Excretory Products and their Elimination - Class 11 Biology - Chapter 15 - Notes, NCERT Solutions & Extra Questions
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Extra Questions - Excretory Products and their Elimination | NCERT | Biology | Class 11
Match the excretory organ to the correct organism.
Option A) Earthworm
Option B) Flatworm
Option C) Paramecium
Option D) Cockroach
To match each excretory organ to the correct organism:
Earthworm (Option A):
Utilizes nephridia, which function as primitive kidneys.
Flatworm (Option B):
Employs protonephridia as their primitive excretory structures.
Paramecium (Option C):
Uses contractile vacuoles to excrete wastes and excess water.
Cockroach (Option D):
Features Malpighian tubules that remove wastes from the body fluid, extending into the alimentary canal.a
Each organism has a distinct type of excretory system tailored to its physiological needs and complexity.
Which of the following is an incorrect pair of an organism and their respective excretory organs?
A Earthworm - Nephridia
B Insects - Malpighian tubules
C Fishes - Kidneys
D Frogs - Kidneys
The correct option is B (Insects - Nephridia). Among the given options, Frogs, Fishes, and other higher organisms use kidneys as their excretory organs. Earthworms, on the other hand, have Nephridia as their primary excretory system. For insects such as cockroaches, the correct excretory organs are Malpighian tubules, not Nephridia. Thus, the pairing of "Insects - Nephridia" is incorrect.
Metanephros kidney occurs in
A) Amniotes
B) Fishes
C) Amphibians
D) Invertebrates
The correct answer is Option A: Amniotes.
Metanephros kidneys are fully developed kidneys that appear in amniotes. Amniotes are a group of land-dwelling vertebrates that lay eggs on land or retain the fertilized egg within the mother. This group includes reptiles, birds, and mammals.
What are the different entry routes of allergens?
A. Through the nose
B. Through the mouth
C. Through the hairs
D. Through the skin
The correct entry routes for allergens are:
A: Through the nose
B: Through the mouth
D: Through the skin
Allergens, which are substances that trigger allergic reactions, can enter the body through various channels. Highlighted routes include:
Through the nose: When breathing, allergens such as pollen grains, dust, and animal hair can be inhaled, entering the body via the respiratory tract.
Through the mouth: Ingestion of food containing allergens, like milk, eggs, or fish, along with certain medicines, can introduce allergens to the body internally.
Through the skin: Allergies can also be triggered via the skin due to direct contact with insect bites or stings, metals, cosmetics, or even strong sunlight.
It's important to note routes like C: Through the hairs are incorrect since hair itself does not serve as a direct entry point for allergens into the body’s systems.
In earthworm,
A. Pharyngeal and septal nephridia are exonephric.
B. Integumentary and pharyngeal nephridia are exonephric.
C. Pharyngeal and septal nephridia are enteronephric.
D. Integumentary and septal nephridia are enteronephric.
Correct Answer: C. Pharyngeal and septal nephridia are enteronephric.
In earthworms, the pharyngeal and septal nephridia are classified as enteronephric. This indicates that these nephridia are involved in managing excretion from within the body cavity. On the other hand, integumentary nephridia are exonephric and function in excreting substances directly from the body surface to the external environment.
Choose the correct statement:
A. Lizards show autotomy.
B. Most lizards are oviparous.
C. Poison glands in snakes are modified parotid glands.
D. All of the above.
The correct statement is D. All of the above.
Autotomy is a defense mechanism employed by lizards wherein they voluntarily shed part of their tails to escape predators. This confirms that statement A is true.
Most lizards reproduce by laying eggs, making them oviparous. Therefore, statement B is correct.
In snakes, the poison glands are indeed modified parotid glands, which are specialized to secrete venom. This validates statement C as true.
Thus, all the given statements A, B, and C are correct, making D the correct answer.
Sweat is released through the ______ present on the skin.
A) pimples B) papillae C) hair D) pores
The correct answer is D) pores.
Pores are small openings on the skin's surface through which sweat is released. This liquid helps in cooling the body and eliminating waste products.
Why do shoes, purses, and leather items have silica gel pouches kept in them?
A. for absorption of moisture
B. for insect repellent
C. for adsorption of moisture
D. for all of the above
The correct answer is C for adsorption of moisture.
Silica gel acts as a powerful adsorbent, which means it has the ability to attract and hold moisture molecules from its surroundings. This property stems from its large surface area, especially when in a finely divided state. By including silica gel pouches in shoes, purses, and other leather items, the gel adsorbs moisture effectively, hence keeping these products dry and free from moisture damage.
Which of the following is least likely to be present in glomerular filtrate (the filtrate produced by the nephron before it enters the loop of Henle) of a healthy adult nephron?
