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Chapter 9

The Excretory System

Class 10 - Selina Concise Biology Solutions


Multiple Choice Type

(Select the most appropriate option in each case)

Question 1

Excretion primarily involves

  1. Removal of all byproducts during catabolism.
  2. Removal of byproducts during anabolism.
  3. Removal of nitrogenous wastes. ✓
  4. Throwing out excess of water.

Question 2

Maximum amount of water from the glomerular filtrate is reabsorbed in

  1. Proximal convoluted tubule. ✓
  2. Descending limb of loop of Henle.
  3. Ascending limb of loop of Henle.
  4. Distal convoluted tubule.

Question 3

Which one of the following in real sense is NOT an excretory activity?

  1. Giving out carbon dioxide.
  2. Passing out faecal matter.
  3. Sweating. ✓
  4. Removal of urea.

Question 4

In humans, urea is formed in

  1. Ureter.
  2. Liver. ✓
  3. Spleen.
  4. kidney.

Very Short Answer Type

Question 1

Name the following:

(a) The outer region of kidney containing the Bowman's capsule.

(b) The tuft of capillaries inside the Bowman's capsule.

(c) The part of kidney tubules where the term urine is first used for the fluid in it.

(d) The organ which filters urea.

(e) The organ through which urea is released outside the body of a human being.

(f) The specific pigment found in urine.

Answer

(a) Cortex

(b) Glomerulus

(c) Distal convoluted tubule (DCT)

(d) Kidney

(e) Urethra

(f) Urochrome

Question 2

Given below are two sets (a and b) of five terms each. Rewrite the terms in their correct order so as to be in logical sequence.

(a) Afferent arteriole, renal vein, secondary capillary network, glomerulus, efferent arteriole

(b) Renal artery, urethra, ureter, kidney, urinary bladder.

Answer

(a) Afferent arteriole, glomerulus, efferent arteriole, secondary capillary network, renal vein.

(b) Renal artery, kidney, ureter, urinary bladder, urethra.

Question 3

In each one of the following sets of body parts or substances or processes, pick out the one item which overall includes the remaining four.

(a) Glomerular filtrate, Bowman's capsule, ultrafiltration, glomerulus, blood plasma.

(b) Skin, liver, lungs, kidneys, excretion.

(c) ADH, water, pituitary, osmoregulation, urine.

(d) CO2, bile pigments, water, excretion, urea.

Answer

(a) Ultrafiltration

(b) Excretion

(c) Osmoregulation

(d) Excretion

Question 4

Name the diseases caused due to the following abnormal constituents in urine:

Abnormal constituentsDiseases
(a) Blood……………………….
(b) Glucose……………………….
(c) Albumin……………………….
(d) Bile pigments……………………….

Answer

Abnormal constituentsDiseases
(a) BloodHaematuria
(b) GlucoseGlycosuria
(c) AlbuminAlbuminuria
(d) Bile pigmentsAnaemia, hepatitis (jaundice), liver cirrhosis

Short Answer Type

Question 1

Write down the functional activity of the following parts:

(a) Glomerulus

(b) Collecting duct

(c) Ureter

(d) Vasa recta

(e) Urethra

Answer

(a) Glomerulus — The main function of the glomerulus is to filter plasma to produce glomerular filtrate, which passes down the length of the nephron tubule to form urine. It is concerned mainly with the process of ultrafiltration. The liquid part of the blood which is plasma including urea, salts, glucose filters out from the glomerulus into the renal tubule.

(b) Collecting duct — The collecting duct system is the final component of the kidney to influence the body's electrolyte and fluid balance. It receives the contents of many kidney tubules and pours it as urine in the pelvis of the kidney.

(c) Ureter — It carries urine to the urinary bladder by ureteral peristalsis.

(d) Vasa recta — The vasa recta is a secondary capillary network that branches out of the efferent arteriole. It consists of long, hairpin-shaped blood vessels that run parallel to the loops of Henle. The hairpin turns slow the rate of blood flow, which helps maintain the osmotic gradient required for water reabsorption.

(e) Urethra — Urine is expelled from the urinary bladder through the urethra. This process is called as micturition.

Question 2

Match the items in Column I with those in Column II and write down the matching pairs.

