Excretory Products and their elimination Sample paper

Q1. The following substances are the excretory products in animals. Choose the least toxic from among them.  

  • 1) Carbon dioxide  
  • 2) Ammonia  
  • 3) Urea  
  • 4) Uric acid  

Solution

The toxicity of excretory products is as follows:     Ammonia ˃ Urea ˃ Uric acid      Carbon dioxide is a respiratory product and is eliminated through diffusion from the body.   

Q2. The kidney of an adult frog is

  • 1) Pronephros
  • 2) Mesonephros
  • 3) Opisthonephros
  • 4) Metanephros

Solution

A mesonephric kidney consists of a large number of tubules which develop internal glomeruli enclosed in capsules forming Malpighian bodies. In amphibians, it is functional in both embryo and adult.

Q3. Enteronephric nephridia of earthworms are mainly concerned with

  • 1) Osmoregulation
  • 2) Digestion
  • 3) Respiration
  • 4) Excretion of nitrogenous wastes

Solution

In annelids such as earthworms, nephridia are excretory organs. They contain septal nephridia which discharge the excretory fluid into the intestine. So, these are called enteronephric nephridia.

Q4. Where do you find the slit pores in the Bowman’s capsule?

Solution

Slit pores are present between the podocytes in Bowman’s capsule.

Q5. Name the disorder in which glucose is present in excess quantities in urine.

Solution

Glycosuria

Q6. Name any two classes of uricotelic animals of the phylum Chordata.

Solution

Reptiles and birds

Q7. The main function of Henle’s loop is  

  • 1) Conservation of water  
  • 2) Passage of urine  
  • 3) Formation of urine  
  • 4) Filtration of blood  

Solution

The main function of Henle’s loop is to reabsorb water and important nutrients in the filtrate. Through the counter-current mechanism, it aims to reduce the volume of water and solutes within the urine without any change in its concentration.  

Q8. Haematuria means

  • 1) None of the above
  • 2) WBCs in urine
  • 3) RBCs in urine
  • 4) Both 1 and 2 above

Solution

Haematuria means the presence of red blood cells (erythrocytes) in the urine.

Q9. State the condition in which urea gets accumulated in the blood.

Solution

Uraemia

Q10. Distinguish between ammonotelism and ureotelism.

Solution

Ammonotelism Ureotelism Waste products are excreted in the form of ammonia. Waste products are excreted in the form of urea. Elimination of ammonia requires more water. Elimination of uric acid requires moderate amount of water. Ammonia is highly toxic. Urea is less toxic than ammonia. Aquatic amphibians, bony fish and aquatic insects exhibit ammonotelism. Marine fish, mammals and terrestrial amphibians exhibit ureotelism.  

Q11. The liquid which collects in the cavity of Bowman’s capsule is

  • 1) Concentrated urine
  • 2) Urea, glycogen and water
  • 3) Blood plasma minus proteins
  • 4) Glycogen and water

Solution

The glomerular filtrate which collects in the Bowman’s capsule contains only corpuscles and plasma proteins. The filtrate is protein-free and cell-free plasma in composition and osmotic pressure.

Q12. If kidneys fail to reabsorb water, the effect on tissue would

  • 1) take more oxygen from blood
  • 2) shrink and shrivel
  • 3) remain unaffected
  • 4) absorb water from blood plasma

Solution

If kidney fails to reabsorb water, the concentration of urine will be low and urination will be more frequent. This condition is called polyuria. In this condition, the tissues of the body will be dehydrated and shrink.

Q13. Name the excretory organs found in the following organisms: Earthworm Liver fluke Prawns Cockroach

Solution

Animal Excretory Organs Earthworm Nephridia Liver fluke Flame cells Prawns Green/antennal glands Cockroach Malpighian tubules  

Q14. Name the largest gland of the human body.

Solution

Liver

Q15. The yellow colour of urine is due to

  • 1) Urochrome
  • 2) Uric acid
  • 3) Bilirubin
  • 4) Urea

Solution

The yellow colour of urine is due to the pigment urochrome derived from the breakdown of haemoglobin from worn-out RBCs.  

Q16. The condition of failure of the kidney to form urine is called

  • 1) None of the above
  • 2) Anuria
  • 3) Entropy
  • 4) Deamination

Solution

The condition of failure of the kidney to form urine is called anuria.

Q17. What is uraemia? Name and describe the process used to remove waste substances from individuals suffering from uraemia.

Solution

Uraemia is the accumulation of urea in the blood due to malfunctioning of the kidneys. In individuals suffering from uraemia, the waste substances are removed by haemodialysis. In this process, blood is drained from the convenient artery (usually radial artery), mixed with anticoagulant such as heparin and pumped into the dialysing unit. The dialysing unit consists of a coiled tube surrounded by a dialysing fluid.

