Excretory Products and Their Elimination | hinglish NEET Notes | Class 11 Biology
This NEET-focused summary of Class 11 Biology Chapter – Excretory Products and Their Elimination clear notes provide karti hai ki kaise human body nitrogenous wastes jaise urea ko kidneys ke through eliminate karti hai. Excretory system, jo mainly ek pair of kidneys, ureters, urinary bladder, aur urethra se milkar bana hota hai, filtration, reabsorption, aur secretion mein nephrons ke through crucial role play karta hai. Key concepts include karte hain glomerular filtration, urine formation, aur hormonal regulation of kidney function by ADH aur aldosterone. Ye chapter micturition, lungs, liver, aur skin ke roles in excretion, aur major kidney disorders jaise kidney stones, uremia, aur renal failure bhi explain karta hai. Life-saving procedures jaise dialysis aur kidney transplantation bhi discuss kiye gaye hain, jo is topic ko NEET preparation aur CBSE, RBSE, etc. Class 11 Biology ke liye essential banata hai.
1. Excretory Products and Their Elimination – Powerful Insights on Nitrogenous Waste Removal
- Animals constantly kuch waste substances produce karte hain jaise ammonia, urea, uric acid, carbon dioxide, water, aur mineral ions jaise sodium (Na⁺), potassium (K⁺), chloride (Cl⁻), phosphate, aur sulfate. Ye substances ya toh metabolic activities ke result me generate hote hain ya excess food aur water ke through liye jaate hain. Animals ke survival aur internal balance ke liye ye waste materials ko completely ya partially eliminate karna crucial hota hai. Excretion kehte hain un processes ko jisme ye wastes body se remove hote hain, aur ye homeostasis maintain karne me vital role play karta hai. Inme se, nitrogenous wastes jaise ammonia, urea, aur uric acid especially important hote hain.
- Ammonia sabse toxic hota hai aur isko excrete karne ke liye zyada paani ki zarurat hoti hai. Uric acid, doosri taraf, sabse kam toxic hota hai aur minimal water loss ke saath remove ho jata hai, jo dry environments me rehne wale animals ke liye suitable hota hai.
- Ammonia ko body se remove karne ke process ko ammonotelism kehte hain. Organisms jaise bony fishes, aquatic amphibians, aur aquatic insects ammonotelic hote hain, matlab ye ammonia ko apna main nitrogenous waste ke roop me excrete karte hain. Kyunki ammonia highly soluble in water hota hai, ye easily body surface ya gills ke through diffuse ho jata hai, especially fishes me, ammonium ions ke form me. In organisms me, kidneys ka role minor hota hai ammonia ke removal me.
- Jab animals terrestrial life me adapt hue, toh unhone paani conserve karne ke liye highly toxic ammonia ko less toxic forms jaise urea ya uric acid me convert karna develop kiya. Mammals, terrestrial amphibians, aur marine fishes urea excrete karte hain aur unhe ureotelic animals kehte hain. In animals me, metabolism ke dauraan jo ammonia banta hai, wo liver me urea me convert hota hai, phir blood ke through kidneys tak transport hota hai, jahan filter hokar urine ke form me excrete hota hai. Kuch animals osmotic balance maintain karne ke liye thoda sa urea kidneys me retain bhi karte hain.
- Reptiles, birds, insects, aur land snails apna main nitrogenous waste uric acid ke form me produce karte hain. Inhe uricotelic animals kehte hain. Uric acid ek thick paste ya solid pellet ke form me excrete hota hai, jisme almost no water loss hota hai, jo dry aur water-scarce environments me unke liye highly beneficial hota hai. Ye adaptation unhe terrestrial ecosystems me survive karne me help karti hai, jahan water conservation critical hoti hai.
- Animal kingdom ka broad study batata hai ki alag-alag animals ne different types of excretory structures evolve kiye hain waste removal perform karne ke liye. Invertebrates me ye structures generally simple tubular systems hote hain, jabki vertebrates me excretory organs zyada complex aur well-developed hote hain, mainly kidneys ke form me.
- For example, protonephridia ya flame cells organisms jaise Platyhelminthes (flatworms jaise Planaria), rotifers, kuch annelids, aur cephalochordate Amphioxus me excretory organs ke roop me kaam karte hain. Ye flame cells mainly osmoregulation ke liye responsible hote hain, matlab body me water aur ions ka balance maintain karte hain.