Column IColumn II
(a) Bowman's Capsule(i) Renal artery
(b) Contains more CO2 and less urea(ii) Regulates amount of water excreted
(c) Anti-diuretic hormone(iii) Renal vein
(d) Contains more urea(iv) Glomerulus

Answer

Column IColumn II
(a) Bowman's CapsuleGlomerulus
(b) Contains more CO2 and less ureaRenal Vein
(c) Anti-diuretic hormoneRegulates amount of water excreted
(d) Contains more ureaRenal artery

Question 3

Fill in the blanks in the following passage to make it a meaningful description.

In a nephron, the .......... flows through the .......... under great pressure. The reason for this great pressure is that the .......... (outgoing) .......... is narrower than the .......... (incoming). This high pressure causes the .......... part of the blood to filter out from the .......... into the .......... capsule.

Answer

In a nephron, the blood flows through the glomerulus under great pressure. The reason for this great pressure is that the efferent (outgoing) arteriole is narrower than the afferent arteriole (incoming). This high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal capsule.

Question 4(a)

Name the following:

Three nitrogenous wastes of our body.

Answer

Three nitrogenous wastes of our body:

  1. Urea
  2. Uric acid
  3. Ammonia

Question 4(b)

Name the following:

Three organic wastes of our body.

Answer

Three organic wastes of our body:

  1. Urea
  2. Uric acid
  3. Creatinine

Question 4(c)

Name the following:

Three inorganic wastes of our body.

Answer

Three inorganic wastes of our body:

  1. Common salt (NaCl)
  2. Iron
  3. Calcium

Question 4(d)

Name the following:

Three main parts of our urinary system.

Answer

Three main parts of our urinary system:

  1. Kidney
  2. Urinary bladder
  3. Ureter

Question 4(e)

Name the following:

Six main parts of nephron.

Answer

Six main parts of nephron:

  1. Bowman's capsule
  2. Glomerulus
  3. Renal capsule
  4. Proximal convoluted tubule (PCT)
  5. Henle's Loop
  6. Distal convoluted tubule (DCT)

Question 4(f)

Name the following:

Three stages of urine formation.

Answer

Three stages of urine formation:

  1. Ultrafiltration
  2. Reabsorption
  3. Tubular secretion

Question 4(g)

Name the following:

Three types of fluids in different parts of a nephron.

Answer

Three types of fluids in different parts of a nephron:

  1. Glomerular filtrate
  2. Glomerular filtrate with glucose and sodium
  3. Urine

Question 5

Choose the odd one out in each of the following sets and write the category for the remaining terms:

(a) Kidney, ureter, neuron, urethra, urinary bladder

(b) Ammonia, urea, excess sodium chloride, uric acid

(c) Cortex, medulla, loop of Henle, hilum

(d) Glomerulus, collecting duct, papilla, Bowman's capsule.

Answer

(a) Odd term: Neuron
Category: Others are parts of the human excretory system.

(b) Odd term: Excess sodium chloride
Category: Others are organic nitrogenous wastes.

(c) Odd term: Loop of Henle
Category: Others are parts of the internal structure of kidney.

(d) Odd term: Papilla
Category: Others are parts of the kidney tubule or nephron.

Question 6

Write full forms of the following abbreviations:

(a) PCT: ……………………….

(b) DCT: ……………………….

(c) ADH: ……………………….

(d) ORS: ……………………….

Answer

(a) PCT — Proximal Convoluted Tubule

(b) DCT — Distal Convoluted Tubule

(c) ADH — Antidiuretic hormone

(d) ORS — Oral Rehydration Solution

Question 7

Write the exact location of each of the following:

(a) Kidney

(b) Uriniferous tubule

(c) Malpighian capsule

(d) Loop of Henle

Answer

(a) Kidney — It is located on either side of the backbone and protected by the last two ribs.

(b) Uriniferous tubule — Uriniferous tubule begins in the cortex; the tubule dips down to the medulla, then return to the cortex before draining into the collecting duct.

(c) Malpighian capsule — It comprises of Bowman's capsule and glomerulus and is located in the kidney tubule.

(d) Loop of Henle — It runs in the medulla to turn back and to re-enter the cortex to continue into the next convoluted region of the tubule.

Descriptive Type

Question 1

Define the following terms:

(a) Excretion

(b) Kidney

(c) Micturition

(d) Osmoregulation

Answer

(a) Excretion — Excretion is the passing out of substances that have no further use in the body or are harmful.

