NCERT Solutions for Class 11 Biology Chapter 19

NCERT Solutions for Class 11 Biology Chapter 19 is a great resource for students to refer to while preparing for their Biology examinations. The solutions cover all the questions covered in Chapter 19 of the Class 11 Biology NCERT textbook and provide step-by-step and accurate answers. Students can use these resources in conjunction with the textbook to better prepare for their examinations in a better way. They can get a sense of how they should frame their answers to improve their performance. Also, these are a great resource for last-minute preparations.

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

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

NCERT Solutions for Biology Chapter 19 Class 11th

Making a career in Medical Sciences is tough as there is very high competition among students. NCERT Solutions Class 11 Biology Chapter 19 is a resource that can make things a little easier by providing students with detailed and accurate answers to the textbook questions. Special attention has been paid by our experts to give detailed and accurate answers that are as per the guidelines of CBSE.

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

Chapter 19 of Class 11 NCERT Biology textbook is called Excretory Products and their Elimination. It comes under Unit 5 of the textbook – Human Physiology. This chapter discusses the functioning of kidneys, urine formation process, filtrate concentration, information about many organs that are a part of the excretion process, and the disorders related to the said processes. Information about the excretion process in different animals, locational, and structural information of organs is included in this segment as well. Disorders like uremia, kidney failures, kidney stones, etc. are some of the other topics covered in this chapter. 

NCERT Solutions for Class 11 Biology Chapter 19 – Marks distribution

Excretory Products and Their Elimination NCERT Biology Chapter 19 is one of the chapters out of 7 present in Unit 5. Unit 5 carries a total weightage of 18 marks in the examinations. This is basically about 25% of the entire syllabus. The unit is important even for the NEET entrance exam as it makes up 20% of the total syllabus of the exam. 

Following Topics are Covered Under Class 11 Biology Chapter 19:

  • The Human Excretory System
  • Formation of Urine
  • The functioning of the tubules
  • Means of concentration of Filtrate
  • Kidney Function regulation
  • Micturition
  • Other organs participating in the process of Excretion
  • Disorders related to the process of Excretion and the Excretory system

Benefits of CBSE Class 11 Biology Chapter 19 NCERT Solutions

Key benefits of NCERT Class 11 Biology Chapter 19 Solutions are as follows:

  • The NCERT Solutions have been prepared in accordance with the CBSE mandated NCERT textbook. It is one of the most reliable and accurate guides that students can refer to. 
  • The solutions are detailed, step-by-step, and written in simple language.
  • Teachers and academic professionals with years of experience have been involved in the creation of these solutions.
  • These are a great resource for last-minute revisions and preparations before final exams.
  • Students will get a sense of how they should frame their answers in their final examinations.

Q.1 Define Glomerular Filtration Rate (GFR).

Ans-

Glomerular Filtration Rate (GFR) is the amount of filtrate formed by the kidneys per minute. It is measured in ml/min. In a healthy person, GFR is approximately 125 ml/min that is equal to 180 litres per day.

Q.2 Explain the autoregulatory mechanism of GFR.

Ans-

Kidneys maintain a uniform Glomerular Filtration Rate (GFR) with the help of the autoregulatory mechanism. Kidneys have a microscopic structure called juxta glomerular apparatus (JGA) located between an afferent arteriole and distal convoluted tube of the same nephron that is required for this auto-regulation. Whenever there is a fall in glomerular blood flow/glomerular blood pressure/GFR, cells of juxta glomerular apparatus release a hormone called renin which converts angiotensinogen in the blood to angiotensin I and further to angiotensin II.

  • Angiotensin II is a strong vasoconstrictor. It increases the glomerular blood pressure and blood flow and thereby, increases the GFR.
  • Angiotensin II also activates the release of Aldosterone which causes reabsorption of Na+ and water from the distal parts of the tubule. This also causes an increase in blood pressure and GFR.

Q.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.

Ans-

(a) True

(b) False

(c) True

(d) True

(e) True

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

Ans-

The transport of substances facilitated by a special arrangement of Henle’s loop of nephron and vasa recta is called counter current mechanism.