A. Amino acid
B. Glucose
C. Electrolytes
D. Large molecular weight protein
The correct answer is D. Large molecular weight protein
In the filtration process of the kidneys, substances such as electrolytes, glucose, and amino acids are commonly filtered from the blood into the glomerular filtrate and later reabsorbed. However, large molecular weight proteins are typically too large to pass through the filtration barrier of the glomerulus. Therefore, they are least likely to be found in the glomerular filtrate of a healthy adult.
The condition in which excess glucose passes with urine is:
Glycosuria is defined as the presence of an excessive amount of glucose in the urine. This condition is commonly related to diabetes or kidney disease. Under normal circumstances, glucose that enters the nephron—via ultrafiltration in the kidneys—is reabsorbed by the body. However, in cases of glycosuria, the kidneys fail to reabsorb adequate glucose from the urine before it is excreted. Consequently, the glucose levels in the urine increase.
This can occur when blood glucose levels are exceptionally high, as often seen in diabetes. Alternatively, glycosuria might stem from kidney issues, in which case it is referred to as renal glycosuria.
If for some reason our goblet cells are non-functional, this will adversely affect:
A. Production of somatostatin
B. Secretion of sebum from the sebaceous glands
C. Maturation of sperm
D. Smooth movement of food downwards the intestine
The correct answer is D. Smooth movement of food downwards the intestine.
Goblet cells are located in the columnar epithelium of the mammalian intestine and are responsible for secreting mucin, a key component in mucus production. Mucin plays a vital role in lubricating the intestine, facilitating the smooth transit of food through the digestive tract. If goblet cells are non-functional, the production of mucin would be impaired, leading to difficulties in the smooth movement of food downwards the intestine. This absence of mucin would therefore adversely affect intestinal function.
In humans, the urinary bladder opens into:
A) Urethra
B) Uterus
C) Vestibule
D) Ureter
The correct answer is A) Urethra.
In humans, the urinary bladder is linked to the urethra, which is the tube through which urine exits the body. This connection facilitates the process of urination. The options B) Uterus, C) Vestibule, and D) Ureter do not correctly describe the opening of the urinary bladder in the human body.
Arrange the following in the correct sequence:
Urine enters the ureter.
Urine is stored in the urinary bladder.
Some substances in the initial filtrate are selectively reabsorbed.
(A) 1 → 2 → 3 (B) 2 → 3 → 1 (C) 3 → 1 → 2 (D) 3 → 2 → 1
The sequence begins with step 3, where "Some substances in the initial filtrate are selectively reabsorbed." This process occurs in the nephrons, which are part of each kidney. Here, essential substances are reabsorbed back into the bloodstream as the urine flows through the nephron.
Next is step 1. After the filtration and reabsorption processes, the urine that remains is directed from the kidneys to the "Urine enters the ureter." The ureter is a tube that connects each kidney to the urinary bladder, effectively transporting the urine.
Finally, step 2 concludes the sequence with "Urine is stored in the urinary bladder." Here, the urine accumulates until the bladder fills to a certain capacity, which then triggers the urge to void through the urethra.
The correct sequence is thus represented by option (C) 3 → 1 → 2. This order effectively describes the flow and processing of urine, starting from its filtration and selective reabsorption in the kidneys, through its passage via the ureters, and its storage in the bladder until excretion.
Blood collects the waste material from the tissues and takes it to the $\qquad$ where it is filtered.
A. Pancreas
B. Spleen
C. Liver
D. Kidneys
The correct answer is D. Kidneys.
Blood circulates through the body and picks up waste materials produced by cells. These wastes are transported to various organs for disposal. The kidneys play a crucial role in this process. They possess a complex system of blood capillaries which allows for the filtration of waste materials from the blood. Simultaneously, they help in reabsorbing useful substances and excess water back into the bloodstream. This dual function ensures that blood purification and fluid balance are maintained efficiently within the body.
Which of the following is/are not correct with respect to nephron and its parts?
A. It is the functional unit of the excretory system.
B. Proximal convoluted tubule lies close to the malpighian corpuscles.
C. A 'U' shaped vasa recta is formed from efferent arterioles.
D. None of the above
The correct option is D: None of the above.
The nephron is indeed the functional unit of the excretory system, consisting of two main parts: the renal (or Malpighian) corpuscle and the renal tubules.
The Proximal Convoluted Tubule (PCT) is aptly named because it is located proximally, meaning 'near', to the Malpighian corpuscle. This proximity justifies the naming and the functional relationship.