- Ek aur common excretory organ hai nephridia, jo annelids jaise earthworms me paaya jata hai. Ye structures nitrogenous wastes remove karte hain aur internal fluid aur ionic balance regulate karne me bhi help karte hain. Insects me, including cockroaches, excretory function Malpighian tubules ke through perform hota hai. Ye tubules sirf nitrogenous wastes eliminate nahi karte, balki osmoregulation me bhi essential role play karte hain.
- Lastly, antennal glands, jinhe green glands bhi kehte hain, crustaceans jaise prawns me paaye jaate hain aur ye metabolic wastes ke excretion me help karte hain.
2. Introduction to the Human Excretory System
The human excretory system kuch main parts se milkar bana hota hai jo milkar waste materials jaise urea remove karte hain aur body ka internal balance maintain rakhte hain. Is system me two kidneys, two ureters, one urinary bladder, aur ek urethra shamil hote hain. Kidneys primary filtering organs hote hain jo blood ko clean karte hain by removing waste aur extra water, jisse urine banta hai. Har kidney se ek thin tube hoti hai jise ureter kehte hain, jo urine ko urinary bladder tak le jaati hai, jahan ye temporarily store hota hai. Jab bladder full ho jata hai, toh urine body se ek tube ke through pass hota hai jise urethra kehte hain. Ye saare organs milkar ek complete system banate hain jo continuously blood filter karke aur harmful substances eliminate karke body ko healthy rakhne me help karte hain.
3. Structure of Human Kidney and Nephron
- Kidneys humans me reddish-brown, bean-shaped organs hote hain jo abdomen ke andar, spine ke dono taraf deep located hote hain. Ye last thoracic vertebra aur third lumbar vertebra ke beech position me hote hain, aur abdominal cavity ke inner back (dorsal) wall ke close lie karte hain. Har adult human kidney ka size approx 10–12 cm long, 5–7 cm wide, aur 2–3 cm thick hota hai, aur iska average weight lagbhag 120 to 170 grams hota hai.
- Har kidney ke inner side par ek small notch-like opening hoti hai jise hilum kehte hain, jo ureter, blood vessels, aur nerves ke entry aur exit point ka kaam karti hai. Hilum ke just andar ek funnel-shaped cavity hoti hai jise renal pelvis kehte hain, jo cup-like extensions banati hai jise calyces (singular: calyx) kehte hain, jo urine collect karti hain.
- Kidney bahar se ek tough outer covering se protected hoti hai jise renal capsule kehte hain. Andar, kidney ke do main internal regions hote hain — outer cortex aur inner medulla. Medulla me cone-shaped structures hote hain jise medullary pyramids kehte hain, jo calyces me project karte hain. Cortex medullary pyramids ke beech extend hota hai renal columns ya Columns of Bertini ke form me.
- Har kidney me approx one million nephrons hote hain jo functional units hote hain aur urine formation ke liye responsible hote hain. Har nephron ke do main parts hote hain — glomerulus aur renal tubule. Glomerulus ek bunch of tiny capillaries hota hai jo afferent arteriole (renal artery ki ek small branch) se banta hai. Filtered blood glomerulus se efferent arteriole ke through bahar nikalta hai. Glomerulus ke around ek cup-like structure hoti hai jise Bowman’s capsule kehte hain. Glomerulus aur Bowman’s capsule milkar Malpighian body ya renal corpuscle banate hain.
- Bowman’s capsule se tubule continue hota hai ek highly twisted part ke roop me jise proximal convoluted tubule (PCT) kehte hain. PCT ke baad tubule ek U-shaped loop banata hai jise Henle’s loop kehte hain, jiske do parts hote hain — descending limb aur ascending limb. Iske baad tubule ka structure distal convoluted tubule (DCT) me continue hota hai. DCTs multiple nephrons se aake ek straight collecting duct me open hote hain, aur ye collecting ducts milkar renal pelvis me medullary pyramids ke through calyces me open hote hain, jahan se urine finally bahar nikalta hai.
