas aate hain, aur tubule ke pehle segments mein paani bhi passively peeche-peeche jaata hai (Fig. 16.6).

Traffic doosri direction mein bhi chalta hai. Tubule cells blood se $\mathrm{H}{\phantom{X}}^{+}$, $\mathrm{K}{\phantom{X}}^{+}$ aur ammonia ko filtrate mein secrete karti hain. Secretion urine formation ka asli step hai: kitna acid aur potassium nikaalna hai yeh tay karke kidney body fluids ka ionic balance aur acid–base balance steady rakhti hai.

16.3 Tubules ka Function

Tubule ke har hisse ke apne kaam hain. Inhe yaad rakhne ka sabse saaf tareeka hai filtrate ki ek boond ko ek-ek karke segments se follow karna (Fig. 16.6, Table 16.2).

Proximal convoluted tubule (PCT): bulk recovery. Lagbhag har useful nutrient yahin wapas aata hai, saath mein 70–80 percent paani aur electrolytes bhi. Itna load sambhalne ke liye iski wall simple cuboidal cells se bani hoti hai jinmein microvilli ka brush border hota hai, jo reabsorption ke liye surface area kai guna badha deta hai. PCT pH aur ion balance ko bhi tune karti hai: yeh filtrate se bicarbonate ($\mathrm{H}\mathrm{C}\mathrm{O}{\phantom{X}}_3{\phantom{X}}^{-}$) wapas kheench leti hai aur usmein $\mathrm{H}{\phantom{X}}^{+}$ aur ammonia daal deti hai.

Henle's loop: do limbs, ulte rules. Neeche jaate waqt paani nikal sakta hai lekin electrolytes lagbhag nahi, isliye filtrate zyada concentrated hota jaata hai. Upar aate waqt rule palat jaata hai: paani wall ke paar bilkul nahi ja sakta, jabki electrolytes actively ya passively nikal jaate hain, isliye filtrate zyada dilute hota jaata hai. Ascending limb mein reabsorption sabse kam hota hai, kyunki jo salt yeh chhodta hai uske peeche paani nahi ja sakta. Phir bhi wahi salt asli point hai: yeh medulla ki tubules ke beech ke fluid, medullary interstitium, ko high osmolarity par rakhta hai.

Distal convoluted tubule (DCT): fine-tuning. Yeh segment kitna $\mathrm{N}\mathrm{a}{\phantom{X}}^{+}$ aur paani wapas leta hai yeh conditional hai: jab body mein inki kami ho to zyada, jab bahut ho to kam. PCT ki tarah yeh bhi $\mathrm{H}\mathrm{C}\mathrm{O}{\phantom{X}}_3{\phantom{X}}^{-}$ ko blood mein lautata hai, aur filtrate mein selectively $\mathrm{H}{\phantom{X}}^{+}$, $\mathrm{K}{\phantom{X}}^{+}$ aur $\mathrm{N}\mathrm{H}{\phantom{X}}_3$ daalta hai, jisse blood ka pH aur sodium–potassium balance target par rehta hai.

Collecting duct: aakhri faisla. Yeh aakhri stage tay karta hai ki urine kitni concentrated hogi. Duct cortex se le kar inner medulla tak jaati hai, lagaataar zyada namkeen surroundings se guzarte hue, aur jab body ko paani bachana hota hai, to bahut saara paani yahin se nikal jaata hai. Yeh thoda urea medullary interstitium mein bhi jaane deti hai, jo us region ki osmolarity high rakhne mein madad karta hai, aur DCT ki tarah yeh selectively $\mathrm{H}{\phantom{X}}^{+}$ aur $\mathrm{K}{\phantom{X}}^{+}$ secrete karti hai.

16.4 Filtrate ke Concentration ka Mechanism

Thar paar karta ek camel, ya bina water bottle ke dopahar bhar cricket khelne ke baad tum, dono ko waste nikaalte rehna hai aur saath hi kam se kam paani khona hai. Mammals yeh apne blood se zyada concentrated urine bana kar karte hain. Henle's loop aur vasa recta isse mumkin banate hain.

Key word hai countercurrent: do streams jo saath-saath ulti directions mein behti hain. Henle's loop mein ek hai, jismein filtrate ek limb mein neeche aur doosre mein upar jaata hai, aur vasa recta mein doosri, jismein blood yahi karta hai. Paas-paas rehne ki wajah se yeh do hairpins medullary interstitium ko aisi osmolarity par rakhte hain jo gehraai ke saath badhti hai, cortex mein lagbhag 300 mOsmol/L se inner medulla mein lagbhag 1200 mOsmol/L tak. Iska zyadatar hissa NaCl aur urea se aata hai.

Gradient kaise banta hai

Ek simple model dikhata hai ki ek hairpin itna steep gradient kaise bana sakta hai (Fig. 16.7). Har level par ascending limb salt ko interstitium mein dhakelta hai lekin paani ko peeche nahi jaane deta, isliye interstitium ascending fluid se zyada namkeen ho jaata hai. Phir bagal wala descending limb tab tak paani khota hai jab tak woh namkeen interstitium ke barabar na ho jaaye. Akele yeh sirf ek chhota side-to-side farq banata hai. Lekin fluid chalta rehta hai, aur namkeen fluid ko aur gehraai tak le jaata hai, jahan agla round of pumping usmein aur jod deta hai. Round dar round, chhote sideways farq jud kar upar se neeche tak ek bada gradient bana dete hain, isiliye loop ko aksar countercurrent multiplier kehte hain.

