The Excretory System

Progress Check 1

Question 1

Given below is a list of substances — select the ones that need to be eliminated from the body.

Glucose, excess water, amino acids, urea, carbon dioxide, excess common salt, glycogen, uric acid

Answer

excess water, urea, carbon dioxide, excess common salt, uric acid

Question 2

Give two examples of the following:

(i) Nitrogenous waste

(ii) Bile pigments

(iii) Main excretory organs

(iv) Accessory excretory organs

(v) Water-soluble vitamins

Answer

(i) Urea, Uric acid

(ii) Bilirubin, Biliverdin

(iii) Kidney, Urinary bladder

(iv) Skin, Lungs

(v) Vitamin B, Vitamin C

Progress Check 2

Question 1

Name the following :

(i) The tube arising from the notch of the kidney on the median side and connecting behind with the urinary bladder.

(ii) The tube that passes the urine to the outside of the body.

(iii) The inner lighter coloured region of the kidney.

(iv) Knot-like mass of blood capillary inside Bowman's capsule.

(v) The structural and functional unit of the kidney.

(vi) The blood vessel which :

1. enters malpighian capsule
2. leaves malpighian capsule

Answer

(i) Ureter

(ii) Urethra

(iii) Medulla

(iv) Glomerulus

(v) Nephron

(vi) (a) Afferent arteriole (b) Efferent arteriole

Question 2

Given is a jumbled list of the parts of a certain body structure — Loop of Henle, Bowman's capsule, distal convoluted tubule, glomerulus, proximal convoluted tubule.

(i) Name the structure to which the listed parts belong.

(ii) Rearrange the parts in their proper sequence from the starting point to where they end.

Answer

(i) Kidney Tubule

(ii) Glomerulus → Bowman's capsule → Proximal convoluted tubule → Loop of Henle → Distal convoluted tubule

Progress Check 3

Question 1

State if the following statements are true or false.

(i) The blood flows through glomerulus under great pressure.

(ii) Glomerular filtrate consists of many substances such as water, salts, glucose and white blood corpuscles.

(iii) Sodium chloride contained in glomerular filtrate is fully reabsorbed in the renal tubule.

(iv) The blood flowing through the renal artery is oxygenated and contains a lot of nitrogenous waste.

(v) The blood flowing through the renal vein is oxygenated and normally does not contain nitrogenous waste.

(vi) Excessive uric acid may produce kidney stones.

Answer

(i) True

(ii) False
Corrected Statement — Glomerular filtrate consists of many substances such as water, salts, glucose and plasma solutes.

(iii) False
Corrected Statement — Sodium chloride contained in glomerular filtrate is partially reabsorbed in the renal tubule.

(iv) True

(v) False
Corrected Statement — The blood flowing through the renal vein is deoxygenated and normally does not contain nitrogenous waste.

(vi) True

Multiple Choice Type

Question 1

The process of removal of unwanted metabolic wastes from the body is called :

1. Eradication
2. Emission
3. Excretion
4. Egestion

Answer

Excretion

Reason — Excretion refers to removal of all kind of wastes from the body.

Question 2

The organ that does not belong to the excretory system:

1. Urethra
2. Uterus
3. Ureter
4. Urinary bladder

Answer

Uterus

Reason — Uterus (womb) is an organ that belongs to reproductive system.

Question 3

The structural and functional unit of kidney is:

1. Neuron
2. Nerve
3. Glomerulus
4. Nephron

Answer

Nephron

Reason — Nephron is the basic structure which carries out the process of waste removal.

Question 4

Which of the following is not an example of secretion ?

1. Saliva
2. Gastric juice
3. Urine
4. Milk

Answer

Urine

Reason — Saliva, Gastric juice and Milk are secretions but urine is excretory product.

Question 5

The nephrons discharge the urine at :

1. Urinary bladder
2. Ureter
3. Renal pelvis
4. Renal pyramid

Answer

Renal pelvis

Reason — The collecting duct receives the content of nephron and pours it in renal pelvis.

Question 6

An organ that produces urea :

1. Kidney
2. Liver
3. Ureter
4. Urethra

Answer

Liver

Reason — Liver detoxifies ammonia by converting it to urea.

Question 7

The main nitrogenous waste formed in the human body :

1. Uric acid
2. Ammonia
3. Urea
4. Creatinine

Answer

Urea

Reason — The primary nitrogenous waste of the body is urea.

Question 8

The condition in which excess glucose passes with urine is termed as :

1. Glycolysis
2. Glycogenolysis
3. Glycogenesis
4. Glycosuria

Answer

Glycosuria

Reason — Glycosuria is a condition when glucose passes in the urine.

Question 9

The accumulation of high quantities of urea in the human body is termed as :

1. Diuresis
2. Dialysis
3. Uremia
4. Micturition

Answer

Uremia

Reason — Uremia is the condition of raised urea in the human body.

Question 10

The process of tubular secretion occurs in :

1. PCT
2. DPT
3. DDT
4. DCT

Answer

DCT

Reason — Tubular secretion occurs due to activity of tubular wall in Distal convoluted tubules.

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

The statements given below are false. Rewrite the correct form of the statement by changing the underlined words :

(a) The outer darker portion of the kidney is termed as medulla.

(b) The Bowman's capsule and the glomerulus together are called as renal tubule.

(c) A pair of renal arteries branch off from the vena cava and enter the kidney.

(d) The glomerular filtrate is collected in Bowman's capsule after the process of reabsorption.

