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#	Question	Answer
1	What are the major forms of nitrogenous wastes excreted by animals?	Ammonia, urea, and uric acid.
2	Which nitrogenous waste is the most toxic?	Ammonia.
3	Which nitrogenous waste requires a large amount of water for elimination?	Ammonia.
4	Which nitrogenous waste is the least toxic and can be excreted with minimum water loss?	Uric acid.
5	What is ammonotelism?	The process of excreting ammonia.
6	Name the animals that are ammonotelic in nature.	Many bony fishes, aquatic amphibians, and aquatic insects.
7	How is ammonia generally excreted in fishes?	By diffusion across body surfaces or through gill surfaces as ammonium ions.
8	Do kidneys play a significant role in ammonia removal in ammonotelic animals?	No, kidneys do not play any significant role.
9	What adaptation led to the production of less toxic nitrogenous wastes like urea and uric acid?	Terrestrial adaptation for conservation of water.
10	Which animals are mainly ureotelic?	Mammals, many terrestrial amphibians, and marine fishes.
11	Where is ammonia converted into urea in ureotelic animals?	In the liver.
12	Which organ filters and excretes urea from blood?	Kidneys.
13	Why is some amount of urea retained in the kidney matrix in some animals?	To maintain desired osmolarity.
14	Which animals are uricotelic?	Reptiles, birds, land snails, and insects.
15	In what form is uric acid excreted?	In the form of pellets or paste.
16	Which excretory structures are found in Platyhelminthes?	Protonephridia or flame cells.
17	What is the primary function of protonephridia?	Osmoregulation (ionic and fluid volume regulation).
18	Which excretory structures are present in earthworms and other annelids?	Nephridia.
19	What are the functions of nephridia?	Removal of nitrogenous wastes and maintenance of fluid and ionic balance.
20	Which excretory structures are found in insects including cockroaches?	Malpighian tubules.
21	What are the functions of Malpighian tubules?	Removal of nitrogenous wastes and osmoregulation.
22	Which glands perform excretory functions in crustaceans like prawns?	Antennal glands or green glands.
23	What are the components of the human excretory system?	A pair of kidneys, one pair of ureters, a urinary bladder, and a urethra.
24	Describe the shape and colour of human kidneys.	Reddish-brown and bean-shaped.
25	Between which vertebrae are kidneys situated?	Between the last thoracic and third lumbar vertebrae.
26	What is the average size of an adult human kidney?	10 - 12 cm long, 5 - 7 cm wide, and 2 - 3 cm thick.
27	What is the average weight of a human kidney?	120 - 170 g.
28	What is hilum in the kidney?	A notch on the inner concave surface through which ureter, blood vessels, and nerves enter.
29	What is the renal pelvis?	A broad funnel-shaped space inside the hilum.
30	What are calyces?	Projections of the renal pelvis.
31	Name the two zones inside the kidney.	Cortex and medulla.
32	What are medullary pyramids?	Conical masses in the medulla projecting into the calyces.
33	What are Columns of Bertini?	Renal columns formed by cortex extending between medullary pyramids.
34	What are the functional units of kidneys?	Nephrons.
35	Approximately how many nephrons are present in each kidney?	Nearly one million.
36	What are the two main parts of a nephron?	Glomerulus and renal tubule.
37	What is the glomerulus?	A tuft of capillaries formed by the afferent arteriole.
38	Which vessel carries blood away from the glomerulus?	Efferent arteriole.
39	What are Columns of Bertini?	Renal columns formed by the cortex extending between the medullary pyramids.
40	What are the functional units of the kidney?	Nephrons.
41	Approximately how many nephrons are present in each kidney?	Nearly one million.
42	What are the two main parts of a nephron?	Glomerulus and renal tubule.
43	What is the glomerulus?	A tuft of capillaries formed by the afferent arteriole.
44	Which vessel forms the glomerulus?	Afferent arteriole, a fine branch of the renal artery.
45	Which vessel carries blood away from the glomerulus?	Efferent arteriole.
46	Into which structure do the DCTs of many nephrons open?	Collecting duct.
47	Where do collecting ducts open?	Into the renal pelvis through medullary pyramids in the calyces.
48	Which parts of the nephron are located in the cortical region of the kidney?	Malpighian corpuscle, PCT, and DCT.
49	Which part of the nephron dips into the medulla?	Loop of Henle.
50	What are cortical nephrons?	Nephrons with short loops of Henle extending only slightly into the medulla.
51	What are juxta medullary nephrons?	Nephrons with very long loops of Henle running deep into the medulla.
52	What are peritubular capillaries?	Fine capillary network formed by the efferent arteriole around the renal tubule.
53	What is vasa recta?	A minute U-shaped vessel running parallel to the loop of Henle.
54	In which nephrons is vasa recta absent or highly reduced?	Cortical nephrons.
55	What are the three main processes involved in urine formation?	Glomerular filtration, reabsorption, and secretion.
56	What is the first step in urine formation?	Glomerular filtration.
57	Where does glomerular filtration occur?	In the glomerulus.
58	How much blood is filtered by the kidneys per minute on average?	1100 - 1200 mL per minute.
59	What fraction of blood pumped by each ventricle is filtered by kidneys per minute?	Roughly one-fifth.
60	Through how many layers does blood get filtered during glomerular filtration?	Three layers.
61	What are filtration slits or slit pores?	Minute spaces left between podocytes.
62	Why is glomerular filtration called ultrafiltration?	Because blood is filtered very finely through the filtration membranes.