The dialysing unit has the same composition as that of the plasma membrane, but it does not contain any nitrogenous waste. The absence of nitrogenous water in the dialysing unit enables the easy movement of waste from urine into the tube through the porous membrane, thus clearing the blood from any waste. The cleared blood is then pumped back into the body through the same vein after adding anti-heparin.

Q18. State the type of epithelium which lines the inner wall of PCT.

Solution

Simple cuboidal brush border epithelium

Q19. Explain micturition.

Solution

The process of release of urine is called micturition. When the urinary bladder gets filled with urine, the stretch receptors present on the walls of the bladder send signals to the central nervous system (CNS). In response to these signals, CNS sends the motor message which causes the contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincters. This results in the release of urine from the body.

Q20. Different organs perform the role of excretory organs in different animals.     Give the names of such two excretory organs and the names of animals in which these organs are found.   Explain the role of the excretory organ of the cockroach in detail.   What value do you learn from (a)?  

Solution

Planaria   Flame cells     Amphioxus   Protonephridia     Earthworm   Nephridia     Antennal glands Prawns     Cockroach   Malpighian tubules Malpighian tubules in cockroaches remove the nitrogenous waste products and also maintain the ionic and fluid balance in the body.  

Although there are different organs in different animals, they perform the same function. Similarly, there are human beings of different caste and religion. We must not forget that all are equal, and we should treat every person equally well.      

Q21. State the role of the distal convoluted tubule in urine formation.  

Solution

The distal convoluted tubule (DCT) is responsible for the absorption of HCO3 ions and the secretion of H+ ions, K+ ions and ammonia to maintain the pH of urine and the sodium-potassium balance in the blood.     DCT is also responsible for the conditional reabsorption of sodium ions and water.  

Q22. Animals which excrete urea produced during metabolism of amino acids are 

  • 1) Ammonotelic
  • 2) Ureotelic
  • 3) Uricotelic
  • 4) Aminotelic

Solution

Ureotelic animals – Excrete urea. Example: Amphibians Uricotelic animals – Excrete uric acid. Examples: Reptiles and insects Ammonotelic animals – Excrete ammonia. Example: Bony fish  Aminotelic animals – Excrete excess of amino acids. Examples: Molluscs and echinoderms 

Q23. What is ketonuria?

Solution

Ketonuria is a disorder in which ketone bodies are observed in the urine. It is an indication of diabetes.

Q24. State the role of Henle’s loop in urine formation.

Solution

Henle’s loop maintains high osmolarity of the medullary interstitial fluid.

Q25. Name the neural mechanism responsible for micturition.  

Solution

Micturition reflex  

Q26. A patient suffering from cholera is given saline drip because

  • 1) Na+ ions help to retain water in the body
  • 2) Cl− ions are an important component of blood plasma
  • 3) Na+ ions are important in the transport of substances across membranes
  • 4) Cl− ions help in the formation of HCl in the stomach for digestion

Solution

The cholera toxin from Vibrio cholerae causes a series of metabolic reactions—continuous activation of adenylate cyclase of intestinal epithelial cells. The high concentration of c-AMP triggers continual secretions of Cl−, HCO3− and water into the lumen of the intestine. Administration of saline not only supports the Na-K pump through which water in the cell is restored, but glucose is also symported along with sodium.

Q27. In Hydra, waste material of food digestion and nitrogenous waste material are removed from

  • 1) Mouth and body wall
  • 2) Mouth and mouth
  • 3) Body wall and body wall
  • 4) Mouth and tentacles

Solution

In Hydra, undigested residues are egested from the coelenteron through the mouth, while ammonia is removed through the general body surface.

Q28. Name the part of the nephron which is situated in the medulla of the kidney.

Solution

Henle’s loop

Q29. Distinguish between ammonotelism and uricotelism.

Solution

Ammonotelism Uricotelism Waste products are excreted in the form of ammonia. Waste products are excreted in the form of uric acid. Elimination of ammonia requires more water. Elimination of uric acid requires less amount of water. Aquatic amphibians, bony fish and aquatic insects exhibit ammonotelism. Reptiles, birds, insects and land snails exhibit uricotelism.  

Q30. Which one of the following options shows a correct matching pair?  

  • 1) Man – Ureotelic  
  • 2) Fish – Uricotelic  
  • 3) Frog – Uricotelic  
  • 4) Birds – Ammonotelic  

Solution

Man – Ureotelic       Birds – Uricotelic      Fish – Ammonotelic      Frog – Ureotelic   

Q31. State the osmolarity of the filtrate in the cortex of the kidney.