When fluid flows in these two tubes which are anti-parallel to each other, it forms a counter current. This helps mammals to produce concentrated urine. There are two counter current systems in human kidneys-

  • Henle’s loop consists of ascending and descending limbs. Fluid flows in the two limbs in opposite directions making a counter current system.
  • Second counter current system is made by vasa recta. Blood flows in the two limbs of vasa recta in anti-parallel direction.

Henle’s loop and vasa recta are positioned next to each other. Descending limb of Henle’s loop is anti-parallel to ascending limb of vasa recta and ascending limb of Henle’s loop is anti-parallel to descending limb of vasa recta. Counter current system and proximity of the loops help to increase the osmolarity (solute concentration) in inner medullary interstitium i.e. from 300mOsmolL-1 in the cortex to about 1200mOsmolL-1 in the inner medulla. Increased solute concentration in medullary interstitium causes water to come out of collecting duct making the urine concentrated. This system has the ability to concentrate urine upto four times depending upon the need.

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

Ans-

In addition to kidneys, liver, lungs and skin also play an important role in excretion of waste materials from the body.

Liver: It is the largest gland of the human body. Liver converts toxic ammonia into less toxic urea; thus carry out the detoxification role. It helps in the excretion of bile containing substances like bilirubin, biliverdin which are produced by the decomposition of haemoglobin pigment. Then bilirubin, biliverdin, urea along with other waste like cholesterol, degraded steroid hormones, vitamins and drugs are excreted by the liver. Finally, these substances are thrown out of the body along with digestive wastes.

Role of Lungs: Lungs diffuse out a large amount of gaseous waste like CO2 (18 litres/day) as part of normal respiration along with the significant quantity of water.

Role of Skin: Skin contains sweat and sebaceous glands which help in the excretion of many substances. The sweat produced by sweat glands secrete NaCl, small amounts of urea, lactic acid, etc., along with water. Sebaceous glands help in excretion by elimination of certain sterols, hydrocarbons and waxes through sebum.

Q.6 Explain micturition.

Ans-

Micturition is the process of releasing of urine from urinary bladder. Urine formed by kidney is carried to urinary bladder where it is stored. When urinary bladder is filled with urine, it exerts the pressure on bladder wall. Pressure activates receptors present in bladder wall that send signals to central nervous system (CNS). The CNS sends the signal for the contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincter causing the release of urine.

An adult human excretes about 1 to 1.5 litres of urine per day. The urine is light yellow coloured watery fluid which is slightly acidic with a characteristic odour.

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

Q.8 What is meant by the term osmoregulation?

Ans-

Osmoregulation is a process by which organisms maintain homeostasis of water content in their body. It protects body fluids from becoming too dilute or too concentrated. For example, large amount of water goes into the nephrons from blood during the process of glomerular filtration. This water is reabsorbed by medullary interstitium and transferred again to blood in vasa recta thus, maintaining water homeostasis in blood.

Q.9 Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic. Why?

Ans-

Terrestrial animals are generally either ureotelic or uricotelic because it is an adaptation to conserve water. In these animals, water soluble ammonia is converted into less soluble urea and uric acid. These are then filtered by the kidney and excreted out with urine. This requires minimum water; thus the animal conserves water.

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

Ans-

Kidneys have a microscopic structure called juxta glomerular apparatus (JGA) between an afferent arteriole and distal convoluted tubule of the same nephron that is required for the maintenance of uniform Glomerular Filtration Rate (GFR). Whenever there is a fall in GFR, cells of juxta glomerular apparatus release a hormone called renin which travels into the bloodstream of glomerulus where it converts angiotensinogen into angiotensin I. Angiotensin I further gets converted to angiotensin II. Angiotensin helps in constriction of smooth muscle cells of the blood vessel that increases the blood pressure. Increased blood pressure results in an increase in glomerular filtration rate. Angiotensin also stimulates the secretion of aldosterone from adrenal glands. Aldosterone increases the absorption of sodium ions and water which increases blood pressure and brings the GFR back to normal. Thus, juxta glomerular apparatus plays a complex regulatory role in the functioning of the kidney.

