Class 11 Biology NCERT Solutions for Chapter 19 – Excretory Products and their Elimination

NCERT Solutions for Class 11 Biology Chapter 19: NCERT solutions can help clear doubts if you go through them. They clearly explain complex concepts in Biology and even give questions at the end of each chapter so that students can become thorough.

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Chapter 19 in Biology for CBSE class 11 tells you about the excretory system and the elimination of waste products from the human body. It gives a gist of how the excretory system works and the distinct functions it performs.

NCERT Solutions for Class 11 Biology Chapter 19 – Excretory Products and their Elimination

 

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Chapter 19 talks about the excretory system and the by-products of excretion. As always, the solutions distribute the chapter into different sections, and each part explains one concept related to excretion.

What will you learn in NCERT Class 11 Biology Chapter 19?

Excretion is the process of removal of nitrogenous waste and other unwanted products from the body. The process is necessary to keep the insides of the body stable so that the life processes can function normally. During the process of excretion, various by-products such as ammonia, urea, and uric acid form and come out as feces.

Substances such as these accumulate through various metabolic processes that occur throughout the body. They can also form due to excessive ingestion.

The human excretory system consists of different sets of organs that help in the process. Kidneys, uterus, the urethra, and the urinary bladder are the organs that play a prominent role in excretion. Besides this, the excretory system also consists of other organs that help in excretion, including the renal artery and vein, dorsal aorta, and the pelvis, medulla, and the cortex present in the kidneys.

The kidneys have a significant role to play when it comes to the regulation of different bodily functions. For instance, they help regulate water in the body. They also help regulate arterial pressure. Besides this, kidneys help excrete waste from the body and secrete hormones like renin, which help in the regulation of renal functions.

The process of excretion occurs in three stages. In the first stage, called glomerular filtration, urine forms by the filtration of the blood. Every minute, the kidneys filter about 1100 to 1200 ml of blood. The number constitutes 20 percent of the blood that the heart pumps each minute.

Coming to the second stage, known as ‘selective reabsorption,’ the renal tube absorbs about 99 percent of the filtered blood. In this stage, water and urea get absorbed by passive transport, while sodium gets absorbed by active transport.

Similarly, other substances such as glucose and amino acids are absorbed with the help of both active and passive transport.

The last step in the formation of urine is tubular secretion. During this process, the tubules absorb certain chemicals which the glomerular capillaries do not filter out.

The urine thus formed passes through various other organs such as the Henle’s Loop, the Distal Convoluted Tube, and the Proximal Convoluted Tube, where it gets reabsorbed.

Benefits of NCERT Solutions for Biology Chapter 19

NCERT Solutions for class 11 Biology Chapter 19 comes with a host of benefits, which you can find below.

1. Practice Questions

The solutions come with hundreds of practice questions at the end of the chapter. So, students can answer them and become confident to face the exams.

2. Solved Examples

NCERT Solutions for class 11 Biology Chapter 19 in Biology also come with a set of example questions along with their solutions. Students can go through them to get a fair idea about how they should be writing their answers.

Access NCERT Solutions For Class 11 Biology Chapter 19

1. Define Glomerular Filtration Rate (GFR)

Glomerular Filtration rate (GFR) is the amount of filtrate formed by both the kidneys (nephrons) every minute. The GFR of a healthy person is approximately 125ml per minute. The GFR consists majorly of water and other constituents such as amino acids, glucose, potassium, sodium, urea, uric acid and ketone bodies.

2. Explain the autoregulatory mechanism of GFR.

Kidneys regulate the glomerular filtration rate through the mechanism which is auto regulatory. It involves the action of juxtaglomerular apparatus, which is a microscopic structure present between the returning distal convoluted tubule and vascular pole of the renal corpuscle of the same nephron. It regulates the glomerular filtration rate and renal blood flow. When the glomerular filtration rate declines, the juxtaglomerular cells are activated for the release of renin. This triggers the glomerular blood flow causing the GFR to revert to normal. Renin causes GFR to revert to normalcy by activating the renin-angiotensin mechanism.

3. Indicate whether the following statements are true or false:

(a) Micturition is carried out by a reflex.

(b) ADH helps in water elimination, making the urine hypotonic.

(c) Protein-free fluid is filtered from blood plasma into the Bowman’s capsule.

(d) Henle’s loop plays an important role in concentrating the urine.

(e) Glucose is actively reabsorbed in the proximal convoluted tubule.

(a) Micturition is carried out by a reflex – True

(b) ADH helps in water elimination, making the urine hypotonic – False

ADH helps in reabsorption of water causing the urine to be hypotonic.

(c) Protein-free fluid is filtered from blood plasma into the Bowman’s capsule – True

(d) Henle’s loop plays an important role in concentrating the urine – True

(e) Glucose is actively reabsorbed in the proximal convoluted tubule – True

4. Give a brief account of the counter current mechanism.

The chief adaptation for the conservation of water is the counter current mechanism that is functional inside the kidney. In the kidney there are two counter current mechanisms, namely:

1. Henle’s loop
2. Vasa rectae

• Henle’s loop is a U-shaped part of the nephron. The flow of blood in the two branches of the tube is in the opposite direction which gives rise to the counter currents.
• Vasa recta, on the other hand is an efferent arteriole that forms a capillary network around the tubules in the renal medulla which tracks parallel to the Henle’s loop. Vasa recta is also U-shaped. The flow of blood is in opposite directions in the two limbs of vasa recta. Hence, the blood that enters the renal medulla in the descending limb comes in close proximity with the outgoing blood in the ascending limb

• Through the counter current mechanism, the osmolarity increases in the cortex from 300 mOsmolL^-1 to about 1200 mOsmolL^-1 in the inner medulla which helps in sustaining the concentration gradient. This in turn aids in the easy movement of water from the collecting tubules. The concentration gradient is due to the movement of urea and Na Cl.

