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Class 10 SELINA Solutions Biology Chapter 9 - The Excretory System

The Excretory System Exercise Ex. 1

Solution A.1

(c) Removal of nitrogenous wastes

Solution A.2

(a) Proximal convoluted tubule

Solution A.3

(c) Sweating

Solution A.4


Solution B.1

(a) Cortex

(b) Glomerulus

(c) Distal convoluted tubule (DCT)

(d) Kidney

(e) Urethra

(f) Urochrome

Solution B.2

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

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

Solution B.3

(a) Ultrafiltration

(b) Excretion

(c) Osmoregulation

(d) Excretion

Solution B.4

Abnormal constituents


(a) Blood


(b) Glucose


(c) Albumin


(d) Bile pigments

Anaemia, hepatitis (jaundice), liver cirrhosis


Solution C.1

(a) Glomerulus is involved in 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) Henle's loop is involved in reabsorption of water and sodium ions.

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

(d) Renal artery supplied blood to the kidney.

(e) Urethra is involved in the process of micturition i.e. expelling urine out of the body.

Solution C.2

Column I

Column II 

(a)   Bowman's Capsule


(b)   Contains more CO2 and less urea

Renal Vein

(c)    Anti-diuretic hormone

Regulates amount of water excreted

(d)   Contains more urea

Renal artery

Solution C.3

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.

Solution C.4

(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. Loop of Henle

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

Solution C.5

(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.

Solution C.6

(a) PCT: Proximal Convoluted Tubule

(b) DCT: Distal Convoluted Tubule

(c) ADH: Antidiuretic hormone

(d) ORS: Oral Rehydration Solution

Solution C.7

(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.

Solution D.1

(a) Excretion: The process of removal of chemical wastes especially nitrogenous waste from the body is known as excretion.


(b) Kidney: Kidneys are primary excretory organs eliminating nitrogenous wastes mainly urea from the blood and throwing it out of the body in the form of urine.


(c) Micturition: The process of expelling urine out of the body through urethra by opening the sphincter muscles passing of urine involving relaxation of sphincter muscles between the urinary bladder and urethra is called micturition.


(d) Osmoregulation: Osmoregulation is a process of maintaining the blood composition of the body i.e. the normal osmotic concentration of water and salts in the body.

Solution D.2

(a) Differences between Bowman's capsule and Malpighian capsule (structure):

Bowman's capsule

Malpighian capsule

Bowman's capsule is a thin walled 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.


(b) Differences between diuresis and uremia (cause and problem):



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.


(c) Differences between renal cortex and renal medulla (location and appearance):

Renal cortex

Renal medulla

The renal cortex is the outer darker region of the kidney.

The renal medulla is the inner lighter region of the kidney.


(d) Differences between renal pelvis and renal papilla (structure):

Renal pelvis

Renal 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.


(e) Differences between urea and urine:



Urea is the chief excretory product which is excreted in the form of urine.

Urine is the filtrate left after reabsorption and tubular secretion which contains 95% water and 5% solid wastes.


(f) Differences between excretion and secretion (utility):



Excretion helps in the removal of chemical wastes especially nitrogenous wastes from the body.

Secretion helps in the passage of substances such as potassium and large number of foreign chemicals and drugs in the forming urine.


Solution D.3

(a) Excretion helps in removing toxic wastes from our body and it also plays an important role in osmoregulation i.e. the maintenance of homeostasis of the body. Hence, excretion is a necessary process of our body.


(b) If one kidney is donated to a needy patient, the other kidney alone is sufficient for removing wastes or excretion. Thus, the donor can live a normal life.


(c) During summer, a considerable part of water is lost through perspiration so the kidneys have to reabsorb more water from the urine. This makes the urine thicker in summer than in winters.

Solution D.4

A uriniferous tubule also known as the kidney tubule is the structural and functional unit of the kidney.

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.

Solution D.5

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.

Solution D.6


Ultrafiltration involves filtration of the blood which takes place in the glomerulus. The blood containing urea from the afferent arteriole enters the glomerulus under high pressure. The high pressure is created because 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 filtrate is known as 'glomerular filtrate'.

Glomerular filtrate consists of water, urea, salts, glucose and other plasma solutes. Blood corpuscles, proteins and other large molecules remain behind in the glomerulus. Therefore the blood which is carried away by the efferent arteriole is relatively thick.

Selective absorption

The Glomerular filtrate entering the renal tubule contains a lot of usable materials such as glucose and sodium. As this filtrate passes down the renal tubule, a lot of water along with these usable materials is reabsorbed. Such reabsorption is called 'selective absorption'. The reabsorption occurs only to the extent that the normal concentration of the blood is undisturbed.

Solution D.7

Dialysis involves the use of artificial kidney or a dialysis machine. The patient's blood is from the radial artery is led through the machine where excess salts and urea is removed. The purified blood is then 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.

Solution E.1

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

(b) 1-renal artery, 2-renal vein, 3-ureter, 4-cortex, 5-pelvis

(c) (i) 4/cortex

(ii) medulla


Solution E.2

(a) Excretory system and Circulatory system.

(b) 1-kidney, 2-renal artery, 3-ureter, 4-urinary bladder, 5-urethera

(c) Nephron

(d) Urea and ammonia

(e) Ultrafiltration and selective reabsorption

Solution E.3

(a) 4 / Glomerulus

(b) 2 / Efferent arteriole

(c) 1 / Afferent arteriole from renal artery

(d) 7 / Collecting tubule

(e) 5 / Proximal convoluted tubule with blood capillaries

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

(g) Loop of Henle

Solution E.4

(a) The process of removal of chemical wastes especially nitrogenous waste from the body is known as excretion.


(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.

Solution E.5

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.


1 - Afferent arteriole 

2 - Glomerulus

3 - Bowman's capsule

4 - Efferent arteriole


c. Urine formation occurs in two steps - ultrafiltration and reabsorption.


d. The process occurring in 2 and 3 is known as ultrafiltration.

In the glomerulus, the blood flows under high pressure because of the narrow lumen of the capillary network of the glomerulus. This forces most of the components (both waste and useable materials) of the blood out of the capillaries. This process of the filtration of blood under high pressure in the Bowman's capsule is known as ultrafiltration.

Solution E.6

(a) 1 - Collecting duct

     2 - Distal convoluted tubule (DCT)

     3 - Descending limb of loop of Henle

     4 - Bowman's capsule

(b) The diameter of the efferent arteriole is narrower than the diameter of the afferent arteriole which builds high hydrostatic pressure in the glomerulus.

(c) Efferent arteriole

(d) Two main stages of urine formation are ultrafiltration and tubular reabsorption.

(e) Henle's loop and collecting tubules

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