Q.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 Henle’s loop

Ans-

(a) Amphioxus
(b) Columns of Bertini
(c) Vasa recta

Q.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 contains all the constituents as in plasma except _______.
(d) A healthy adult human excretes (on an average) _______ gm of urea/day.

Ans-

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

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

(c) Dialysis fluid contains all the constituents as in plasma except the nitrogenous waste.

(d) A healthy adult human excretes (on an average) 25-30 gm of urea/day.

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FAQs (Frequently Asked Questions)

The amount of glomerular filtrate that is formed per minute in all the nephrons present in both the kidneys is called glomerular filtration rate (GFR). Glomerular filtrate consists of amino acids, glucose, ketone bodies, potassium, urea, sodium, uric acid, and water. 125 ml/minute is the GFR in a healthy person.

The glomerular filtration rate is regulated by the kidneys by an autoregulatory mechanism. Juxtaglomerular apparatus is the microscopic structure found between the renal corpuscle’s vascular pole and the returning DCT of the same nephron. This is what regulates the renal blood flow and the GFR.

The role of the lungs is specified well in the Class 11 Biology Chapter 19 NCERT textbook. Carbon dioxide is expelled from the body with the help of the lungs. About 200 ml per minute of carbon dioxide is eliminated from the body. Not only CO2 but water as well is released in the form of vapour. In humid conditions, this loss of water is reduced while in cold conditions it is increased. Several volatile minerals also get eliminated in this process of elimination.

GFR or Glomerular Filtration Rate is a test that aids in determining how the kidneys are functioning. The level of creatinine in the blood can be measured using this. Results are utilised in a formula and calculation is carried out to find a number that indicates how the kidney is functioning. This number is called eGFR or estimated GFR. 

The process of discharge of urine from the urinary bladder is called Micturition. The solid dividers of the bladder extend as the urine keeps getting collected. Once the bladder is filled with urine, nerves present in it are triggered and individuals feel an urge to urinate. Leakage of urine is prevented by the circular sphincter muscles. Signals to contract are sent by the brain to the urinary bladder. The urinary bladder’s receptors send signals to the central nervous system which leads to the contraction of the urinary bladder. The circular sphincter muscles loosen and allow the passage of urine through the urethra. This expulsion of urine is called micturition. About 1-1.5 litres of urine is discharged by a grown human every day.

Micturition has two phases, namely the storage phase and the voiding phase. The storage phase is when all the urine gets collected in the urinary bladder. Circular sphincter muscles around the urethra prevent urine leakage. The voiding phase includes the triggering of nerves which incites an urge to urinate once the bladder is full. The urinary bladder has receptors that send signals to the nervous system. The system then sends a signal that causes the contraction of the bladder. Then the passage of urine through the urethra occurs. 

The process of micturition is influenced by several factors. While physical trauma or disease are some of these factors, some are of psychological nature as well. Here are a few disorders that impact micturition;

  • Urinary retention – Urinary retention is when one cannot empty their bladder fully. This condition may occur suddenly or gradually and its causes can range from weak bladder muscles or a nerve problem to urethra blockage.
  • Spinal Cord Trauma – The bladder can be overactive or there can be urinary incontinence due to injuries to the spinal cord (especially the tenth thoracic vertebra or T10).
  • Detrusor Instability – Detrusor instability occurs when contraction of the detrusor muscle takes place without any reason. Detrusor instability leads to urinary incontinence as it is a muscle responsible for bladder contraction. Hence, this condition tampers with the micturition process.  

GFR has an autoregulatory system that is regulated with the help of a juxtaglomerular apparatus. The juxtaglomerular apparatus regulates the renal blood flow and the GFR. When there is a fall in GFR, juxtaglomerular cells get activated and release renin. Glomerular blood flow is stimulated by the renin that is released. This in turn results in the activation of the renin-angiotensin mechanism. This leads to GFR being raised and normalised.