(b) Kidney — The kidneys are a pair of organs that are found on either side of the spine, just below the rib cage in the back. The Kidneys are powerful chemical factories that perform the following function of removing waste products from the body, filter waste materials out of the blood and pass them out of the body as urine. It also regulates blood pressure and the levels of water, salts and minerals in the body.

(c) Micturition — Urine is expelled from the urinary bladder through the urethra by relaxation of the sphincter muscles located at the opening of the urinary bladder into the urethra under impulse from the nervous system. This process is called micturition.

(d) Osmoregulation — The kidney while removing wastes like urea from the blood also regulates its composition, i.e., the percentage of water and salts. This function is called osmoregulation – it implies the regulation of osmotic pressure of the blood.

Question 2(a)

Differentiate between the following pairs of terms:

Bowman's capsule and Malpighian capsule (structure)

Answer

Difference between Bowman's capsule and Malpighian capsule with reference to their structure is:

Bowman's capsuleMalpighian capsule
Bowman's capsule is a thin walled (single-cell thick epithelium) cup, containing the glomerulus.The Bowman's capsule along with the knot-like mass of blood capillaries called glomerulus together are known as malpighian capsule.

Question 2(b)

Differentiate between the following pairs of terms:

Diuresis and Uremia (cause and problem)

Answer

Difference between Diuresis and Uremia (cause and problem):

DiuresisUremia
Diuresis results in increased production of urine due to less secretion of ADH.Uremia is the accumulation of high quantities of urea in blood due to inability of the kidneys to filter out wastes.

Question 2(c)

Differentiate between the following pairs of terms:

Renal cortex and Renal medulla (location and appearance)

Answer

Difference between Renal cortex and Renal medulla (location and appearance):

Renal cortexRenal medulla
The renal cortex is the outer darker region of the kidney.The renal medulla is the inner lighter region of the kidney.

Question 2(d)

Differentiate between the following pairs of terms:

Renal pelvis and Renal papilla (structure)

Answer

Difference between Renal pelvis and Renal papilla (structure):

Renal pelvisRenal papilla
The renal pelvis is the expanded front end of the ureter in the kidney.The renal papilla is the apex of the renal pyramid which projects into the pelvis.

Question 2(e)

Differentiate between the following pairs of terms:

Urea and urine

Answer

Difference between Urea and Urine:

UreaUrine
Urea is a chemical compound and is first produced in liver through the metabolism of nucleic acids and amino acids. Urea is the chief excretory product which is excreted in the form of urine.The filtrate left after reabsorption and tubular secretion which contains 95% water and 5% solid wastes.

Question 2(f)

Differentiate between the following pairs of terms:

Excretion and secretion (utility)

Answer

Difference between Excretion and Secretion (utility):

ExcretionSecretion
Excretion is the passing out of substances that have no further use in the body or are harmful.Secretion is giving out by a cell or a gland some substance that has some utility for the body.

Question 3(a)

Give reason/explain:

Excretion is a necessary process of our body.

Answer

Living creatures excrete themselves. It is necessary to eliminate certain waste and toxic products, such as carbon dioxide, urea etc. When these toxic materials are not removed from the body, they get mixed with blood and can cause poisoning that slows down critical chemical reactions and damage the cells of the body. Hence it is necessary to remove such poisonous waste materials from our body.

Question 3(b)

Give reason/explain:

If we donate one kidney to a needy patient, would it cause any harm to us.

Answer

If one kidney is donated to a needy patient, the other kidney alone is sufficient for excretory needs and the person can lead a normal life.

Question 3(c)

Give reason/explain:

We urinate fewer times in summer than in winter and the urine passed is generally thicker.

Answer

During summer when the surrounding temperature is high, we lose a considerable part of water through perspiration (i.e., in the form of sweat, direct evaporation, etc.). This means that the kidneys have to reabsorb more water from the urine. Due to this reason, we urinate fewer times in summer than in winter and the urine passed is generally thicker.

Question 4

What is a uriniferous tubule? How does it function?

Answer

The structural and functional unit of the kidney is the uriniferous tubule. The kidney is composed of an enormous number of minute tubules called uriniferous tubules or nephrons or renal tubules.
It takes in impure blood from the renal artery and removes wastes in the form of urine. It also provides a larger surface area for reabsorption of salts and water.

