Human Physiology – Excretory Products and Their Elimination Quiz - ICSE Class 11 Biology
Free practice quiz: Human Physiology – Excretory Products and Their Elimination (ICSE Class 11 Biology). 39 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
Play all 39 questions freeSample questions
The countercurrent multiplier mechanism in the loop of Henle primarily functions to establish:
- An osmotic gradient in the renal medulla
- Increased glomerular filtration rate
- Decreased tubular reabsorption
- Enhanced secretion of potassium ions
Show answer
Answer: A. An osmotic gradient in the renal medulla
The countercurrent multiplier, involving the descending and ascending limbs of the loop of Henle, actively transports ions out of the ascending limb, creating a progressively increasing osmotic concentration in the renal medulla. This gradient is essential for the subsequent reabsorption of water from the collecting ducts, concentrating urine.
The filtration barrier in the glomerulus consists of three layers: the endothelium of the glomerular capillaries, the basement membrane, and the podocytes. Which component acts as a selective barrier, preventing large proteins from passing through?
- Endothelium of glomerular capillaries
- Basement membrane
- Podocytes (visceral layer of Bowman's capsule)
- All three layers equally
Show answer
Answer: B. Basement membrane
While all three layers contribute to filtration, the glomerular basement membrane is the primary barrier preventing the passage of large proteins (like albumin) due to its composition of negatively charged glycoproteins and collagen fibers. The fenestrated endothelium allows passage of small molecules but blocks blood cells. The filtration slits between the podocytes also contribute to size exclusion.
A substance with a renal clearance equal to the glomerular filtration rate (GFR) is one that is:
- Filtered and partially reabsorbed
- Filtered and completely reabsorbed
- Filtered and not reabsorbed or secreted
- Filtered and actively secreted
Show answer
Answer: C. Filtered and not reabsorbed or secreted
The clearance of a substance represents the volume of plasma that is completely cleared of that substance by the kidneys per unit time. If a substance is only filtered at the glomerulus and neither reabsorbed nor secreted by the tubules, its clearance will be exactly equal to the GFR, as the entire filtered plasma volume is cleared of this substance.
Which part of the nephron is primarily responsible for facultative water reabsorption, meaning it is regulated by ADH?
- Proximal Convoluted Tubule (PCT)
- Loop of Henle
- Distal Convoluted Tubule (DCT) and Collecting Duct
- Glomerulus
Show answer
Answer: C. Distal Convoluted Tubule (DCT) and Collecting Duct
While about 65% of water reabsorption occurs obligatorily in the PCT and loop of Henle, facultative water reabsorption occurs in the DCT and collecting ducts. The permeability of these segments to water is regulated by ADH, allowing the body to fine-tune water balance based on hydration status.
The reabsorption of water in the PCT is driven by:
- Active transport of water molecules.
- The osmotic gradient created by solute reabsorption.
- The electrical potential difference across the tubule wall.
- Diffusion down its concentration gradient.
Show answer
Answer: B. The osmotic gradient created by solute reabsorption.
As solutes (like sodium, glucose, and amino acids) are actively reabsorbed from the tubular fluid in the PCT, the osmolarity of the surrounding interstitial fluid increases, and the osmolarity of the tubular fluid decreases. This osmotic gradient drives the passive movement of water from the tubular lumen into the interstitial fluid and then into the peritubular capillaries.