Efferent arterioles, branching from the renal artery, play a critical role by draining blood away from the glomerulus. These arterioles are crucial in connecting the glomerulus to the peritubular capillaries and the vasa recta. The vasa recta forms a ‘U’ shape around the loop of Henle, which aids in the concentration of urine.
Thus, all statements given in the options accurately describe nephron and its components, making option D the correct choice.
"What is nephridia?"
Nephridia are organs found in invertebrates that play a crucial role in the elimination of metabolic wastes. They act similarly to kidneys in vertebrates and are typically paired within the organism.
The main functions of the small intestine are:
A. Ingestion
B. Digestion
C. Absorption
D. Egestion
The correct answers are:
B. Digestion
C. Absorption
The small intestine primarily functions to complete the digestion of nutrients. Additionally, it is essential for the absorption of these digested nutrients into the bloodstream after digestion.
The glomerulus and Bowman's capsule together are known as the:
A) renal corpuscle B) PCT C) DCT D) renal tubule
The correct answer is A) renal corpuscle.
The glomerulus is essentially a network of capillaries, which originates from an afferent arteriole—a subdivision of the renal artery. Blood from the glomerulus is then drained by an efferent arteriole. Surrounding the glomerulus is the Bowman's capsule, a cup-shaped structure that encases it. Together, the glomerulus and Bowman’s capsule are referred to as the renal corpuscle or the malpighian body. The renal corpuscle acts as the primary blood-filtering unit of the nephron in the kidney.
Define Glomerular Filtration Rate (GFR).
Definition of Glomerular Filtration Rate (GFR)
Glomerular Filtration Rate (GFR) refers to the total volume of fluid filtered from the glomerular capillaries into the Bowman's capsule per unit time, across all nephrons in both kidneys. In a healthy adult, GFR is typically around 125 mL per minute. The composition of the glomerular filtrate includes substances like glucose, amino acids, sodium, potassium, urea, uric acid, ketone bodies, and a substantial quantity of water.
Which of the following is the most toxic waste matter and requires lots of water to be flushed out of the body?
A. Urea
B. Uric acid
C. Ammonia
D. Hippuric acid
The correct answer to the question is C. Ammonia.
Ammonia is characterized by having one nitrogen per molecule and is highly toxic. It necessitates a substantial amount of water to efficiently flush it out of the body. In comparison:
Urea, which has two nitrogens per molecule, is less toxic and demands less water for excretion.
Uric acid contains four nitrogens per molecule but is non-toxic, needing very little water to be excreted.
Hippuric acid was not discussed in detail but is generally less relevant in the context of this specific question about toxicity and water requirement for excretion.
Arrange the processes in the large intestine in the proper order: I. Absorption of water II. Absorption of ions and nutrients III. Defecation
A) I $\rightarrow$ II $\rightarrow$ III
B) III $\rightarrow$ II $\rightarrow$ I
C) II $\rightarrow$ I $\rightarrow$ III
D) III $\rightarrow$ I $\rightarrow$ II
The correct sequence in the large intestine is given by option C: II $\rightarrow$ I $\rightarrow$ III.
Functions of the Large Intestine
Absorption of ions and nutrients: Initially, the large intestine absorbs ions and essential nutrients from the semi-digested content that enters from the small intestine.
Absorption of water: Following nutrient absorption, around 80% of water is absorbed in the colon, which is vital for maintaining body fluid balance.
Defecation: After water absorption, the remaining waste solidifies and the process of defecation occurs, wherein solid waste is expelled through the anus.
Thus, the processes occur in the following order: Absorption of nutrients and ions, followed by water absorption, culminating in defecation.
The incorrect statement about DDT is:
A The problems related to extensive use of DDT began to appear in the early 1970s.
B Many species of insects developed resistance to DDT, and it was also discovered to have high toxicity towards fish.
C The chemical stability of DDT and its fat solubility further increased the problems.
D DDT is not completely biodegradable and gets deposited in fatty tissues; its use has been banned in the USA since 1973.
The incorrect statement about DDT is:
Option B: Many species of insects developed resistance to DDT, and it was also discovered to have high toxicity towards fish.
Explanation: DDT has been extensively used as insecticide particularly against mosquitoes, which are vectors for malaria. However, despite the issues of resistance and toxicity highlighted in Option B, these are actually correct and well-documented consequences of DDT usage. The assertion that many insect species developed resistance to DDT and its high toxicity towards fish represents factual outcomes resulting from the widespread use of DDT. Therefore, this statement is indeed correct, making the labeling of it as 'incorrect' a mistake.
Which among the following chemicals kill the microbes that clean the water?
A Paints
B Medicines
C Insecticides
D All of these
The correct answer is D. All of these.