- Malpighian corpuscle, PCT, aur DCT sab cortex region me located hote hain, jabki Henle’s loop medulla me extend hota hai. Zyadatar nephrons ka Henle’s loop chhota hota hai jo medulla tak barely pahuchta hai — inhe cortical nephrons kehte hain. Kuch nephrons ka Henle’s loop lamba hota hai jo medulla me deep jata hai — inhe juxtamedullary nephrons kehte hain.
- Efferent arteriole jo glomerulus se nikalta hai, wo renal tubule ke around ek capillary network banata hai jise peritubular capillaries kehte hain. Is network se ek small blood vessel nikalta hai jo Henle’s loop ke parallel run karta hai aur ek U-shaped structure banata hai jise vasa recta kehte hain. Cortical nephrons me ye vasa recta absent ya bahut chhota hota hai, lekin juxtamedullary nephrons me ye well-developed hota hai, aur urine formation ke dauraan water aur salt balance maintain karne me help karta hai.
4. Urine Formation – Process & Mechanism in Humans
Urine formation ka process humans me ek step-by-step mechanism hai jo har nephron ke andar kidney me hota hai. Ye process ensure karta hai ki waste products aur excess substances blood se remove ho jayein, jabki important substances jaise glucose, water, aur salts sahi amount me retain ho.
Urine banne ke liye teen main steps hote hain — glomerular filtration, reabsorption, aur secretion. Ye steps nephron ke alag-alag parts me hote hain aur milkar clean aur concentrated urine produce karte hain. Har step ka ek specific role hota hai blood ko filter karne aur body ka internal balance maintain karne me.
Glomerular filtration pehla step hai, uske baad selective reabsorption hoti hai useful substances ki, aur finally additional waste products urine me secrete kiye jaate hain, usse pehle ki urine collecting duct me pass ho.
These steps are detailed explained below there-
- Urine formation ka process start hota hai glomerular filtration se, jo nephron ke ek part glomerulus me hota hai. Ye pehla step hai jahan blood high pressure ke under filter hota hai. Lagbhag 1100 se 1200 ml blood per minute kidneys ke through filter hota hai — ye roughly ek-fifth hota hai total blood ka jo har side of heart se har minute pump hota hai. Glomerular capillaries me high blood pressure blood ko filter karne ke liye three layers se push karta hai — endothelium of blood vessels, epithelial lining of Bowman’s capsule, aur unke beech ek thin basement membrane. Bowman’s capsule ke inner lining me special cells hote hain jise podocytes kehte hain, jo aise arranged hote hain ki unke beech tiny gaps bante hain jise filtration slits ya slit pores kehte hain. Ye slits allow karte hain ki blood plasma ke almost sare parts (except proteins) Bowman’s capsule me pass ho jayein. Kyunki ye filtration bahut fine hota hai, is process ko ultrafiltration kehte hain.
- Donon kidneys se filtrate ka total amount per minute glomerular filtration rate (GFR) kehlata hai. Healthy person me GFR approx 125 ml per minute hota hai, matlab kidneys lagbhag 180 litres fluid per day filter karte hain. Lekin hum sirf 1.5 litres urine per day excrete karte hain, isliye lagbhag 99% filtrate kidney tubules ke through blood me reabsorb ho jata hai. Is step ko reabsorption kehte hain. Nephron tubules ki cells actively useful substances jaise glucose, amino acids, aur sodium ions (Na⁺) ko active transport se reabsorb karti hain, jabki nitrogenous wastes jaise materials passively absorbed hote hain. Water bhi passively reabsorb hota hai, mainly nephron ke earlier segments me.
- Ek aur important step hai tubular secretion. Yahan nephron tubules ki cells actively additional substances jaise hydrogen ions (H⁺), potassium ions (K⁺), aur ammonia ko forming urine me secrete karti hain. Ye step acid–base balance aur ionic composition of body fluids maintain karne ke liye vital hai.
- Kidneys me ek inbuilt control system hota hai jo stable GFR maintain karta hai. Ek structure jise juxtaglomerular apparatus (JGA) kehte hain, filtration regulate karne me help karta hai. Ye specialized cells se bana hota hai jo distal convoluted tubule aur afferent arteriole ke junction me hote hain. Agar GFR drop ho jata hai, toh JG cells ek enzyme renin release karte hain, jo blood flow aur filtration pressure restore karne me help karta hai, aur GFR ko normal level me le aata hai.