63	What is glomerular filtration rate (GFR)?	The amount of filtrate formed by the kidneys per minute.
64	What is the normal GFR in a healthy individual?	Approximately 125 mL/minute or 180 litres/day.
65	Which structure regulates glomerular filtration rate efficiently?	Juxta glomerular apparatus (JGA).
66	What is JGA?	A special sensitive region formed by cellular modifications in the distal convoluted tubule and afferent arteriole at their contact point.
67	What happens when GFR falls?	JG cells release renin.
68	What is the role of renin released by JG cells?	It stimulates glomerular blood flow and restores GFR to normal.
69	How much filtrate is reabsorbed by renal tubules?	Nearly 99%.
70	What is reabsorption?	The process by which renal tubules absorb substances from the filtrate.
71	How are nitrogenous wastes reabsorbed?	By passive transport.
72	How does water reabsorption occur in the initial nephron segments?	Passively.
73	Why is tubular secretion important?	It helps maintain ionic and acid-base balance of body fluids.
74	What type of epithelium lines the PCT?	Simple cuboidal brush border epithelium.
75	Why does the PCT have brush border epithelium?	To increase surface area for reabsorption.
76	What percentage of electrolytes and water are reabsorbed in the PCT?	70 - 80%.
77	Which essential nutrients are reabsorbed almost completely in the PCT?	Nearly all essential nutrients.
78	Which ions are selectively secreted by the DCT?	Hydrogen ions and potassium ions.
79	What is the main function of the collecting duct regarding water balance?	Reabsorption of large amounts of water to produce concentrated urine.
80	Why does the collecting duct allow passage of small amounts of urea into the medullary interstitium?	To maintain osmolarity.
81	What is the role of the collecting duct in blood homeostasis?	Maintenance of pH and ionic balance of blood.
82	What pattern of blood flow occurs in the vasa recta?	Counter current pattern.
83	Which substances mainly create the medullary osmotic gradient?	NaCl and urea.
84	How is NaCl returned to the interstitium?	By the ascending portion of vasa recta.
85	How is urea transported back to the interstitium?	By the collecting tubule.
86	What is the main function of the counter current mechanism?	Maintenance of concentration gradient in the medullary interstitium.
87	How does the interstitial gradient help in urine concentration?	It facilitates easy passage of water from the collecting tubule.
88	How concentrated can human urine become compared to the initial filtrate?	Nearly four times more concentrated.
89	Which mechanisms regulate kidney function efficiently?	Hormonal feedback mechanisms involving hypothalamus, JGA, and heart.
90	What activates osmoreceptors in the body?	Changes in blood volume, body fluid volume, and ionic concentration.
91	Which hormone is released due to excessive loss of body fluids?	Antidiuretic hormone (ADH) or vasopressin.
92	From where is ADH released?	Neurohypophysis.
93	What is the role of ADH in the nephron?	Facilitates water reabsorption from latter parts of the tubule.
94	How does ADH prevent diuresis?	By increasing water reabsorption.
95	What happens to ADH release when body fluid volume increases?	Osmoreceptors are switched off and ADH release is suppressed.
96	How can ADH increase blood pressure?	By causing constriction of blood vessels.
97	How does increased blood pressure affect GFR?	It increases glomerular blood flow and GFR.
98	What activates JG cells to release renin?	Fall in glomerular blood flow, glomerular blood pressure, or GFR.
99	What conversion is carried out by renin?	Conversion of angiotensinogen to angiotensin I.
100	Into what is angiotensin I converted?	Angiotensin II.
101	What type of substance is angiotensin II?	A powerful vasoconstrictor.
102	How does angiotensin II affect GFR?	It increases glomerular blood pressure and GFR.
103	Which gland is activated by angiotensin II?	Adrenal cortex.
104	Which hormone is released by the adrenal cortex in this mechanism?	Aldosterone.
105	What is the combined mechanism involving renin, angiotensin, and aldosterone called?	Renin - Angiotensin mechanism.
106	Which factor is released when blood flow to atria increases?	Atrial Natriuretic Factor (ANF).
107	What is the effect of ANF on blood vessels?	Vasodilation.
108	How does ANF affect blood pressure?	It decreases blood pressure.
109	Against which mechanism does ANF act as a check?	Renin - Angiotensin mechanism.
110	What is micturition?	The process of release of urine.
111	Where is urine stored before release?	Urinary bladder.
112	What initiates the signal for micturition?	Stretching of the urinary bladder as it fills with urine.
113	Which receptors send signals to the CNS during bladder filling?	Stretch receptors present on the bladder wall.
114	What response does the CNS initiate during micturition?	Contraction of bladder smooth muscles and relaxation of urethral sphincter.