Paints, medicines, and insecticides are all chemicals that, if improperly disposed of in water systems such as sinks or toilets, can have a detrimental effect on the microbial populations that help clean and purify water by breaking down organic materials. Thus, all of these chemicals can kill the microbes essential for water treatment processes.
Which part of the excretory system stores urine?
Option 1: Ureters
Option 2: Kidney
Option 3: Urethra
Option 4: Urinary bladder
The correct option is Option 4: Urinary bladder
The main components of the excretory system are the kidneys, ureters, urinary bladder, and the urethra. Urine, which is produced by the kidneys, flows through the ureters to the urinary bladder. It is in the urinary bladder where urine is stored before it is eventually expelled from the body through the urethra.
Statement 1: Bile pigment is formed in the liver by the breakdown of haemoglobin in dead RBCs.
Statement 2: Vitamins are not excreted along with urine.
Phenylalanine
Tyrosine
Valine replacing glutamine
Homogentisic acid
The correct option is A) Phenylalanine
Explanation:
Bile pigments are formed in the liver through the breakdown of haemoglobin in dead RBCs. The liver is renowned for its ability to metabolize numerous compounds and toxins, thereby facilitating their elimination from the body.
Many of these compounds, after initial processing in the liver, are reabsorbed in the small intestine and are ultimately eliminated by the kidneys.
Our body requires salts and other substances only in specific amounts. Any excess salt and water-soluble vitamins are excreted along with urine.
Therefore, Statement 1 is true: Bile pigments form in the liver by breaking down haemoglobin in dead RBCs.
However, Statement 2 is false: While some vitamins, particularly water-soluble ones, are indeed excreted in urine when in excess.
Consider the following statements:
Statement 1: Bile is produced by the Liver.
Statement 2: Pancreatic juice is also secreted by the Liver.
Both are correct
Both are incorrect
Only 1 is correct
Only 2 is correct
The correct option is C: Only 1 is correct.
Bile is produced by the Liver, but pancreatic juice is produced by the Pancreas. Therefore, the second statement is incorrect.
Match the following regarding the excretory system and choose the correct one.
Column - I | Column - II |
---|---|
A) Proximal convoluted tubule | 1) Formation of concentrated urine |
B) Distal convoluted tubule | 2) Filtration of blood |
C) Henle's loop | 3) Reabsorption of 70-80% of electrolytes |
D) Counter current | 4) Ionic balance mechanism |
E) Renal corpuscle | 5) Maintenance of concentration of gradient in renal medulla |
1) A - 3, B - 5, C - 4, D - 2, E - 1
2) A - 3, B - 4, C - 1, D - 5, E - 2
3) A - 1, B - 3, C - 2, D - 5, E - 4
4) A - 3, B - 1, C - 4, D - 5, E - 2
Given the task to match parts of the nephron with their respective functions and identifying the correct sequence, we can analyze the options using the provided explanations.
Column Matching:
Proximal Convoluted Tubule (PCT):
Function: Reabsorption of 70-80% of electrolytes.
Matching Pair: A - 3
Distal Convoluted Tubule (DCT):
Function: Ionic balance mechanism.
Matching Pair: B - 4
Henle's Loop:
Function: Formation of concentrated urine.
Matching Pair: C - 1
Countercurrent Mechanism:
Function: Maintenance of concentration gradient in renal medulla.
Matching Pair: D - 5
Renal Corpuscle:
Function: Filtration of blood.
Matching Pair: E - 2
Correct Sequence:
Option 2: A - 3, B - 4, C - 1, D - 5, E - 2
Verification:
Proximal Convoluted Tubule with Reabsorption of 70-80% of electrolytes: A - 3
Distal Convoluted Tubule with Ionic balance mechanism: B - 4
Henle's Loop with Formation of concentrated urine: C - 1
Countercurrent Mechanism with Maintenance of concentration gradient in renal medulla: D - 5
Renal Corpuscle with Filtration of blood: E - 2
Thus, the correct match is indeed option 2.
Final Answer:
B)
Match the following regarding the excretory system and choose the correct one:
Column - I | Column - II |
---|---|
A) JG Cells | 1) Vasodilator |
B) Hypothalamus | 2) Vasoconstrictor |
C) Angiotensin II | 3) Vasopressin |
D) ANF | Renin |
1) A - 4, B - 3, C - 2, D - 1
2) A - 3, B - 2, C - 1, D - 4
3) A - 2, B - 1, C - 3, D - 4
4) A - 2, B - 1, C - 4, D - 3
Match the following regarding the excretory system and choose the correct one:
Given pairs to match:
Column I:
A) JG cells
B) Hypothalamus
C) Angiotensin II
D) ANF
Column II:
Vasodilator
Vasoconstrictor
Vasopressin
Renin
Correct Match:
A - 4
: JG cells (Juxtaglomerular cells) secrete renin, which is involved in regulating blood pressure.B - 3
: The hypothalamus regulates the pituitary gland, which releases vasopressin (also known as antidiuretic hormone, ADH).C - 2
: Angiotensin II acts as a vasoconstrictor; it helps increase blood pressure by narrowing blood vessels.D - 1
: ANF (Atrial Natriuretic Factor) functions as a vasodilator, which helps reduce blood pressure by widening blood vessels.