5. Functions of the Renal Tubules in Urine Formation
- Nephron tubules urine formation aur body ke internal environment maintain karne me vital role play karte hain. Proximal Convoluted Tubule (PCT) nephron tubule ka pehla part hai, jo simple cuboidal brush border epithelium se lined hota hai, jisse surface area absorption ke liye increase hota hai. Ye almost sare essential nutrients aur lagbhag 70-80% water aur electrolytes reabsorb karta hai. Ye blood pH aur ionic balance maintain karne me bhi help karta hai, by selectively secreting hydrogen ions (H⁺) aur ammonia (NH₃) filtrate me, aur bicarbonate ions (HCO₃⁻) reabsorb karta hai.
- Next part, Loop of Henle, do limbs se bana hota hai jinke alag functions hote hain. Descending limb water ke liye permeable hai lekin electrolytes ke liye nahi, isliye water reabsorbed hota hai aur filtrate concentrated ho jata hai. Ascending limb water ke liye impermeable hai, lekin electrolytes actively ya passively transport hote hain, jisse filtrate dilute ho jata hai jab wo ascend karta hai. Ye medullary interstitial fluid ki high osmolarity maintain karne me help karta hai, jo water reabsorption ke liye crucial hai.
- Distal Convoluted Tubule (DCT) conditional sodium ions (Na⁺) aur water reabsorb karne deta hai aur selectively hydrogen ions (H⁺), potassium ions (K⁺) aur ammonia (NH₃) secrete karta hai, jisse pH aur sodium-potassium balance blood me maintain hota hai.
- Finally, Collecting Duct cortex se medulla tak run karta hai aur large amount me water reabsorb karta hai, jisse urine concentrated hota hai. Ye thoda urea bhi medullary interstitium me pass hone deta hai, jo osmolarity me contribute karta hai. Iske alawa, ye selectively H⁺ aur K⁺ ions secrete karke blood pH aur ionic balance regulate karne me help karta hai. Overall, tubules ensure karte hain useful substances reabsorb ho aur waste remove ho, jo homeostasis maintain karta hai.
6. How the Kidney Concentrates the Filtrate
- Humans, especially mammals, me ek unique ability hoti hai ki wo highly concentrated urine produce kar sakte hain. Ye important hai kyunki ye body me water conserve karne me help karta hai. Is process me main structures Henle’s loop aur vasa recta hote hain, jo nephron (kidney ka basic filtration unit) ke parts hain. Ye dono structures milkar counter current mechanism ke through kaam karte hain.
- Henle’s loop me fluid (filtrate) apne do limbs — descending aur ascending — me opposite directions me flow karta hai. Similarly, vasa recta me blood bhi apne do limbs me opposite directions me flow karta hai. Ye opposite flow counter current pattern banata hai. Henle’s loop aur vasa recta ka close arrangement aur unka opposite flow kidney ke inner region me, jise medullary interstitium kehte hain, gradual concentration (osmolarity) increase karne me help karta hai. Ye concentration cortex (outer part of kidney) me approx 300 mOsm/L se inner medulla (innermost region) me 1200 mOsm/L tak badh jata hai.
- Is concentration gradient ko mainly create karne wale substances sodium chloride (NaCl) aur urea hote hain. Ascending limb of Henle’s loop me, NaCl actively surrounding interstitial fluid me transport hota hai. Ye NaCl phir vasa recta ke descending limb se pick up hota hai aur baad me ascending limb ke through interstitium me wapas aata hai. Similarly, urea bhi role play karta hai. Kuch urea thin ascending limb of Henle’s loop me enter karta hai, aur phir collecting tubule ke through interstitium me wapas transport hota hai. Ye cycling of NaCl and urea medullary region me steep concentration gradient maintain karne me help karta hai.
- Ye poora process, jahan NaCl aur urea ko specially move karke inner medulla ka osmolarity increase kiya jata hai, counter current mechanism kehlata hai. Ye mechanism important hai kyunki ye water ko easily collecting tubule se body me move karne me allow karta hai. Isse tubule ke andar ka filtrate zyada concentrated ho jata hai. Is tarah, kidneys urine produce kar pate hain jo original filtrate se 4 times zyada concentrated hota hai.
