Questions: Excretory Products and their Elimination

Q1. What are the main nitrogenous wastes of animals?

Answer (English): The main nitrogenous wastes are ammonia, urea and uric acid, and animals also get rid of carbon dioxide and water. Ammonia is very soluble and very toxic, urea is less toxic, and uric acid is the least soluble and can be excreted as a semi-solid. The form used depends mainly on the habitat and the water available to the animal.

Hinglish: Main nitrogenous wastes ammonia, urea aur uric acid hain; ammonia sabse toxic aur uric acid sabse kam soluble hai, aur animal ka habitat decide karta hai ki kaunsa waste use hoga.

Q2. Distinguish ammonotelism, ureotelism and uricotelism.

Answer (English): Ammonotelism is the excretion of ammonia, and it is seen in bony fishes, aquatic amphibians and aquatic insects that live with plenty of water. Ureotelism is the excretion of urea, and it is seen in mammals, many amphibians and marine fishes, where the liver converts ammonia into urea. Uricotelism is the excretion of uric acid, and it is seen in birds, reptiles and land snails, where water conservation is important.

Hinglish: Ammonotelism mein ammonia, ureotelism mein urea aur uricotelism mein uric acid nikalta hai. Ammonotelism paani wale animals mein, ureotelism mammals aur amphibians mein, aur uricotelism birds aur reptiles mein hota hai.

Q3. Name the excretory structures of flatworm, earthworm, cockroach and prawn.

Answer (English): A flatworm has protonephridia with flame cells, an earthworm has nephridia, a cockroach has Malpighian tubules, and a prawn has antennal glands or green glands. These structures remove nitrogenous wastes and also help in ionic and fluid balance.

Hinglish: Flatworm mein flame cells, earthworm mein nephridia, cockroach mein Malpighian tubules aur prawn mein green glands excretory structures hain.

Q4. Name the parts of the human urinary system.

Answer (English): It is made of two kidneys, two ureters, one urinary bladder and one urethra. The kidneys form the urine, the ureters carry it to the bladder, the bladder stores it, and the urethra releases it from the body.

Hinglish: Human urinary system mein kidneys, ureters, urinary bladder aur urethra hain; kidneys urine banati hain, ureters use bladder tak le jate hain aur urethra use bahar nikalta hai.

Q5. Draw and label the parts of a nephron.

Answer (English): A nephron has a glomerulus enclosed by Bowman's capsule, which together form the malpighian body. From the capsule the tubule continues as the proximal convoluted tubule, then the descending and ascending limbs of the loop of Henle, then the distal convoluted tubule, and finally the collecting duct. The afferent arteriole brings blood in, the efferent arteriole takes it out, and the peritubular capillaries and vasa recta surround the tubule.

Hinglish: Nephron mein glomerulus aur Bowman's capsule, PCT, Henle's loop ke descending aur ascending limbs, DCT aur collecting duct hote hain, aur blood afferent arteriole se aakar efferent se nikalta hai.

Q6. What are the three processes of urine formation?

Answer (English): Urine is formed by glomerular filtration, tubular reabsorption and tubular secretion. Filtration pushes the plasma through the glomerular membrane into Bowman's capsule and keeps the proteins back. Reabsorption takes useful substances such as glucose, amino acids, sodium and water back into the blood. Secretion adds hydrogen ions, potassium ions and ammonia to the tubular fluid, which adjusts the ionic and acid base balance.

Hinglish: Urine formation ke teen steps filtration, reabsorption aur secretion hain; filtration plasma ko Bowman's capsule mein bhejta hai, reabsorption useful substances wapas blood mein laata hai aur secretion H+, K+ aur ammonia ko filtrate mein dalti hai.

Q7. Define GFR and explain how it is regulated.

Answer (English): The glomerular filtration rate is the volume of filtrate formed by both kidneys in one minute, about 125 mL per minute or 180 litres per day in a healthy adult. It is regulated by the juxtaglomerular apparatus. A fall in the glomerular blood flow or pressure makes the JG cells release renin, and the renin-angiotensin-aldosterone mechanism constricts the vessels, raises the blood pressure and brings the GFR back to normal.

Hinglish: GFR ek minute mein bane filtrate ka volume hai, healthy adult mein lagbhag 125 mL/min ya 180 litre/day. Isse JGA regulate karta hai: GFR girne par renin nikalti hai aur renin-angiotensin-aldosterone system pressure badhakar GFR wapas normal karta hai.

Q8. What is the role of the PCT, DCT and collecting duct?

Answer (English): The PCT reabsorbs nearly all the nutrients and about 70 to 80 per cent of the electrolytes and water, and it keeps the pH in order by secreting hydrogen ions and ammonia and absorbing bicarbonate. The DCT makes a conditional reabsorption of sodium and water and also secretes hydrogen and potassium ions and ammonia. The collecting duct reabsorbs large amounts of water so that concentrated urine can be formed, lets urea pass into the medulla, and adjusts pH and ionic balance.

Hinglish: PCT bulk reabsorption aur pH balance karta hai, DCT conditional Na+ aur paani reabsorb karta hai, aur collecting duct paani reabsorb karke urine concentrate karta hai aur urea medulla mein bhejta hai.

Q9. Explain the counter current mechanism.

Answer (English): The loop of Henle and the vasa recta run side by side, and the fluid in their two limbs flows in opposite directions, so two counter currents operate together. The ascending limb of the loop pumps sodium chloride into the medullary interstitium, and the descending limb is permeable to water. The vasa recta carry the water away without removing the salt and urea. The result is an osmolarity gradient that rises from about 300 mOsmol per litre in the cortex to about 1200 in the inner medulla, and this hypertonic medulla lets the collecting duct reabsorb water and concentrate the urine.

Hinglish: Loop of Henle aur vasa recta ke dono limbs opposite directions mein flow karte hain. Ascending limb NaCl medulla mein bhejta hai aur descending limb paani ke liye permeable hai, isse 300 se 1200 mOsmol/L ka gradient banta hai jo collecting duct se paani nikal kar urine concentrate karta hai.

Q10. How is kidney function regulated and how is urine released?

Answer (English): ADH from the neurohypophysis increases water reabsorption in the later tubule when the body loses fluid. A fall in GFR makes the JG cells release renin, which through angiotensin II and aldosterone raises the blood pressure, the sodium reabsorption and the GFR. ANF from the heart lowers the blood pressure and brakes the renin-angiotensin mechanism. Urine is released by the micturition reflex, in which stretch receptors of a full bladder signal the central nervous system, and motor messages contract the bladder and relax the urethral sphincter.

Hinglish: ADH paani reabsorb karta hai, renin-angiotensin-aldosterone GFR aur Na+ reabsorption badhata hai aur ANF brake lagata hai. Urine micturition reflex se release hoti hai jisme bladder ke stretch receptors CNS ko signal bhejte hain aur bladder contract hokar sphincter relax ho jata hai.

Quiz pointer. A five question chapter quiz follows this page. Attempt it without looking back and read the explanation for every question you miss, because the quiz retests the nitrogenous wastes, the tubules and the counter current numbers.