Gradient ko banaye rakhna: NaCl aur urea

Solute ke do flows gradient ko apni jagah banaye rakhte hain (Fig. 16.8). NaCl Henle's loop ke ascending limb se interstitium mein nikalta hai. Vasa recta ke descending limb mein neeche behta blood is salt ka kuch hissa utha leta hai, aur vasa recta ke ascending limb mein wapas upar behta blood use interstitium ko lauta deta hai, isliye blood salt ko baha le jaaye bina medulla se nikal jaata hai. Urea bhi chakkar lagata hai. Thoda urea gehri collecting duct se interstitium mein leak hota hai, ascending limb ke thin part mein jaata hai, filtrate ke saath collecting duct tak aage badhta hai, aur phir se interstitium mein leak ho jaata hai.

NaCl aur urea ka yeh transport, jo Henle's loop aur vasa recta ki hairpin arrangement se mumkin hota hai, countercurrent mechanism hai. Iska fayda collecting duct mein milta hai. Jaise-jaise duct lagaataar zyada namkeen interstitium se neeche jaati hai, osmosis se usmein se paani kheench liya jaata hai, aur andar ki urine dheere-dheere zyada concentrated hoti jaati hai. Human kidneys original filtrate se lagbhag chaar guna concentrated urine bana sakti hain, 300 ke muqable lagbhag 1200 mOsmol/L.

16.5 Kidney Function ka Regulation

Kidneys kisi fixed setting par nahi chalti. Hypothalamus, JGA aur kuch kam had tak heart dwara chalaye jaane wale hormonal feedback loops unke kaam ko lagaataar adjust karte rehte hain (Fig. 16.9).

ADH: paani bachana

May mein ek lambi bus journey socho jismein koi water stop nahi hai. Tumhe lagaataar paseena aata hai aur body fluid kam hota jaata hai. Osmoreceptors, jo blood volume, body-fluid volume aur ion concentration par nazar rakhte hain, is badlaav ko pakad lete hain aur hypothalamus ko stimulate karte hain. Iske nateeje mein antidiuretic hormone (ADH), yaani vasopressin, neurohypophysis se blood mein aata hai. Iska target tubule ka aakhri hissa, DCT aur collecting duct, hai, jahan yeh zyada paani ko blood mein lautne deta hai. Urine mein kam paani pahunchta hai, isliye ADH diuresis ke khilaaf kaam karta hai, yaani bahut saari dilute urine nikalne ke khilaaf. Agle stop par ek bottle paani pi lo to loop ulta chalta hai: extra fluid osmoreceptors ko switch off kar deta hai, ADH release kam ho jaata hai aur kidneys zyada paani jaane deti hain.

ADH blood vessels ko bhi sankara karta hai. Isse blood pressure badhta hai, jo glomerulus mein zyada blood bhejta hai aur GFR ko badha deta hai.

Renin–angiotensin mechanism

JGA ek relay chalata hai, jo glomerular blood flow, glomerular blood pressure ya GFR girne par shuru hota hai. Pehle, JG cells enzyme renin ko blood mein release karte hain. Doosre, renin plasma protein angiotensinogen par kaam karke angiotensin I banata hai. Teesre, angiotensin I angiotensin II mein badal jaata hai, jo active product hai. Phir angiotensin II problem ko do tarah se theek karta hai. Ek powerful vasoconstrictor hone ke naate yeh blood vessels ko sankara karta hai aur glomerular pressure aur GFR ko wapas upar le aata hai. Yeh adrenal cortex ko aldosterone release karne ka signal bhi deta hai, jisse tubule ke distal parts zyada $\mathrm{N}\mathrm{a}{\phantom{X}}^{+}$ aur uske saath paani rokte hain; extra fluid blood pressure aur GFR ko aur badhata hai. Yeh poora relay renin–angiotensin mechanism hai.

ANF: brake

Heart iska jawaab deta hai. Agar atria mein extra blood bhar jaaye aur unki walls khinch jaayen, to walls atrial natriuretic factor (ANF) release karti hain. ANF blood vessels ko chauda karta hai (vasodilation), isliye blood pressure girta hai. Kyunki yeh pressure ko neeche kheenchta hai jabki renin–angiotensin use upar dhakelta hai, ANF us mechanism ko control mein rakhta hai.

16.6 Micturition

Ek lambi train journey socho. Urine har waqt bladder tak pahunchti rehti hai, aur jaise-jaise bladder bharta hai, uski wall khinchti hai. Wall mein maujood stretch receptors is khinchaav ki khabar central nervous system (CNS) ko dete hain, isiliye tumhe urge mehsoos hota hai. Lekin kuch nahi hota jab tak tum tay na karo ki sahi waqt aa gaya hai, kyunki release voluntary hai. Phir CNS motor signals bhejta hai jo ek saath do kaam karte hain: bladder wall ki smooth muscle contract hoti hai aur urethral sphincter relax hota hai, isliye urine urethra se bahar nikalti hai (Fig. 16.10). Urine nikalna micturition hai, aur ise chalane wala nerve circuit micturition reflex hai.