7. Hormonal Regulation of the Kidney
- Human body me ek smart system hota hai jo kidneys ke function ko regulate karta hai, ensuring ki fluid aur ion balance hamesha maintain rahe. Ye regulation hormonal feedback mechanisms ke through hoti hai, aur main parts jo involved hote hain wo hain hypothalamus, Juxta Glomerular Apparatus (JGA), aur kuch had tak heart bhi. Jab bhi body ke fluid levels ya salt concentration me change hota hai, osmoreceptors brain me ise detect karte hain. Agar body me bahut water loss hota hai (jaise sweating, bleeding, ya diarrhea ke wajah se), ye osmoreceptors activate ho jate hain. Ye hypothalamus ko signal bhejte hain ki ek hormone ADH (Antidiuretic Hormone) ya vasopressin release kare from neurohypophysis (posterior pituitary).
- ADH ka main kaam hai kidneys ko help karna water reabsorb karne me nephron ke latter parts se (especially collecting duct), jisse urine me kam water loss hota hai. Ye diuresis (excess urine production) prevent karta hai. Agar body me already enough fluid ho, toh ye osmoreceptors off ho jate hain aur ADH secretion stop ho jata hai, completing the negative feedback loop.
- Interestingly, ADH thoda blood vessels constrict bhi karta hai, jisse blood pressure increase hota hai. Higher blood pressure glomerular blood flow improve karta hai, jo glomerular filtration rate (GFR) badhata hai — matlab zyada blood kidneys se filter hota hai.
- Ek aur major regulatory system Juxta Glomerular Apparatus (JGA) ke through manage hota hai. Agar blood flow glomerulus me drop ho ya GFR decrease ho, toh JG cells ek enzyme renin release karte hain. Renin ek chain reaction start karta hai jahan angiotensinogen (blood me protein) ko angiotensin I me convert karta hai, jo phir angiotensin II me change hota hai. Angiotensin II ek powerful vasoconstrictor hai — ye blood vessels narrow karta hai, blood pressure raise karta hai aur GFR improve karta hai. Ye hormone adrenal cortex (adrenal gland ka part) ko signal deta hai aldosterone release karne ke liye. Aldosterone sodium (Na⁺) aur water reabsorption increase karta hai distal tubule se, blood volume aur pressure boost karta hai, aur normal GFR restore karne me help karta hai. Ye pura system Renin-Angiotensin Mechanism kehlata hai.
- Lastly, heart bhi role play karta hai. Jab blood flow ya fluid zyada hota hai, heart ke upper chambers (atria) ek hormone Atrial Natriuretic Factor (ANF) release karte hain. ANF vasodilation (blood vessels ka widening) cause karta hai, jisse blood pressure lower hota hai. Ye renin-angiotensin system ka natural check hai, jo body ko zyada salt aur water retain karne se rokta hai aur system ko balance me rakhta hai.
8. Process of Urine Release (Micturition)
- Urine ko body se remove karne ke process ko micturition kehte hain. Jab urine nephrons ke through kidneys me banta hai, ye ureters ke through travel karke urinary bladder me collect hota hai. Ye bladder ek storage sac ki tarah kaam karta hai aur urine ko hold karta hai jab tak body use release karne ke liye ready nahi hoti. Jaise-jaise urine bladder me fill hota hai, bladder ke walls stretch hote hain. Ye stretching special stretch receptors ko activate karta hai jo bladder wall me hote hain. Ye receptors signals bhejte hain central nervous system (CNS) ko, mainly brain aur spinal cord.
- CNS, apni taraf se motor signals bladder ke muscles ko contract karne ke liye bhejta hai, aur saath hi urethral sphincter (ek ring-like muscle jo urine flow control karta hai) ko relax karwata hai. Ye coordinated action urine release karta hai, jise micturition kehte hain. Is process me involved complete neural control ko micturition reflex kehte hain.
- Healthy adult me, lagbhag 1 se 1.5 litres urine per day excrete hota hai. Normal urine usually light yellow, watery, aur slightly acidic hota hai, jiska pH approx 6.0 hota hai. Iska characteristic smell bhi hota hai. Average, body lagbhag 25–30 grams urea per day urine ke through get rid karta hai, jo ek major nitrogenous waste product hai.