Here is the correctly matched pair:
A - 4
B - 3
C - 2
D - 1
Therefore, the correct option is:
Option 1: A-4, B-3, C-2, D-1
Match the following regarding the excretory system and choose the correct one.
Column - I | Column - II |
---|---|
A) Proximal convoluted tubule | 1) Simple epithelium |
B) Collecting duct | 2) Simple cuboidal epithelium |
C) Bowman's Capsule | 3) Simple squamous epithelium |
D) Urinary bladder | 4) Transitional epithelium |
1) A - 4, B - 3, C - 2, D - 1
2) A - 3, B - 2, C - 1, D - 4
3) A - 2, B - 1, C - 3, D - 4
4) A - 2, B - 1, C - 4, D - 3
To match the pairs regarding the excretory system and select the correct answer from the given options, we can analyze each term in Column-I and find its corresponding match in Column-II.
Column-I and Column-II Analysis:
A) Proximal convoluted tubule
Description: The proximal convoluted tubule (PCT) has an epithelium with cube-shaped cells forming a single layer.
Match: Simple cuboidal epithelium (2).
B) Collecting duct
Description: The collecting duct is lined with a simple type of epithelium.
Match: Simple epithelium (1).
C) Bowman's capsule
Description: Bowman's capsule has flat, scale-shaped cells known as parietal cells, forming a single layer.
Match: Simple squamous epithelium (3).
D) Urinary bladder
Description: The urinary bladder’s cell layer changes shape, becoming flattened when stretched.
Match: Transitional epithelium (4).
Correct Matches:
A) Proximal convoluted tubule: 2 (Simple cuboidal epithelium)
B) Collecting duct: 1 (Simple epithelium)
C) Bowman's capsule: 3 (Simple squamous epithelium)
D) Urinary bladder: 4 (Transitional epithelium)
Final Answer:
The correct pairing as per the given options is:
Option 3:
$ A \rightarrow 2 $
$ B \rightarrow 1 $
$ C \rightarrow 3 $
$ D \rightarrow 4 $
Hence, the correct answer is option 3.
Match the following regarding the excretory system and choose the correct one.
Column - I | Column - II |
---|---|
A) Urochrome | 1) Urea forms in liver |
B) Ornithine cycle | 2) Colour of urine |
C) Angiotensinogen | 3) Concave border of kidney |
D) Hilum | 4) Produced by liver |
1) A - 4, B - 3, C - 2, D - 1
2) A - 3, B - 2, C - 3, D - 4
3) A - 2, B - 1, C - 3, D - 4
4) A - 2, B - 1, C - 4, D - 3
To solve the matching problem regarding the excretory system, we need to pair each item in Column I with its corresponding explanation in Column II.
Here is the solution in a structured manner:
Column-I and Column-II Matching:
A) Urochrome
Urochrome is the pigment responsible for the color of urine.
Match: A → 2
B) Ornithine cycle
The Ornithine cycle is the biological pathway that converts toxic ammonia into less toxic urea, which takes place in the liver hepatocytes.
Match: B → 1
C) Angiotensinogen
Angiotensinogen is a peptide hormone produced by the liver. It regulates vasoconstriction, blood pressure, and hypertension.
Match: C → 4
D) Hilum
The Hilum is the concave border of the kidney where structures such as blood vessels and nerves enter and leave the kidney.
Match: D → 3
Correct Matching Pair:
A → 2 (Urochrome: Colour of urine)
B → 1 (Ornithine cycle: Urea forms in the liver)
C → 4 (Angiotensinogen: Produced by the liver)
D → 3 (Hilum: Concave border of kidney)
Option Analysis:
Option 1: A - 4, B - 3, C - 2, D - 1
Option 2: A - 3, B - 2, C - 1, D - 4
Option 3: A - 2, B - 1, C - 3, D - 4
Option 4: A - 2, B - 1, C - 4, D - 3
Final Answer:
The correct option is Option 4: A - 2, B - 1, C - 4, D - 3
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Ask Chatterbot AINCERT Solutions - Excretory Products and their Elimination | NCERT | Biology | Class 11
Define Glomerular Filtration Rate (GFR)
Glomerular Filtration Rate (GFR) is the amount of filtrate formed by the kidneys per minute. In a healthy individual, the GFR is approximately 125 ml per minute, which translates to 180 liters per day. This rate indicates how well the kidneys are filtering blood, removing waste, and maintaining overall fluid balance in the body.