Table 16.3 ek healthy adult ke typical figures deta hai: roz 1–1.5 L halka peela, paani jaisa, thoda acidic fluid jiski apni smell hoti hai, aur jo 25–30 g urea bahar le jaata hai.

Doctors urine ko lagbhag blood ki report ki tarah padhte hain. Iski banawat kai conditions ke saath badalti hai, isliye ek routine urine test kidney ki problem aur metabolic disorders dono ka pata de sakta hai. Urine mein sugar aur ketone bodies (glycosuria aur ketonuria) diabetes mellitus ki taraf ishaara karte hain, jismein blood glucose itna badh jaata hai ki tubules use poora wapas nahi le paati.

16.7 Excretion mein Doosre Organs ka Role

Zyadatar kaam kidneys karti hain, lekin lungs, liver aur skin bhi wastes nikaalte hain (Fig. 16.11).

Lungs. Tumhare lungs bahut saari carbon dioxide saans ke saath bahar chhodte hain, har minute lagbhag 200 mL, aur har din kaafi paani bhi vapour ke roop mein kho dete hain. Shimla ki thandi subah tum saans chhodte waqt us vapour ko condense hote dekh sakte ho.

Liver. Body ki sabse badi gland bile ko disposal route ki tarah use karti hai. Ismein bile pigments bilirubin aur biliverdin, cholesterol, vitamins, drugs aur steroid hormones ke breakdown products jaate hain. Bile intestine mein jaata hai, isliye inmein se zyadatar faeces ke saath body se bahar nikal jaate hain.

Skin. Monsoon ki chipchipi dopahar mein tum apne upar ke hont par namak ka swaad le sakte ho. Sweat glands se nikla paseena zyadatar paani hota hai, jismein NaCl, thoda lactic acid aur urea ki zara si maatra ghuli hoti hai. Iska asli kaam evaporate ho kar body surface ko thanda karna hai, isliye jo wastes yeh le jaata hai woh bonus hain. Skin ka doosra secretion, sebaceous glands se nikla sebum, oily hota hai: yeh body se kuch sterols, hydrocarbons aur waxes bahar le jaata hai aur skin par ek protective film chhod deta hai.

16.8 Excretory System ke Disorders

Agar kidneys theek se kaam karna band kar dein, to blood mein urea jama hone lagta hai. Yeh condition, uremia, bahut nuksaandeh hai aur kidney failure tak le ja sakti hai. Aise patient ke blood se urea haemodialysis se saaf kiya ja sakta hai (Fig. 16.12).

Haemodialysis ek membrane ke paar diffusion se kaam karta hai. Dialyser ke andar, jise artificial kidney bhi kehte hain, blood porous cellophane ki ek coiled tube se behta hai jiske chaaron taraf dialysing fluid hota hai. Yeh fluid har tarah se plasma jaisa banaya jaata hai, sirf ek baat ko chhod kar: ismein koi nitrogenous waste nahi hota. Chhote molecules apne concentration gradients ke saath cellophane ke paar jaate hain, isliye urea aur doosre nitrogenous wastes, jo blood mein bahut hain aur bahar bilkul nahi, aasaani se bahar nikal jaate hain. Blood ko wahan le jaane aur wapas laane mein do extra steps lagte hain. Kisi convenient artery se nikaale gaye blood mein pehle heparin, ek anticoagulant, milaya jaata hai, taaki tubing mein woh jam na jaaye. Saaf hone ke baad normal clotting wapas laane ke liye usmein anti-heparin milaya jaata hai aur use pump karke ek vein mein wapas bheja jaata hai. Duniya bhar mein uremia wale logon ke liye isne bahut bade scale par jaan bachayi hai.

Dialysing fluid ka plasma se itna milna kyun zaroori hai? Agar usmein glucose ya salts na hon, to woh bhi blood se leak ho jaayenge. Wastes ke alawa sab kuch match karke fluid yeh pakka karta hai ki sirf wastes ke liye hi gradient ho.

Jab kidneys hamesha ke liye fail ho jaayen, to dialysis sirf waqt de sakta hai. Pakka ilaaj kidney transplantation hai, yaani ek donor ki healthy, kaam karti kidney patient mein lagana. Lene wale ka immune system nayi kidney ko bahari samajh kar us par hamla kar sakta hai, isliye doctors kisi kareebi rishtedaar ko donor ke roop mein prefer karte hain; isse rejection ka chance kam hota hai. Modern surgery aur medicines ne is complicated operation ko pehle se kahin zyada successful bana diya hai.

Summary se pehle chapter ki cause-and-effect chains khud dobara banao: filtrate ka raasta, ADH aur renin–angiotensin loops, ANF brake, micturition reflex aur dialysis circuit (Fig. 16.13).