Chapter 16 - Excretory Products and their Elimination
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NCERT Solutions Class 11 Biology Chapter 16 explains that glomerular filtration takes place in the renal corpuscle, where blood is filtered through the glomerulus into Bowman’s capsule.
NCERT Solutions Class 11 Biology Chapter 16 explains that the proximal convoluted tubule reabsorbs most of the water, electrolytes, and useful substances such as glucose and amino acids from the glomerular filtrate.
NCERT Solutions Class 11 Biology Chapter 16 explains that the loop of Henle and vasa recta help maintain an osmotic gradient in the kidney medulla. This gradient allows water to be reabsorbed from the collecting ducts, producing concentrated urine.
NCERT Solutions Class 11 Biology Chapter 16 identifies antidiuretic hormone (ADH) as the hormone that increases water reabsorption, particularly in the distal parts of the nephron and collecting ducts.
NCERT Solutions Class 11 Biology Chapter 16 explains that renin helps initiate the formation of angiotensin II, which raises blood pressure and helps maintain glomerular filtration. Angiotensin II also stimulates aldosterone release, increasing sodium reabsorption in the kidneys.
NCERT Solutions Class 11 Biology Chapter 16 explains that ammonotelic animals excrete ammonia, ureotelic animals mainly excrete urea, and uricotelic animals mainly excrete uric acid.
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NCERT Solutions Class 11 Biology Chapter 16 - Excretory Products and their Elimination
NCERT Solutions for Class 11 Biology Chapter 16 (Excretory Products and Their Elimination) explain how the human body removes harmful waste products and maintains the balance of water and salts. The chapter covers the human urinary system, the structure and functions of the kidneys, and the role of nephrons in removing wastes from the blood. Students can learn how the body forms urine and maintains its internal balance.
NCERT Solutions for Class 11 Biology Chapter 16 by ALLEN describe urine generation, counter-current mechanism and hormonal modulation of kidney function. Students can learn about the different parts of the nephron, including the PCT, Loop of Henle, and DCT, and understand their functions. The chapter also covers micturition, haemodialysis, and kidney disorders such as uremia, renal calculi, and glomerulonephritis. These solutions help students revise NCERT topics and prepare for school exams and NEET.
1.0Class 11 Biology Chapter 16 Excretory Products and Their Elimination: Key Concepts
Class 11 Biology Chapter 16, Excretory Products and Their Elimination, explains how the human body removes metabolic wastes and maintains the balance of water and salts. The chapter covers the human excretory system, the structure of nephrons, urine formation, the regulation of kidney function, and common excretory disorders.
Modes of Excretion: Learn about ammonotelic animals that excrete ammonia, ureotelic animals that excrete urea, and uricotelic animals that excrete uric acid.
Human Excretory System: Understand the structure of the kidneys, including the renal hilum, cortex, and medulla.
Structure of the Nephron: Study the nephron, the functional unit of the kidney, including the glomerulus, Bowman's capsule, proximal convoluted tubule (PCT), Loop of Henle, distal convoluted tubule (DCT), and collecting duct.
Urine Formation: Learn about the three main steps of urine formation: glomerular filtration, selective reabsorption, and tubular secretion.
Functions of Kidney Tubules: Understand how different parts of the nephron reabsorb useful substances, remove wastes, and help maintain water, salt, and pH balance.
Counter-Current Mechanism: Learn how the Loop of Henle and vasa recta help create the concentration gradient needed to produce concentrated urine.
Regulation of Kidney Function: Understand the roles of antidiuretic hormone (ADH), the juxtaglomerular apparatus (JGA), and atrial natriuretic factor (ANF) in regulating kidney function and fluid balance.
Micturition: Learn how urine is stored in the urinary bladder and removed from the body through the micturition reflex.
Role of Other Organs in Excretion: Understand how the lungs, liver, and skin help remove waste products from the body.
Excretory Disorders: Study uremia, renal calculi (kidney stones), and glomerulonephritis, along with the use of haemodialysis when kidney function is severely affected.
2.0Detailed NCERT Textbook Solutions : Class 11 Biology Chapter 16
Define Glomerular Filtration Rate (GFR).
Ans. The amount of filtrate formed by the kidneys per minute is called glomerular filtration rate (GFR). In a healthy person it is approximately 125 mL/min. i.e., 180 liters per day.
Explain the auto regulatory mechanism of GFR.
Ans. The kidneys have built-in mechanisms for the regulation of glomerular filtration rate. One such efficient mechanism is carried out by juxta glomerular apparatus (JGA). JGA is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact. A fall in GFR can activate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR back to normal.
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
Give a brief account of the counter current mechanism.