Explain the autoregulatory mechanism of GFR.
The autoregulation of GFR (glomerular filtration rate) primarily involves the juxta glomerular apparatus (JGA). Here's how it works:
Juxta Glomerular Apparatus (JGA):
The JGA is a specialized region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the point of their contact.
GFR Monitoring:
The JGA continuously monitors the GFR.
Response to Low GFR:
When there's a fall in GFR, the JGA detects this change and activates the juxtaglomerular (JG) cells.
The JG cells release renin, an enzyme.
Renin-Angiotensin System:
Renin converts angiotensinogen (a plasma protein) into angiotensin I.
Angiotensin I is further converted to angiotensin II, a powerful vasoconstrictor.
Increase in GFR:
Angiotensin II causes vasoconstriction of the efferent arteriole, which increases the glomerular blood pressure.
This results in an increase in GFR back to normal levels.
Additional Effects:
Angiotensin II stimulates the release of aldosterone from the adrenal cortex, which increases sodium reabsorption and indirectly increases water reabsorption, contributing further to the regulation of blood pressure and GFR.
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) True. Micturition is controlled by a reflex known as the micturition reflex, which involves the central nervous system (CNS).
(b) False. ADH (antidiuretic hormone) helps in water reabsorption, making the urine more concentrated (hypertonic), not hypotonic.
(c) True. Protein-free fluid is filtered from blood plasma into Bowman's capsule as it is considered a process of ultra-filtration.
(d) True. Henle's loop plays an important role in concentrating the urine by maintaining an osmolarity gradient in the medullary interstitium.
(e) True. Glucose is actively reabsorbed in the proximal convoluted tubule (PCT).
Give a brief account of the counter current mechanism.
The counter current mechanism in the nephron is crucial for the concentration of urine and involves two key structures: the Henle’s loop and the vasa recta.
Henle's Loop: The filtrate flows in opposite directions in the ascending and descending limbs of Henle’s loop. This setup enables the establishment of an osmolarity gradient in the medullary interstitium.
Vasa Recta: These are the capillaries that run parallel to the limbs of Henle’s loop and also have blood flowing in opposite directions in their ascending and descending limbs.
Process:
Descending Limb of Henle's Loop: Permeable to water but almost impermeable to electrolytes, causing water to exit into the interstitium, concentrating the filtrate.
Ascending Limb of Henle's Loop: Impermeable to water but actively and passively transports electrolytes (NaCl) out of the filtrate, diluting it as it ascends.
The proximity of Henle's loop and vasa recta allows for counter current exchange, wherein electrolytes are picked up from the ascending limb of the loop and returned to the deep medulla by the descending vasa recta limb, thus maintaining high osmolarity.
The result is the creation of a medullary interstitial gradient with increasing osmolarity towards the inner medulla, facilitating the reabsorption of water from the collecting ducts and concentrating the urine.
This counter current mechanism enables the kidneys to produce urine that is highly concentrated, conserving water efficiently.
Describe the role of liver, lungs and skin in excretion.
The liver, lungs, and skin play significant roles in the excretion of various wastes:
Liver:
Secretes Bile: The liver produces bile, which contains substances such as bilirubin, biliverdin, cholesterol, and degraded steroid hormones. These substances are eventually eliminated from the body along with digestive wastes.
Lungs:
Remove $\text{CO}_2$: The lungs are responsible for removing large amounts of carbon dioxide (approximately 200 mL/minute) and significant quantities of water every day, which are excreted during respiration.
Skin:
Sweat Glands: The sweat glands produce sweat, a watery fluid containing $\text{NaCl}$, small amounts of urea, and lactic acid. Apart from having a cooling effect on the body surface, sweat also helps in the removal of some excretory wastes.
Sebaceous Glands: These glands secrete sebum, which contains substances such as sterols, hydrocarbons, and waxes. This secretion provides a protective oily covering for the skin but also plays a role in waste elimination.
Together, these organs complement the kidney in maintaining homeostasis by excreting metabolic wastes and excess substances.
Explain micturition.
Micturition
Micturition is the process of releasing urine from the urinary bladder through the urethra to the outside of the body. Here's how it works:
Urine Storage: Urine formed by nephrons is transported to the urinary bladder where it is stored.
Bladder Stretching: As the urinary bladder fills with urine, its walls stretch.