Question 5

Why is it necessary to maintain a normal osmotic concentration of the blood?

Answer

Maintaining a normal osmotic concentration in the body means regulating the percentage of water and salts. If this regulation mechanism fails we either end up losing vital salts and water or may accumulate unwanted salts and excess water in our body.

Question 6

Explain the terms ultrafiltration and selective absorption.

Answer

Ultrafiltration — The blood flows through the glomerulus under great pressure which is much greater than in the capillaries elsewhere. The reason for this greater pressure is that the efferent arteriole is narrower than the afferent arteriole. The high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule. This filtration under extraordinary force is called Ultrafiltration.

Selective Absorption
The glomerular filtrate entering the renal tubule is an extremely dilute solution containing a lot of useful materials such as glucose and some salts such as those of sodium. As this filtrate passes down the renal tubule, a lot of water along with these usable materials is reabsorbed. But their reabsorption is only to the extent that the normal concentration of the blood is not disturbed. This is called Selective Absorption.

Question 7

What is dialysis? Under what conditions is it carried out?

Answer

Dialysis involves the use of artificial kidney or a dialysis machine. The patient's blood is led from the radial artery in his arm through the machine where urea and excess salts are removed and the purified blood is returned to a vein in the same arm.

Dialysis is carried out in case of failure of both the kidneys. In case there is a permanent damage, then the dialysis is to be repeated for about 12 hours twice a week.

Structured / Application / Skill Type

Question 1

Look at the figure given below. It is a section of human kidney as seen from the front.

Look at the figure given below. It is a section of human kidney as seen from the front. Is it a longitudinal section or a cross-section? Name the parts numbered 1-5. Which area/part (give its name or the number given on the diagram) contains the following respectively: Malpighian capsule. The blood vessel with least/no nitrogenous waste. Freshly collected urine. Excretory System, Concise Biology Solutions ICSE Class 10.

(a) Is it a longitudinal section or a cross-section?

(b) Name the parts numbered 1-5.

(c) Which area/part (give its name or the number given on the diagram) contains the following respectively:

  1. Malpighian capsule.
  2. The blood vessel with least/no nitrogenous waste.
  3. Freshly collected urine.

Answer

(a) It is a longitudinal section of the kidney.

(b) The parts numbered 1-5 are:

  • 1 → Renal Artery
  • 2 → Renal Vein
  • 3 → Ureter
  • 4 → Cortex
  • 5 → Pelvis

(c) Given below is the area/part containing the mentioned structure:

  1. Cortex (4)
  2. Medulla
  3. Pelvis (5)

Question 2

Given alongside is the figure of certain organs and associated parts in the human body. Study the same and answer the questions that follow:

Given alongside is the figure of certain organs and associated parts in the human body. Study the same and answer the questions that follow. Name all the organ-systems shown completely or even partially. Name the parts numbered 1 to 5. Name the structural and functional unit of the part marked 1. Name the two main organic constituents of the fluid that flows down the part labelled 3. Name the two major steps involved in the formation of the fluid that passes down the part labelled 3. Excretory System, Concise Biology Solutions ICSE Class 10.

(a) Name all the organ-systems shown completely or even partially.

(b) Name the parts numbered 1 to 5.

(c) Name the structural and functional unit of the part marked '1'.

(d) Name the two main organic constituents of the fluid that flows down the part labelled '3'.

(e) Name the two major steps involved in the formation of the fluid that passes down the part labelled '3'.

Answer

(a) Excretory system and Circulatory system.

(b) The parts numbered 1-5 are:

  • 1 → Kidney
  • 2 → Renal Artery
  • 3 → Ureter
  • 4 → Urinary Bladder
  • 5 → Urethera

(c) Nephron

(d) Urea and Ammonia

(e) Ultrafiltration and Selective Absorption

Question 3

The following diagram represents a mammalian kidney tubule (nephron) and its blood supply.

The diagram represents a mammalian kidney tubule (nephron) and its blood supply. Study the diagram and answer the questions that follow: Where does ultrafiltration take place? Which structure contains the lowest concentration of urea? Which structure contains the highest concentration of urea? Which structure (normally) contains the lowest concentration of glucose? Where is most water reabsorbed? State the reason for the high hydrostatic pressure in the glomerulus. Name the part of the nephron which lies in the renal medulla. Excretory System, Concise Biology Solutions ICSE Class 10.