- Lekin kai health conditions urine ke composition, color, aur quantity ko affect kar sakti hain. Isliye urine tests medical diagnosis me commonly use hote hain. For example, urine me glucose ka presence, jise glycosuria kehte hain, aur ketone bodies (ketonuria) ka presence dono hi diabetes mellitus ke clear signs hain. Is tarah, urine analysis metabolic disorders aur kidney problems detect karne ka useful tool ban jata hai.
9. Importance of Accessory Excretory Organs in the Body
- Although kidneys main organs hain jo body se waste products remove karte hain, kuch aur organs bhi excretion me significant role play karte hain. Inme lungs, liver, skin, aur salivary glands shamil hain. Har ek apne unique way me certain types of waste materials remove karta hai.
- Lungs help karte hain excrete karne me large amount of carbon dioxide (CO₂) — lagbhag 200 mL per minute — jo cellular respiration ke dauran produce hota hai. CO₂ ke saath, lungs water vapor bhi expel karte hain, jo ek aur form of waste hai. Ye gas exchange body ka acid-base balance maintain karne aur gaseous waste remove karne ke liye essential hai.
- Liver, jo human body ka largest gland hai, kai excretory functions perform karta hai. Ye old red blood cells ko break down karta hai aur bilirubin aur biliverdin jaise substances produce karta hai, jo waste pigments hain. Ye cholesterol, broken-down steroid hormones, vitamins, aur drug residues bhi excrete karta hai. Ye substances bile me pack hote hain, jo small intestine me secrete hota hai aur finally feces ke through digestive waste ke saath eliminate hota hai.
- Skin excretion me apna part sweat aur sebaceous glands ke through play karta hai. Sweat glands watery fluid sweat secrete karte hain, jisme sodium chloride (NaCl), small amounts of urea, lactic acid, aur other waste products hote hain. Sweat ka main function body ko cool karna hai, lekin ye kuch nitrogenous aur salt-based wastes eliminate karne me bhi help karta hai. Dusri taraf, sebaceous glands oily substance sebum release karte hain, jisme sterols, hydrocarbons, aur waxes hote hain. Sebum mainly skin ko soft aur protect karta hai, lekin thoda oily waste excrete karne me bhi role play karta hai.
- Interestingly, humari saliva bhi choti amount me nitrogenous waste remove karne me help kar sakti hai, although ye primary excretory route nahi hai. Overall, jabki kidneys zyada kaam karte hain, ye additional organs body ke internal environment ko clean aur balanced rakhne me important support provide karte hain.
10. Common Problems Related to Human Excretory System
- Excretory system ka crucial role hai blood se harmful waste products filter karne me. Jab kidneys properly function nahi karte, ye waste products, especially urea, blood me accumulate hone lagte hain. Ye dangerous condition uremia kehlati hai, aur agar treat na kiya jaye, toh ye complete kidney failure me lead kar sakti hai, jo life-threatening situation hai. Is condition ko manage karne ke liye hemodialysis medical process use hota hai.
- Hemodialysis me, patient ka blood ek suitable artery se liya jata hai aur external filtering machine artificial kidney ya dialysing unit se pass hota hai. Machine me enter karne se pehle, anticoagulant jaise heparin add kiya jata hai taaki blood clot na ho.
- Dialyser ke andar, blood thin cellophane tubes ke through flow karta hai, jo coiled hote hain aur ek special dialysing fluid me surrounded hote hain. Ye fluid blood plasma ke same composition ka hota hai — lekin nitrogenous wastes jaise urea aur creatinine ke bina. Tubes ka porous cellophane membrane sirf choti molecules ko concentration gradient ke basis par pass hone deta hai. Kyunki dialysing fluid me nitrogenous waste nahi hota, ye wastes naturally blood se fluid me move karte hain, effectively blood ko clean karte hain. Blood purify hone ke baad, ye body me vein ke through return hota hai, anti-heparin add karke bleeding rokne ke liye. Hemodialysis duniya bhar me kidney malfunction patients ke liye life-saving solution ban gaya hai.
- Lekin, end-stage kidney failure ka best long-term solution kidney transplantation hai. Is method me, ek healthy kidney donor se surgically patient me transplant ki jati hai. Ideally, donor close relative hona chahiye taaki immune system ke organ rejection ka risk kam ho. Medical technology aur immunosuppressive drugs ke advances ki wajah se, kidney transplantation ka success rate recent years me greatly improve hua hai.