5. Describe the role of liver, lungs and skin in excretion.

The role of liver, lungs and skin in the process of excretion is as follows:

Liver:

• It is the chief site for the removal of inactivated products of steroid hormones, cholesterol, drugs and vitamins.
• Dead erythrocytes possess hemoglobin. This hemoglobin is also disintegrated into bile pigments – biliverdin and bilirubin which are treated wastes.
• Bile carries substances to the intestine which along with the wastes are eliminated

Lungs:

• Carbon dioxide is expelled out of the body by the lungs
• Approximately, it eliminates 200ml of carbon dioxide every minute
• Water in the form of water vapor is also eliminated
• Loss of water increases in colder conditions and declines in humid, hot conditions
• During the process of expiration, several volatile material are also ejected

Skin:

• It is chiefly responsible for thermoregulation(cooling) of the body
• Sweat is excreted by the skin. It contains nitrogenous wastes. Sweat is excreted only when necessary, such as to cool the body
• Sweat is excreted by the sweat glands, constitutes of urea, Na Cl and lactic acid
• Through the sebum, the sebaceous glands removes hydrocarbons, sterols and waxes
• A protective oily covering is provided to the skin by the sebum

6. Explain micturition.

Micturition is the process of releasing urine. Micturition is caused by a neural mechanism known as micturition reflex. The urinary bladder temporarily stores the urine that is formed. The bladder tends to stretch when the urinary bladder gets filled with urine. This stretching causes to initiate a signal, responding to this signal, the receptors located in the walls of the bladder sends out signals to the central nervous system (CNS). The CNS conveys motor messages that originate the relaxation of the urethral sphincters and the contraction of the smooth muscles of the urinary bladder, thereby resulting in micturition (passing of urine).

7. Match the items of column I with those of column II:

8. What is meant by the term osmoregulation?

Osmoregulation is the process of regulating the osmotic concentration in the cells of the body by checking the quantity of water and salts.

9. Terrestrial animals are generally either ureotelic or uricotelic, not ammoniotelic, why?

Ammonia is an extremely toxic nitrogenous waste. In order to reduce the toxicity of ammonia in the body, very large amount of water is necessary. To dilute ammonia, the bodies of terrestrial animals do not possess adequate quantity of water. If the body of terrestrial animals stores this excess ammonia, it may turn extremely poisonous for them. Hence in such animals, ammonia is always converted to less toxic uric acid and urea. This is the reason why terrestrial animals are generally either uricotelic or ureotelic.

10. What is the significance of juxta glomerular apparatus (JGA) in kidney function?

The juxtaglomerular apparatus is a specialized sensitive region that is formed by the cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact.

Significance:

• Its mechanism is via the renin-angiotensin-aldosterone system (RAAS)
• When the glomerular filtration rate dips, the juxtaglomerular apparatus stimulates causing the secretion of renin
• This renin converts a protein into a peptide, i.e., angiotensinogen to angiotensin
• Angiotensin is a hormone that elevates the GFR and the flow of blood in these three ways:
  1. Narrowing the efferent arterioles to cause an increase in the glomerular pressure
  2. Triggering the walls of the PCT in order to reabsorb more of water and NaCl
  3. Triggers the adrenal gland to secrete aldosterone that facilitates reabsorption of water and Na Cl in the DCT.
• The volume of blood and blood pressure thereby increases. The hypertonic urine and urine volume decreases.

11. Name the following:

(a) A chordate animal having flame cells as excretory structures

(b) Cortical portions projecting between the medullary pyramids in the human kidney

(c) A loop of capillary running parallel to the Henle’s loop.

(a)A chordate animal having flame cells as excretory structures – Amphioxus

Flame cells or protonephridia are the excretory structures found in some animals.

(b)Cortical portions projecting between the medullary pyramids in the human kidney – Columns of Bettini

The medulla is divided into several conical masses (medulla pyramids) that project into the calyces. The cortex extends in between the medullary pyramids as renal columns known as Columns of Bettini.

(c) A loop of capillary running parallel to the Henle’s loop – Vasa recta

A minute vessel of the network that runs parallel to the Henle’s loop forming a ‘U’ shaped vasa recta. Vasa recta is highly reduced in the cortical nephrons.

12. Fill in the gaps:

(a) Ascending limb of Henle’s loop is ______ to water whereas the descending limb is _______ to it.

(b) Reabsorption of water from distal parts of the tubules is facilitated by hormone _______.

(c) Dialysis fluid contain all the constituents as in plasma except _______.

(d) A healthy adult human excretes (on an average) _______ gm of urea/day

1. Impermeable, permeable
2. Vasopressin (anti-diuretic hormone)
3. Nitrogenous waste
4. 25-30

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