Find the best tutors and institutes for Class 11 Tuition
Q4:
Give a brief account of the counter current mechanism.
Solution :
1. Theoretical Foundation of Counter-Current Mechanism
The counter-current mechanism is a sophisticated physiological process occurring within the nephrons of the mammalian kidney, specifically involving the Loop of Henle and the Vasa Recta. Its primary biological objective is to maintain a high osmotic gradient in the medullary interstitium, which facilitates the concentration of urine [Per the Principle of Osmoregulation].
2. Structural Arrangement & Directional Flow
The efficiency of this system relies on the anatomical orientation of the loops:
- Loop of Henle: The flow of filtrate in the descending limb is opposite to the flow in the ascending limb.
- Vasa Recta: These capillary networks run parallel to the Loop of Henle, where blood flows in a direction counter to the filtrate flow in the adjacent loop.
3. Sequential Mechanism of Gradient Maintenance
The gradient is established via the following steps:
- Active Transport of Solutes: The ascending limb of the Loop of Henle is impermeable to water but actively transports $NaCl$ into the medullary interstitium. [Per Active Transport kinetics].
- Osmotic Equilibrating: This transport increases the osmolarity of the interstitial fluid, which draws water out of the descending limb via osmosis.
- The Multiplier Effect: As more $NaCl$ is transported, the osmolarity of the medulla increases (reaching up to $1200 \, mOsm/L$ in the inner medulla), effectively "multiplying" the concentration gradient.
- Vasa Recta Role: The blood flow in the vasa recta is sluggish, preventing the washout of the $NaCl$ gradient. Instead, the vasa recta undergoes a counter-current exchange, retaining solutes in the medulla while removing excess water reabsorbed from the tubules.
4. Summary of Gradient Dynamics
| Structure | Permeability Characteristics | Function |
|---|---|---|
| Descending Limb | Permeable to water, Impermeable to $NaCl$ | Concentration of filtrate |
| Ascending Limb | Impermeable to water, Active transport of $NaCl$ | Maintenance of medullary salinity |
| Vasa Recta | Freely permeable to water and solutes | Prevention of gradient dissipation |
Final Solution: The counter-current mechanism, sustained by the counter-current multiplier of the Loop of Henle and the counter-current exchanger of the Vasa Recta, is the fundamental physiological process that generates and preserves the medullary osmotic gradient, allowing mammals to produce concentrated, hypertonic urine and minimize water loss.
More Questions from Class 11 Biology Excretory Products and Elimination EXERCISES
- Q1: Define Glomerular Filtration Rate (GFR)
- Q2: Explain the autoregulatory mechanism of GFR.
- Q3(a): Indicate whether the following statements are true or false : (a) Micturition is carried out by a reflex.
- Q3(b): Indicate whether the following statements are true or false : (b) ADH helps in water elimination, making the urine hypotonic.
- Q3(c): Indicate whether the following statements are true or false : (c) Protein-free fluid is filtered from blood plasma into the Bowman’s capsule.
- Q3(d): Indicate whether the following statements are true or false : (d) Henle’s loop plays an important role in concentrating the urine.
- Q3(e): Indicate whether the following statements are true or false : (e) Glucose is actively reabsorbed in the proximal convoluted tubule.
- Q5: Describe the role of liver, lungs and skin in excretion.
- Q6: Explain micturition.
- Q7: 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
- Q8: What is meant by the term osmoregulation?
- Q9: Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic, why ?
- Q10: What is the significance of juxta glomerular apparatus (JGA) in kidney function?
- Q11(a): Name the following: (a) A chordate animal having flame cells as excretory structures
- Q11(b): Name the following: (b) Cortical portions projecting between the medullary pyramids in the human kidney
- Q11(c): Name the following: (c) A loop of capillary running parallel to the Henle’s loop.
- Q12(a): Fill in the gaps : (a) Ascending limb of Henle’s loop is _______ to water whereas the descending limb is _______ to it.