Signal Initiation: The stretch receptors in the bladder walls send signals to the central nervous system (CNS).
CNS Response: The CNS sends motor signals back to the bladder.
Muscle Contraction and Relaxation:
Bladder Contraction: The smooth muscles of the bladder contract.
Urethral Sphincter Relaxation: The urethral sphincter relaxes.
Urine Release: These coordinated actions cause urine to be expelled from the bladder through the urethra.
This whole reflex is called the micturition reflex. On average, an adult human excretes 1 to 1.5 liters of urine per day. The urine is typically light yellow, slightly acidic (pH 6.0), and has a characteristic odor. Various conditions can affect the urine’s characteristics, and its analysis can aid in diagnosing metabolic disorders and kidney malfunctions.
Key points to note:
Voluntary Control: Although the reflex mechanism is mostly involuntary, humans can exercise voluntary control over the timing of micturition.
Stretch Receptors: These are crucial for initiating the micturition reflex by detecting bladder fullness.
CNS Role: The central nervous system coordinates the complex process of muscle contraction and relaxation necessary for micturition.
Match the items of column I with those of column II :
Column I | Column II |
---|---|
(a) Ammonotelism | (i) Birds |
(b) Bowman's capsule | (ii) Water reabsorption |
(c) Micturition | (iii) Bony fish |
(d) Uricotelism | (iv) Urinary bladder |
(e) ADH | (v) Renal tubule |
Column I | Column II |
---|---|
(a) Ammonotelism | (iii) Bony fish |
(b) Bowman's capsule | (v) Renal tubule |
(c) Micturition | (iv) Urinary bladder |
(d) Uricotelism | (i) Birds |
(e) ADH | (ii) Water reabsorption |
What is meant by the term osmoregulation?
Osmoregulation refers to the process by which organisms regulate the water and ion balance in their body to maintain homeostasis. This involves controlling the concentration of electrolytes and ensuring that fluids are distributed effectively within the body, thus maintaining the proper osmolarity of body fluids. In different animals, this process is managed by various excretory structures such as protonephridia, nephridia, malpighian tubules, and the kidneys. In humans, kidneys play a major role in osmoregulation by selective reabsorption and secretion of different substances in the nephron.
Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic, why?
Terrestrial animals are generally either ureotelic or uricotelic and not ammonotelic because ammonia is the most toxic form of nitrogenous waste and requires a large amount of water for its elimination. In terrestrial environments, conserving water is crucial for survival, so animals need to excrete less toxic forms of nitrogenous wastes that require minimal water for excretion. Urea and uric acid are less toxic and can be excreted with lower water loss:
Ureotelic animals (e.g., mammals, many terrestrial amphibians, and marine fishes) excrete nitrogen mainly as urea, which is less toxic and requires less water to be flushed out.
Uricotelic animals (e.g., reptiles, birds, land snails, and insects) excrete nitrogen as uric acid in the form of pellets or paste, which allows for minimal water loss.
What is the significance of juxta glomerular apparatus (JGA) in kidney function?
The juxta glomerular apparatus (JGA) plays a crucial role in the regulation of kidney function. It is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact.
Here is the significance of the JGA:
Regulation of Glomerular Filtration Rate (GFR):
Fall in GFR Response: When there is a fall in the glomerular filtration rate (GFR), the JGA activates the juxta glomerular (JG) cells to release an enzyme called renin.
Renin Release: Renin converts angiotensinogen in the blood to angiotensin I and then to angiotensin II.
Angiotensin II Effects: Angiotensin II is a powerful vasoconstrictor which increases glomerular blood pressure and raises GFR back to normal.
Aldosterone Activation: Angiotensin II also stimulates the adrenal cortex to release aldosterone, which promotes the reabsorption of sodium (Na⁺) and water, further increasing blood pressure and GFR.
Maintenance of Blood Pressure:
The JGA, through the renin-angiotensin-aldosterone system (RAAS), maintains blood pressure. An increase in blood pressure enhances the glomerular filtration rate ensuring effective filtration.
In summary, the JGA is significant for maintaining GFR, balancing blood pressure, and ensuring overall homeostasis within the body.
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) Amphioxus (a cephalochordate animal) has flame cells as excretory structures.
(b) Columns of Bertini are the cortical portions projecting between the medullary pyramids in the human kidney.
(c) Vasa recta is 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 contain all the constituents as in plasma except _____
(d) A healthy adult human excretes (on an average) _____ gm of urea/day.
(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 (Antidiuretic hormone).
(c) Dialysis fluid contain all the constituents as in plasma except nitrogenous wastes.