115	What is the neural mechanism causing micturition called?	Micturition reflex.
116	How much urine does an adult human excrete on average per day?	1 to 1.5 litres.
117	What is the colour of normal urine?	Light yellow.
118	What is the pH of normal urine?	Slightly acidic, around pH 6.0.
119	How much urea is excreted per day on average?	25 - 30 g.
120	What is glycosuria?	Presence of glucose in urine.
121	What is ketonuria?	Presence of ketone bodies in urine.
122	Which disease is indicated by glycosuria and ketonuria?	Diabetes mellitus.
123	Other than kidneys, which organs help in excretion?	Lungs, liver, and skin.
124	Which gland is the largest gland in the human body?	Liver.
125	Which substances are secreted in bile by the liver?	Bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins, and drugs.
126	Through what are bile pigments and other liver wastes eliminated?	Digestive wastes.
127	Which glands in the skin help in excretion?	Sweat glands and sebaceous glands.
128	What substances are present in sweat?	NaCl, small amounts of urea, lactic acid, etc.
129	What is the primary function of sweat?	To facilitate cooling effect on the body surface.
130	Which substances are eliminated by sebaceous glands?	Sterols, hydrocarbons, and waxes.
131	What is sebum?	Secretion of sebaceous glands providing oily covering to the skin.
132	Can saliva eliminate nitrogenous wastes?	Yes, small amounts.
133	What is uremia?	Accumulation of urea in blood due to kidney malfunction.
134	Why is uremia dangerous?	It may lead to kidney failure.
135	What is hemodialysis?	A process used to remove urea from blood in kidney failure patients.
136	What is the dialysing unit used in hemodialysis called?	Artificial kidney.
137	Which anticoagulant is added during haemodialysis?	Heparin.
138	What type of tube is present in the artificial kidney?	Coiled cellophane tube.
139	What is special about dialysing fluid?	It has the same composition as plasma except nitrogenous wastes.
140	How are nitrogenous wastes removed during haemodialysis?	They move out through the porous cellophane membrane along concentration gradient.
141	Through which vessel is purified blood returned to the body after dialysis?	Vein.
142	What is added before returning blood to the body after dialysis?	Anti-heparin.
143	What is the ultimate method for correction of acute renal failure?	Kidney transplantation.
144	From whom is a kidney preferably obtained for transplantation?	A close relative.
145	Why is a close relative preferred for kidney transplantation?	To minimise chances of immune rejection.
146	What are renal calculi?	Stones or insoluble masses of crystallised salts formed within the kidney.
147	What is glomerulonephritis?	Inflammation of glomeruli of the kidney.
148	What are the major nitrogenous wastes excreted by animals?	Ammonia, urea, and uric acid.
149	Name the common excretory organs found in animals.	Protonephridia, nephridia, Malpighian tubules, green glands, and kidneys.
150	What are the main functions of excretory organs?	Elimination of nitrogenous wastes and maintenance of ionic and acid-base balance.
151	What are the components of the human excretory system?	One pair of kidneys, one pair of ureters, a urinary bladder, and a urethra.
152	What is the functional unit of the kidney?	Nephron.
153	What are the two portions of a nephron?	Glomerulus and renal tubule.
154	What is the glomerulus?	A tuft of capillaries formed from afferent arterioles.
155	Where do the DCTs of many nephrons open?	Into a common collecting duct.
156	What are the three main processes involved in urine formation?	Filtration, reabsorption, and secretion.
157	What type of process is filtration in urine formation?	Non-selective process.
158	What force drives glomerular filtration?	Glomerular capillary blood pressure.
159	How much blood is filtered by the glomerulus per minute?	About 1200 mL.
160	What is the normal glomerular filtration rate (GFR)?	About 125 mL/minute.
161	Which structure regulates GFR?	Juxta Glomerular Apparatus (JGA).
162	What percentage of filtrate is reabsorbed in the nephron?	Nearly 99%.
163	Which part of the nephron is the major site of reabsorption and selective secretion?	Proximal convoluted tubule (PCT).
164	Which parts of the nephron allow extensive reabsorption of water and electrolytes?	DCT and collecting duct.
165	Which substances are retained in the kidney interstitium by the counter current mechanism?	Electrolytes and urea.
166	How much can DCT and collecting duct concentrate the filtrate?	About four times.
167	Where is urine stored before release?	Urinary bladder.
168	What is micturition?	Release of urine through the urethra.
169	Which organs assist kidneys in excretion?	Skin, lungs, and liver.
170	What is osmoregulation?	Maintenance of fluid volume and ionic balance.
171	Why are terrestrial animals generally ureotelic or uricotelic instead of ammonotelic?	To conserve water because ammonia requires large amounts of water for elimination.
172	What is the significance of JGA?	It regulates glomerular filtration rate (GFR).
173	Which chordate animal has flame cells as excretory structures?	Amphioxus.
174	What are the cortical portions between medullary pyramids called?	Columns of Bertini.
175	Which hormone facilitates water reabsorption from distal tubules?	ADH (Antidiuretic Hormone).
176	Dialysis fluid contains all plasma constituents except _______.	Nitrogenous wastes.
177	How much urea does a healthy adult excrete per day on average?	25 - 30 g/day.