- Q12(b): Fill in the gaps : (b) Reabsorption of water from distal parts of the tubules is facilitated by hormone _______.
- Q12(c): Fill in the gaps : (c) Dialysis fluid contain all the constituents as in plasma except _______.
- Q12(d): Fill in the gaps : (d) A healthy adult human excretes (on an average) _______ gm of urea/day.
CBSE Solutions for Class 11 Biology Excretory Products and Elimination
Chapters in CBSE - Class 11 Biology
- The Living World
- Biological Classification
- Plant Kingdom
- Animal Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Structural Organisation in Animals
- Cell – The Unit of Life
- Biomolecules
- Cell Cycle and Division
- Transport in Plants
- Mineral Nutrition
- Photosynthesis
- Respiration in Plants
- Plant Growth and Development
- Digestion and Absorption
- Breathing and Exchange of Gases
- Body Fluids and Circulation
- Locomotion and Movement
- Neural Control and Coordination
- Chemical Coordination and Integration
Top Tutors who teach Excretory Products and Elimination
Top Tutor
Besa, Nagpur
8 yrs of
Exp
10 hrs of classes completed
2000
per hour
Student's Home
Tutor's home
I believe in learning,When I am teaching I get a dual opportunity of learning as well as teaching. I always synthesis more on Power of Thinking, Which is followed by the act. I have experience conducting training sessions For the professionals as well the students. When I was in school,I have won prizes in many debate Competitions. I always motivate people to achieve their real dreams.
Super Tutor
H C Sarani, Kolkata
18 yrs of
Exp
9 students
2071 hrs of classes completed
500
per hour
Online Classes
Tutor's home
Students of 11th standard faces major challenges in three segments: 1) Boolean Algebra & Logic Gates 2) Developing the programming logic and 3) Database Management System 4) Java/ Python
I am very thankful to sir for making all the conceps clear and taught in a very fruitful way. Thank you so much sir. Highly satisfied.
Top Tutor
Dilshad Garden, Delhi
4 yrs of
Exp
3 students
967 hrs of classes completed
260
per hour
Online Classes
I am a Chartered Accountant by profession and have been teaching Commerce subjects—primarily Accounting and Economics—for the past 4 years. I work with BCom/BSc students and CA aspirants, helping them build strong conceptual clarity and practical understanding. Teaching is my passion and hobby, and I focus on delivering quality education by maintaining small group sizes (2–3 students at a time). This allows me to give individual attention, ensuring that every student understands the concepts thoroughly and gains confidence. My teaching approach is practical-based, designed to bridge the gap between academic theories and real-world industry applications. I emphasize how concepts are applied in actual business environments—both in private and public sectors—so students can connect textbook knowledge to real scenarios. I prefer conducting online, individual sessions to provide personalized support and address each student’s learning style and pace. I teach using a whiteboard for clear and visual explanations. For CA students, I recommend specific books aligned with the syllabus. For Class 11 and 12, I rely on their existing school books but provide additional notes or references on request to avoid overloading them. While I haven't pursued awards in teaching, the positive feedback from my students and their academic success bring me immense satisfaction. My goal is to make learning effective, relevant, and engaging for every student I teach.
Top Tutor
Govindpuri Shiva Colony, Jaipur
10 yrs of
Exp
7 students
1729 hrs of classes completed
500
per hour
Online Classes
Tutor's home
Experience of 10 years
Good teaching style and has well knowledge about his subject. Sir is very punctual about time and study
Top Tutor
West Marredpally, Hyderabad
20 yrs of
Exp
1 student
127 hrs of classes completed
500
per hour
Online Classes
Student's Home
Tutor's home
I love to teach physics for classes 11th and 12th. Solve numericals and explain the concepts clearly to students. I emphasize understanding of the concepts clearly and then attempt solving ot numericals.
Other Subjects in CBSE - Class 11
Download free CBSE - Class 11 Biology Excretory Products and Elimination EXERCISES worksheets
Download Now