Solution

300 mOsmoiL−1

Q32. Solenocytes are the main excretory structures in

  • 1) Echinoderms
  • 2) Annelids
  • 3) Platyhelminthes
  • 4) Molluscs

Solution

Solenocytes are meant for excretion and osmoregulation in Platyhelminthes.   Annelids have metanephridia for excretion. Molluscs have kidneys for excretion. Echinoderms possess no excretory organs as excretion occurs by osmosis or diffusion.

Q33. What is the GFR of a healthy individual?  

Solution

GFR (i.e. the glomerular filtration rate) of a healthy individual is 125 ml/minute, i.e. 180 litres/day.  

Q34. What is the juxtaglomerular apparatus?

Solution

The juxtaglomerular apparatus is a sensitive region which is formed due to the cellular modifications in the distal convoluted tubule and the afferent arteriole at the region of their contact.

Q35. When a fresh water protozoan possessing a contractile vacuole is placed in a glass containing marine water, the vacuole will

  • 1) Increase in number
  • 2) Decrease in size
  • 3) Disappear
  • 4) Increase in size

Solution

When freshwater protozoa are placed in marine water (hypertonic), the contractile vacuoles disappear because of the absence of endosmosis. So, water does not enter the protoplasm.

Q36. The proximal convoluted tubule (PCT) is lined with  

  • 1) Cuboidal epithelium  
  • 2) Columnar epithelium  
  • 3) Simple cuboidal brush border epithelium  
  • 4) Simple ciliated brush border epithelium  

Solution

The walls of the proximal convoluted tubule (PCT) consist of a single layer of simple cuboidal cells bearing microvilli on their surface and resting on a basement membrane.  

Q37. Name the notch present on the inner concave surface of the kidney.  

Solution

Hilum  

Q38. A parrot and a dog were fed only a protein-rich diet. In what forms would they excrete nitrogenous wastes?

Solution

The parrot will excrete uric acid, while the dog will excrete urea.

Q39. In protozoa such as Amoeba and Paramecium, an osmoregulatory organelle is

  • 1) Nucleus
  • 2) Food vacuole
  • 3) Mitochondrion
  • 4) Contractile vacuole

Solution

Amoeba and Paramecium use the contractile vacuole for excretion. These are freshwater animals (hypotonic solution). Water flows from the outside to the inside of the body of the organism. The contractile vacuoles in these organisms collect excess water and gradually increase in size. When the vacuoles reach a critical size, they contract, squeezing out their contents through the process of diffusion.

Q40. Name any two substances which are reabsorbed in the renal tubule by active mechanisms.

Solution

Glucose and amino acids

Q41. Malpighian tubules are

  • 1) Excretory organs of insects
  • 2) Respiratory organs of insects
  • 3) Excretory organs of frogs
  • 4) Endocrine glands of insects

Solution

Insects, centipedes, millipedes and arachnids have Malpighian tubules for excretion.

Q42. Name the excretory organs in fish.

Solution

Body surface and gills

Q43. What are ammonotelic animals? Give any two examples.

Solution

Animals which excrete nitrogenous waste products in the form of ammonia are called ammonotelic animals. Examples: Bony fish, aquatic insects

Q44. Explain the counter-current mechanism.  

Solution

The flow of the glomerular filtrate in the two limbs of Henle’s loop and the vasa recta is in a counter-current pattern.     NaCl is transported by the ascending limb of Henle’s loop which is exchanged with the descending limb of the vasa recta.

NaCl is returned to the interstitium by the descending portion of the vasa recta.     Similarly, minute quantities of urea enter the thin segment of Henle’s loop which is transported back to the interstitium by the collecting tubule.     The counter-current pattern and the proximity between the Henle’s loop and the vasa recta help to maintain the osmolarity in the inner medullary interstitium, i.e. 300 mOsmoiL−1 in the cortex and 1200 mOsmoiL−1 in the medulla.     This process is called the counter-current mechanism.  

Q45. Name the disorder which can be diagnosed by the presence of ketone bodies in urine.

Solution

Diabetes mellitus

Q46. Name any one animal in which antennal glands act as excretory organs.

Solution

Prawns

Q47. Name the branch of the renal artery which enters the glomerulus.

Solution

Afferent arteriole

Q48. What are podocytes?

Solution

Podocytes are the epithelial cells which line the Bowman’s capsule.

Q49. Describe the structure of the Malpighian body.

Solution

The Malpighian body constitutes the glomerulus and Bowman’s capsule. The glomerulus is a tuft of blood capillaries. The afferent arteriole enters the glomerulus, while the efferent arteriole leaves the glomerulus. The Bowman’s capsule is a cup-shaped structure. The glomerulus is situated in the cup-shaped depression of the Bowman’s capsule.

Q50. State the osmolarity of the filtrate in the medulla of the kidney.  