Parts indicated by the guidelines 1 to 8 are as follows:

  1. Afferent arteriole from renal artery
  2. Efferent arteriole
  3. Bowman's capsule
  4. Glomerulus
  5. Proximal convoluted tubule with blood capillaries
  6. Distal convoluted tubule with blood capillaries
  7. Collecting tubule
  8. U-shaped loop of Henle

Study the diagram and answer the questions that follow:

(a) Where does ultrafiltration take place?

(b) Which structure contains the lowest concentration of urea?

(c) Which structure contains the highest concentration of urea?

(d) Which structure (normally) contains the lowest concentration of glucose?

(e) Where is most water reabsorbed?

(f) State the reason for the high hydrostatic pressure in the glomerulus.

(g) Name the part of the nephron which lies in the renal medulla.

Answer

(a) Ultrafiltration takes place in Glomerulus (marked as 4 in the diagram).

(b) Efferent arteriole (marked as 2 in the diagram) contains the lowest concentration of urea.

(c) Afferent arteriole (marked as 1 in the diagram) from renal artery contains the highest concentration of urea.

(d) Collecting tubule (marked as 7 in the diagram) contains the lowest concentration of glucose.

(e) Most water is reabsorbed in Proximal convoluted tubule with blood capillaries (marked as 5 in the diagram).

(f) The efferent arteriole is narrower than the afferent arteriole. This creates a high hydrostatic pressure in the glomerulus.

(g) Loop of Henle is the part of the nephron which lies in the renal medulla.

Question 4

Given alongside is a simplified diagram of the human kidney cut open longitudinally. Answer the questions that follow:

Given is a simplified diagram of the human kidney cut open longitudinally. Answer the questions that follow. Define excretion. Why does the cortex of the kidney show a dotted appearance? Why does the medulla of the kidney show a striped appearance? Write two differences in composition of the blood flowing through the blood vessels A and B. Excretory System, Concise Biology Solutions ICSE Class 10.

(a) Define excretion.

(b) Why does the cortex of the kidney show a dotted appearance?

(c) Why does the medulla of the kidney show a striped appearance?

(d) Write two differences in composition of the blood flowing through the blood vessels, 'A' and 'B'.

Answer

(a) Excretion is the removal of harmful and unwanted nitrogenous waste products from the body.

(b) As the cortex region contains numerous nephrons or kidney tubules, therefore, it shows a dotted appearance.

(c) As the medulla region contains several conical pyramids, therefore, it shows a striped appearance.

(d) The blood vessel 'B' is renal artery and the blood vessel 'A' is renal vein. So the blood vessel 'B' contains oxygenated blood with high concentration of urea and glucose whereas the blood vessel 'A' contains deoxygenated blood with low concentration of urea and glucose as compared to renal artery.

Question 5

Study the diagram given alongside and then answer the questions that follow:

Study the diagram and answer the questions that follow. Name the region in the kidney where the above structure is present? Name the parts labelled 1, 2, 3, and 4. Name the stages involved in the formation of urine. What is the technical term given to the process occurring in 2 and 3? Briefly describe the process. Excretory System, Concise Biology Solutions ICSE Class 10.

(a) Name the region in the kidney where the above structure is present?

(b) Name the parts labelled 1, 2, 3, and 4.

(c) Name the stages involved in the formation of urine.

(d) What is the technical term given to the process occurring in 2 and 3? Briefly describe the process.

Answer

(a) The structure is a Bowman's capsule, which is part of the nephron. The Bowman's capsule is found in the cortex of the kidney.

(b) The parts labelled 1-4 are:

  • 1 → Afferent arteriole
  • 2 → Glomerulus
  • 3 → Bowman's capsule
  • 4 → Efferent arteriole

(c) Urine formation occurs in three major steps:

  1. Ultrafiltration
  2. Reabsorption
  3. Tubular Secretion.

(d) The process occurring in 2 and 3 is known as Ultrafiltration.
The blood flows through the glomerulus under great pressure which is much greater than in the capillaries elsewhere. The reason for this greater pressure is that the efferent arteriole is narrower than the afferent arteriole. The high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule. This filtration under extraordinary force is called Ultrafiltration.

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