(d) A healthy adult human excretes (on an average) 25-30 gm of urea/day.
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Ask Chatterbot AINotes - Excretory Products and their Elimination | Class 11 NCERT | Biology
Excretory Products and Their Elimination: Comprehensive Class 11 Notes
Ensuring that our body remains free from harmful substances is crucial for maintaining good health. The process by which animals and humans eliminate metabolic wastes is known as excretion. This article explores the excretory products and their elimination, focusing on the human excretory system, urine formation, and the vital roles other organs play in this essential process.
Human Excretory System
The human excretory system is designed to efficiently remove waste products from the body. It consists of several key components:
Kidneys: Bean-shaped organs situated near the dorsal inner wall of the abdominal cavity.
Ureters: Tubes that carry urine from the kidneys to the urinary bladder.
Urinary bladder: A storage organ for urine.
Urethra: A tube that expels urine from the bladder out of the body.
Urine Formation
Urine formation in humans involves several intricate processes within the nephrons, the functional units of the kidneys. Each kidney houses approximately one million nephrons.
Glomerular Filtration
Glomerular filtration is the first step in urine formation. It occurs in the glomerulus, where blood pressure forces the filtration of blood through the glomerular capillaries into the Bowman's capsule. This process filters out almost all constituents of plasma except proteins, creating what is known as the filtrate.
Tubular Reabsorption and Secretion
The filtrate then moves through various sections of the nephron, undergoing reabsorption and secretion:
Proximal Convoluted Tubule (PCT): Reabsorbs nutrients, electrolytes, and water.
Loop of Henle: Concentrates the filtrate as it moves down and dilutes it as it moves up.
Distal Convoluted Tubule (DCT): Further reabsorption and secretion to maintain ionic balance.
Collecting Duct: Final concentration of urine before it is transported to the renal pelvis.
Mechanism of Concentration of the Filtrate
Mammals have the unique ability to produce concentrated urine. The Loop of Henle and the vasa recta play a crucial role in this process through a counter-current mechanism.
This mechanism involves the opposite flow of filtrate in the loop of Henle and blood in the vasa recta, helping maintain an increasing osmolarity gradient from the cortex to the inner medulla. This gradient facilitates the reabsorption of water from the collecting duct, producing concentrated urine.
Here is a flowchart summarising urine formation stages:
graph TD
A[Blood at afferent arteriole] --> B[Glomerular Filtration]
B --> C[Bowman's Capsule]
C --> D["Proximal Convoluted Tubule (PCT) - Reabsorption"]
D --> E[Loop of Henle - Concentration/Dilution]
E --> F["Distal Convoluted Tubule (DCT) - Reabsorption/Secretion"]
F --> G[Collecting Duct - Final Concentration]
G --> H[Renal Pelvis]
H --> I[Ureter]
I --> J[Urinary Bladder]
J --> K[Urethra - Excretion]
Regulation of Kidney Function
The kidneys' functions are meticulously regulated through hormonal feedback mechanisms involving the hypothalamus, juxtaglomerular apparatus (JGA), and the heart.
Hormonal Controls
Antidiuretic Hormone (ADH): Released by the hypothalamus, ADH facilitates water reabsorption from the distal tubules and collecting ducts, reducing urine volume.
Aldosterone: Secreted by the adrenal cortex, it increases sodium reabsorption in the DCT and collecting ducts, indirectly increasing water reabsorption.
Renin-Angiotensin Mechanism: Activated by the JGA, it increases glomerular blood pressure, enhancing filtration and sodium reabsorption.
Micturition
Micturition, or urination, is the process of expelling urine from the bladder. It is a reflex action controlled by the central nervous system (CNS). The bladder's stretch receptors signal the CNS when full, prompting the smooth muscles of the bladder to contract and the urethral sphincter to relax, releasing urine.
Role of Other Organs in Excretion
In addition to the kidneys, the lungs, liver, and skin play significant roles in excretion:
Lungs: Expel carbon dioxide and water vapour.
Liver: Secretes bile containing waste products.
Skin: Sweat glands remove water, salts, and small amounts of nitrogenous wastes.
Disorders of the Excretory System
Several disorders can affect the excretory system:
Uremia: Accumulation of urea in the blood due to kidney dysfunction. It can be treated with haemodialysis, where an artificial kidney filters waste from the blood.
Kidney Stones: Crystallised salts that can cause severe pain and urinary obstruction.
Glomerulonephritis: Inflammation of the glomeruli, impairing kidney function.
By understanding the processes of excretion, the components involved, and the disorders that can arise, we gain insight into how our body maintains internal balance. Regular functioning of these systems ensures that waste products are efficiently removed, contributing to overall health and homeostasis.
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