Ans. Mammals have the ability to produce a concentrated urine. The Henle's loop and vasa recta play a significant role in this. The flow of filtrate in the two limbs of Henle's loop is in opposite directions and thus forms a counter current. The flow of blood through the two limbs of vasa recta is also in a counter current pattern. The proximity between the Henle's loop and vasa recta, as well as the counter current in them help in maintaining an increasing osmolarity towards the inner medullary interstitium, i.e., from 300mOsmolL−1 in the cortex to about 1200mOsmolL−1 in the inner medulla. This gradient is mainly caused by NaCl and urea. NaCl is transported by the ascending limb of Henle's loop which is exchanged with the descending limb of vasa recta. NaCl is returned to the interstitium by the ascending portion of vasa recta. Similarly, small amounts of urea enter the thin segment of the ascending limb of Henle's loop which is transported back to the interstitium by the collecting tubule. The above described transport of substances facilitated by the special arrangement of Henle's loop and vasa recta is called the counter current mechanism. This mechanism helps to maintain a concentration gradient in the medullary interstitium. Presence of such interstitial gradient helps in an easy passage of water from the collecting tubule thereby concentrating the filtrate (urine). Human kidneys can produce urine nearly four times concentrated than the initial filtrate formed.
Describe the role of liver, lungs and skin in excretion.
Ans. Other than the kidneys, lungs, liver and skin also help in the elimination of excretory wastes. Lungs remove large amounts of CO2 (approximately, 200ml/min ) and also significant quantities of water every day. Liver secretes bile which contains substances like bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins and drugs. Most of these substances ultimately pass out along with digestive wastes. The sweat and sebaceous glands in the skin can eliminate certain substances through their secretions. Sweat produced by the sweat glands is a watery fluid containing NaCl, small amounts of urea, lactic acid etc. Sebaceous glands eliminate certain substances like sterols, hydrocarbons and waxes through sebum.
Explain micturition.
Ans. Urine formed by the nephrons is ultimately carried to the urinary bladder where it is stored till a voluntary signal is given by the central nervous system (CNS). This signal is initiated by the stretching of the urinary bladder as it gets filled with urine. In response, the stretch receptors on the walls of the bladder send signals to the CNS. The CNS passes on motor messages to initiate the contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincter causing the release of urine. The process of release of urine is called micturition and the neural mechanisms causing it is called the micturition reflex. An adult human excretes, on an average, 1 to 1.5 litres of urine per day. The urine formed is a light yellow coloured watery fluid which is slightly acidic (pH-6.0) and has a characterestic odour. On an average, 25-30 gm of urea is excreted out per day. Various conditions can affect the characteristics of urine. Analysis of urine helps in clinical diagnosis of many metabolic discorders as well as malfunctioning of the kidney. For example, presence of glucose (Glycosuria) and ketone bodies (Ketonuria) in urine are indicative of diabetes mellitus.
Match the items of column I with those of column II.
Column-I
Column-II
Ammonotelism
Birds
Bowman's capsule
Water-reabsorption
Micturition
Bony fish
Uricotelism
Urinary bladder
ADH
Renal tubule
Ans. (a) - (iii), (b) - (v), (c) - (iv), (d) - (i), (e) - (ii)
What is meant by the term osmoregulation?
Ans. The regulation of water and ionic balance of body fluids is called osmoregulation.
Terrestrial animals are generally either ureotelic or uriotelic, not ammonotelic, why?
Ans. Ammonia is highly toxic and requires a large amount of water for its elimination. Terrestrial animals live in habitats where water availability is limited. Therefore, they generally excrete the less toxic nitrogenous wastes, urea or uric acid, which helps in conservation of water.
What is the significance of juxta glomerular apparatus (JGA) in kidney function?
Ans. Juxta glomerular apparatus (JGA) is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact. The JGA plays a complex regulatory role. A fall in glomerular blood flow/ glomerular blood pressure/GFR can activate the JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II. Angiotensin II, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. Angiotensin II also activates the adrenal cortex to release aldosterone. Aldosterone causes reabsorption of Na+ and water from the distal parts of the tubule. This also leads to an increase in blood pressure and GFR.
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.
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 ADH.
(c) Dialysis fluid contains all the constituents as in plasma except nitrogenous wastes.
(d) A healthy adult human excretes (on an average) 25-30 gm of urea/day.
3.0NCERT Class 11 Biology – Chapter-Wise Solutions & Explanations
Get chapter-wise NCERT Solutions for Class 11 Biology with answers to all textbook questions. Learn important topics, revise the syllabus, and prepare well for your Biology exams.
4.0Key Features of NCERT Solutions for Class 11 Biology Chapter 16
Functions of Different Nephron Parts: Understand what substances are reabsorbed and secreted in each part of the nephron, including the PCT, Loop of Henle, DCT, and collecting duct.
Counter-Current Mechanism: Learn how the Loop of Henle and vasa recta help maintain a concentration gradient in the kidney and produce concentrated urine.
Regulation of Kidney Function: Understand how the juxtaglomerular apparatus (JGA) and hormones help regulate kidney function and blood pressure.
Glomerular Filtration: Learn how pressure differences help filter blood in the glomerulus and how the filtration membrane allows water and small substances to pass into Bowman's capsule.
Prepared by ALLEN Expert Faculty: Study clear explanations of kidney structure, urine formation, and the regulation of water and salt balance based on the NCERT Class 11 Biology syllabus.
Haemodialysis: Understand how an artificial kidney removes waste products from the blood using a semipermeable membrane.
Complete NCERT Exercise Solutions: Find clear answers to NCERT textbook questions to revise Excretory Products and Their Elimination and prepare for school exams and NEET.