Solution

1200 mOsmoiL−1  

Q51. What structures constitute the Malpighian body?

Solution

The glomerulus and the Bowman’s capsule constitute the Malpighian body.

Q52. Name the columns of the cortex which extends between the renal pyramids.  

Solution

Columns of Bertini  

Q53. How much blood is filtered per minute by the kidneys?

Solution

1100-1200 ml

Q54. Name the excretory organ of Planaria.

Solution

Flame cells

Q55. Name the three processes involved in urine formation.

Solution

The three processes involved in urine formation are glomerular filtration, reabsorption and secretion.

Q56. Name the functional unit of the human excretory system.

Solution

Nephron

Q57. State the function of protonephridia in amphioxus.  

Solution

Protonephridia in amphioxus maintain the ionic and fluid volume, i.e. protonephridia play an important role in osmoregulation.  

Q58. Distinguish between uricotelism and ureotelism.  

Solution

Uricotelism     Ureotelism     Waste products are excreted in the form of uric acid.   Waste products are excreted in the form of urea.   Elimination of uric acid requires less amount of water.   Elimination of uric acid requires moderate amount of water.   It is the least toxic substance.   It is a moderately toxic substance.   Reptiles, birds, insects and land snails exhibit uricotelism.   Marine fish, mammals and terrestrial amphibians exhibit ureotelism.      

Q59. Describe the criteria for kidney transplantation.

Solution

The patients with terminal renal failure  are eligible for kidney transplantation. The persons at risk from a life-threatening disease are not eligible for kidney transplantation. 

Q60. State the function of rennin.

Solution

Renin stimulates the glomerular blood flow to bring the glomerular filtration rate back to normal.

Q61. Name the nitrogenous waste product which requires a large amount of water for its elimination.

Solution

Ammonia

Q62. What is sweat? What does it contain? State its function.

Solution

Sweat is a watery fluid secreted by the sweat glands located in the skin. Sweat contains NaCl, urea in small amount and lactic acid. Functions of sweat: Sweat facilitates the cooling effect on the body surface. It helps to remove some excretory substances from the body such as lactic acid, urea etc.

Q63. Name the enzyme secreted by the juxtaglomerular cells.

Solution

Renin

Q64. Name a vasoconstrictor which increases the glomerular blood pressure.  

Solution

Angiotensin II  

Q65. Name the three layers through which blood is filtered during glomerular filtration.  

Solution

Layers through which blood filters during glomerular filtration are     Endothelium of glomerular blood vessels   Epithelium of Bowman’s capsule   Basement membrane present between the endothelium of the glomerulus and the epithelium of Bowman’s capsule  

Q66. Explain how the glomerular filtration rate is maintained by the kidneys?  

Solution

Maintenance of the glomerular filtration rate is carried out by the juxtaglomerular apparatus in the kidneys.     It is the region formed by the close contact between the distal convoluted tubule and the afferent arteriole at a region.     When GFR falls, it stimulates JGA to release rennin.     Renin helps to bring reduced GFR back to normal.  

Q67. Describe the internal structure of the kidney.

Solution

Internal structure of the kidney:   The kidney is a bean-shaped structure. Internally, it is divided into an outer cortex and an inner medulla. The medulla is in the form of medullary pyramids. Medullary pyramids are projected into the calyces. The cortex which extends between the medullary pyramids is called columns of Bertini.

Q68. What is vasa recta? State its function.

Solution

Vasa recta is the minute vessel of the peritubular network which runs parallel to the loop of Henle. It maintains the concentration gradient in the medullary interstitium and helps to maintain the osmolarity of blood.

Q69. Name the network of the efferent arteriole formed around the renal tubule.

Solution

Peritubular capillaries

Q70. State the function of sebum.

Solution

The sebum provides a protective oily covering which protects the skin.

Q71. Explain the renin-angiotensin mechanism.  

Solution

A fall in glomerular blood pressure activates the juxta glomerular cells to release renin.     Renin converts angiotensin, first to angiotensin I and then to angiotensin II.     Angiotensin II increases the glomerular blood pressure which increases the glomerular filtrate rate (GFR).

At the same time, angiotensin II activates the adrenal cortex to release aldosterone.     Aldosterone stimulates the reabsorption of sodium ions and water from DCT. This also results in an increase in GFR.  

Q72. State in one line as to what happens in following disorders: Renal calculi Glomerulonephritis

Solution

Renal calculi – An insoluble mass of crystals of oxalates is formed in the kidneys. Glomerulonephritis – Inflammation of glomeruli of the kidneys.

Q73. Name the cells which secrete K+ and H+ during urine formation.  

Solution

Tubular cells secrete K+ and H+ during urine formation.