(e) The pigment urochrome is the breakdown product of the haemoglobin of dead RBCs.

Answer

(a) The outer darker portion of the kidney is termed as cortex.

(b) The Bowman's capsule and the glomerulus together are called as malpighian capsule.

(c) A pair of renal arteries branch off from the aorta and enter the kidney.

(d) The glomerular filtrate is collected in Bowman's capsule after the process of ultrafiltration.

(e) The pigment bilirubin is the breakdown product of the haemoglobin of dead RBCs.

Question 4

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

Answer

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.

Answer

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

Name the following:

(a) Three nitrogenous wastes of our body.

(b) Three organic wastes of our body.

(c) Three inorganic wastes of our body.

(d) Three main parts of our urinary system.

(e) Six main parts of nephron.

(f) Three stages of urine formation.

(g) Three types of fluids in different parts of a nephron.

Answer

(a) Three nitrogenous wastes of our body:

1. Urea
2. Uric acid
3. Ammonia

(b) Three organic wastes of our body:

1. Urea
2. Uric acid
3. Creatinine

(c) Three inorganic wastes of our body:

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

(d) Three main parts of our urinary system:

1. Kidney
2. Urinary bladder
3. Ureter

(e) 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)

(f) Three stages of urine formation:

1. Ultrafiltration
2. Reabsorption
3. Tubular secretion

(g) 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 regulation of osmotic pressure of the blood by regulating its composition (water and electrolyte) is called osmoregulation.

Question 2

Differentiate between :

(a) Ureter and Urethra (function)

(b) Diabetes mellitus and Diabetes insipidus (hormones involved)

(c) Glycosuria and Albuminuria (abnormal constituents)

(d) Diuresis and Uremia (problem)

(e) Malpighian capsule and Loop of Henle (location)

Answer

(a) Difference between Ureter and Urethra (function):

(b) Difference between Diabetes mellitus and Diabetes insipidus (hormones involved):

(c) Difference between Glycosuria and Albuminuria (abnormal constituents):

(d) Difference between Diuresis and Uremia (problem):

(e) Difference between Malpighian capsule and Loop of Henle (location):

Question 3

Give reason:

(a) Excretion is a necessary process of our body.

(b) Why does the cortex of kidneys shows a 'dotted' appearance?

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

(d) Why does the medulla of kidneys shows a 'striped' appearance ?

Answer

(a) Excretion is a necessary process of our body as 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.

(b) The Bowman's capsule and the proximal convoluted part of all the nephrons lie in the cortex of kidneys giving it a 'dotted' appearance.

(c) 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.

(d) Henle's loops and collecting ducts lie in the medulla of kidneys giving it a 'striped' appearance.

Structured / Application / Skill Type

Question 1

Given below is a simple diagram of the longitudinal section of a human kidney. Study the same and answer the following questions:

(a) Name the part of kidney which is found between medulla and pelvis.

(b) What is the basic structural and functional unit of kidney ?

(c) What is main function of kidney ?

(d) Mention the exact location of kidney.

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

(f) Name the part of kidney which collects urine for the first time from the nephrons.

(g) Define 'Osmoregulation'.

(h) Name the technique which is normally suggested by the doctors to the patients in case of a permanent damage to both the kidneys.

(i) Name the hormone which is associated with the 'reabsorption' step of urine production.

(j) Draw a neat and labelled diagram of a malpighian capsule.

Answer

(a) Conical or Renal pyramids

(b) Nephron

(c) Purification of blood by extracting nitrogenous waste from the blood.

(d) Kidneys are located on either side of the backbone and protected by last two ribs.

(e) Two differences in the composition of blood flowing through blood vessels A and B:

(f) Collecting Duct

(g) The regulation of osmotic pressure of the blood by regulating its composition (water and electrolyte) is called osmoregulation.

(h) Dialysis

(i) Antidiuretic hormone (ADH)

(j) The labelled diagram of a malpighian capsule is shown below:

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:

(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 figure given below represents a kidney tubule in humans and its blood supply. Study the figure and answer the questions that follow. Write specific name and numbers shown in the diagram for each answer.

(a) Name the part which consists of a knot-like mass of blood capillaries.

(b) What is the specific name for the combination of parts shown as 5 and 3?

(c) Name the part which collects the glomerular filtrate.

(d) Where is the most water reabsorbed?

(e) Name the part which collects urine in the diagram shown.

(f) Which part lies in the medulla of the kidney?

(g) Which of the above parts is involved in the process of tubular secretion?

(h) How is hydrostatic pressure created?

(i) Where does ultrafiltration take place?

(j) Name two important constituents of urine.

Answer

(a) Glomerulus (Part 5)

(b) Malpighian Capsule

(c) Bowman's Capsule (Part 3)

(d) Proximal Convoluted Tubule (Part 2)

(e) Collecting Duct (Part 7)

(f) Loop of Henle (Part 1) & Collecting Duct (Part 7)

(g) Distal Convoluted Tubule (Part 6)

(h) The efferent arteriole is narrower than the afferent arteriole. This creates the hydrostatic pressure.

(i) Glomerulus (Part 5)

(j) Urea, Sodium chloride

Question 4

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

(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) The Bowman's capsule and the proximal convoluted part of all the nephrons lie in the cortex of kidneys giving it a dotted appearance.

(c) Henle's loops and collecting ducts lie in the medulla of kidneys giving it 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:

(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.