- Uremia aur kidney failure ke alawa, kuch aur common excretory system disorders bhi hote hain. Ek aisi condition hai renal calculi, jo kidney stones ke formation ko refer karti hai — hard masses of crystallised salts jaise oxalates kidneys ke andar. Ye urine flow block kar sakte hain aur severe pain cause karte hain. Dusri disorder hai glomerulonephritis, jo glomeruli (tiny filtering units in kidneys) ka inflammation hai. Ye condition kidneys ki filtering ability affect karti hai aur swelling, high blood pressure, aur blood in urine lead kar sakti hai.
11. Summary – Excretory Products and Their Elimination (Class 11 Biology)
Human body continuously produce karta hai various waste products jaise nitrogen-containing compounds, ions, carbon dioxide, aur excess water, jo remove karna zaruri hai taaki internal balance maintain rahe. Kis type ka nitrogenous waste organism excrete karta hai — ammonia, urea, ya uric acid — ye largely depend karta hai uske habitat aur water availability par. In wastes ko remove karne ke liye, animals ne different types ke excretory organs develop kiye hain, including protonephridia, nephridia, Malpighian tubules, green glands, aur vertebrates me kidneys. Ye organs sirf metabolic wastes remove nahi karte, balki acid-base balance aur ionic composition of body fluids maintain karne me bhi help karte hain.
Humans me, excretory system consist karta hai two kidneys, two ureters, a urinary bladder, aur urethra se. Kidney ka basic structural aur functional unit nephron hai, aur har kidney me over one million nephrons hote hain. Har nephron ke do main parts hote hain — glomerulus, jo afferent arteriole se banaye gaye capillaries ka bundle hai, aur renal tubule, jo double-walled Bowman’s capsule se start hota hai. Tubule divided hai proximal convoluted tubule (PCT), Henle’s loop, aur distal convoluted tubule (DCT) me. Kai nephrons ke DCTs ek collecting duct me drain karte hain, aur kai collecting ducts renal pelvis me open hote hain through medullary pyramids. Bowman’s capsule aur glomerulus milkar renal corpuscle ya Malpighian body form karte hain.
Urine ka formation nephron me teen major steps me hota hai: filtration, reabsorption, aur secretion. Filtration ek passive, non-selective process hai jo glomerulus me high blood pressure ki wajah se hota hai. Lagbhag 1200 mL blood har minute filter hota hai, jisse 125 mL filtrate banta hai, is rate ko glomerular filtration rate (GFR) kehte hain. Juxtaglomerular apparatus (JGA) GFR ko regulate karne me vital role play karta hai. Lagbhag 99% filtrate nephron ke various parts me reabsorbed hota hai. PCT responsible hai maximum reabsorption aur kuch selective secretion ke liye. Loop of Henle mainly help karta hai osmotic concentration gradient (300 se 1200 mOsmol/L) kidney me maintain karne me. DCT aur collecting ducts water aur electrolyte reabsorption ko fine-tune karte hain, jo osmoregulation me contribute karta hai. Nephron H⁺, K⁺, aur NH₃ ko filtrate me secrete karke pH aur ion balance regulate karta hai.
Ek important mechanism jo urine concentrate karne me help karta hai, wo hai counter current mechanism, jo descending aur ascending limbs of Henle’s loop aur vasa recta (loop ke around capillary network) ke beech hota hai. Jab filtrate descending limb se neeche jata hai, wo increasingly concentrated hota hai, aur ascending limb me jaate hi dilute ho jata hai. Ye system salts aur urea ko surrounding interstitial fluid me retain karta hai, jo allow karta hai water ko collecting duct me reabsorb hone aur concentrated urine banane me — jo initial filtrate se up to four times zyada concentrated hota hai.
Final urine temporarily urinary bladder me store hota hai, aur jab full ho jata hai, signal central nervous system (CNS) ko jata hai micturition (urine release) initiate karne ke liye, urethral sphincter relax karte hue aur bladder muscles contract karte hue. Kidneys ke alawa, skin, lungs, aur liver bhi excretion me contribute karte hain. Lungs CO₂ aur water vapour remove karte hain, liver waste bile ke through eliminate karta hai, aur skin salts, urea, aur water sweat aur sebum ke through excrete karta hai.
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