Excretory Products and their Elimination MCQs for NEET – Page 5

Question 41 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Analyze the osmotic characteristics of the loop of Henle’s descending limb:

I. It is highly permeable to water.
II. It is almost impermeable to electrolytes.
III. Its permeability properties cause the filtrate to get diluted as it flows down.
IV. Active transport of sodium ions occurs in this segment.

Statements I and II are correct because the descending limb is permeable to water but nearly impermeable to electrolytes. Statement III is incorrect because loss of water concentrates the filtrate rather than diluting it. Statement IV is incorrect because active sodium transport occurs in the ascending limb, not the descending limb.

Question 42 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Examine these statements about the transport properties of the loop of Henle’s ascending limb:

I. It is highly permeable to water, allowing rapid osmotic outflow.
II. It allows active or passive transport of electrolytes into the medullary fluid.
III. As the concentrated filtrate passes upward, it gets diluted.
IV. Reabsorption is maximum in this segment of the loop.

Statement I is incorrect because the ascending limb is impermeable to water. Statements II and III are correct because electrolytes leave the ascending limb while water cannot, causing dilution of the filtrate. Statement IV is incorrect because reabsorption is minimum in the ascending limb compared with other nephron segments.

Question 43 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Study the transport mechanisms operating in the Distal Convoluted Tubule (DCT):

I. Reabsorption of Na⁺ and water in this segment is conditional and regulated by hormones.
II. The DCT is incapable of reabsorbing bicarbonate ions (HCO₃^-).
III. DCT cells selectively secrete sodium and calcium ions to maintain blood pH.
IV. The segment helps maintain the sodium-potassium balance in the blood.

Statement I is correct because Na⁺ and water reabsorption in the DCT is hormonally regulated. Statement II is incorrect because the DCT reabsorbs bicarbonate ions. Statement III is incorrect because the DCT selectively secretes H⁺, K⁺, and NH₃, not sodium and calcium. Statement IV is correct because the DCT maintains sodium-potassium balance in the blood.

Question 44 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Consider the functional significance of the kidney's collecting duct:

I. It is a long duct extending from the renal cortex down into the inner medulla.
II. Under hormonal influence, large amounts of water can be reabsorbed from this segment to concentrate urine.
III. It allows small amounts of urea to enter the medullary interstitium to maintain high osmolarity.
IV. It is completely impermeable to all ions, preventing any tubular secretion of H⁺ and K⁺.

Statements I, II and III are correct. The collecting duct extends from the cortex into the inner medulla, reabsorbs large amounts of water under ADH influence, and permits small amounts of urea to diffuse into the medullary interstitium to maintain osmolarity. Statement IV is incorrect because the collecting duct participates in pH and ionic balance by secreting H⁺ and K⁺ ions.

Question 45 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Evaluate the foundational elements of the renal counter current mechanism:

I. The loop of Henle and vasa recta play a major role in concentrating the filtrate.
II. The flow of filtrate in the two limbs of Henle's loop is in opposite directions.
III. Blood flow in the two limbs of the vasa recta occurs in the same direction as the filtrate in Henle's loop.
IV. Proximity between Henle's loop and vasa recta is essential for the concentration mechanism to work.

Statements I, II and IV are correct. The loop of Henle and vasa recta constitute the counter current mechanism, opposite flow in Henle's loop forms the counter current, and their close proximity maintains the medullary osmotic gradient. Statement III is incorrect because blood in the vasa recta also flows in a counter current pattern.

Question 46 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Examine the solute concentration gradient in the renal medullary interstitium:

I. Osmolarity increases from 300 mOsmol/L in the cortex to 1200 mOsmol/L in the inner medulla.
II. This steep gradient is established primarily by sodium chloride (NaCl) and urea.
III. Glomerular blood pressure is the primary driver of this interstitial osmolarity gradient.
IV. The gradient helps in the passive movement of water out of the collecting duct.

Statements I, II and IV are correct. The osmotic gradient rises from about 300 mOsmol/L in the cortex to about 1200 mOsmol/L in the inner medulla and is maintained mainly by NaCl and urea. This gradient facilitates passive water reabsorption from the collecting duct. Statement III is incorrect because the gradient is established by the counter current mechanism rather than glomerular blood pressure.

Question 47 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Study the specific transport steps of NaCl and urea in the counter current mechanism:

I. NaCl is transported out by the ascending limb of Henle's loop and exchanged into the descending limb of vasa recta.
II. NaCl is returned to the medullary interstitium by the ascending portion of the vasa recta.
III. Small amounts of urea enter the thick ascending limb and are stored there permanently.
IV. Urea enters the thin ascending limb of Henle's loop and is recycled back to the medulla by the collecting tubule.

Statements I, II and IV are correct. NaCl leaves the ascending limb of Henle's loop, enters the descending limb of the vasa recta, and returns to the medullary interstitium via the ascending vasa recta. Urea is recycled through the thin ascending limb and collecting tubule. Statement III is incorrect because urea is recycled rather than permanently stored.

Question 48 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Evaluate the hormonal regulation of renal water conservation by ADH:

I. Hypothalamic osmoreceptors are activated by an increase in blood volume or body fluid volume.
II. Excessive fluid loss stimulates the neurohypophysis to release Antidiuretic Hormone (ADH).
III. ADH acts primarily on the PCT to increase active transport of water.
IV. An increase in body fluid volume completes the feedback loop by switching off osmoreceptors and suppressing ADH.

Statement I is incorrect because osmoreceptors are activated mainly by decreased body fluid volume or increased osmolarity. Statement II is correct because dehydration stimulates ADH release from the neurohypophysis. Statement III is incorrect because ADH acts mainly on the DCT and collecting duct to increase water reabsorption. Statement IV is correct because increased body fluid volume suppresses osmoreceptor activity and ADH release.

Question 49 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Analyze the hormonal cascade of the Renin-Angiotensin-Aldosterone System (RAAS):

I. A fall in glomerular blood pressure or GFR triggers JG cells to release renin.
II. Renin enzymatically converts angiotensinogen in the blood into angiotensin I.
III. Angiotensin II is a powerful vasodilator that lowers systemic blood pressure.
IV. Angiotensin II stimulates the adrenal cortex to secrete aldosterone.

Statements I, II and IV are correct. Reduced GFR stimulates renin release, renin converts angiotensinogen to angiotensin I, and angiotensin II stimulates aldosterone secretion from the adrenal cortex. Statement III is incorrect because angiotensin II is a powerful vasoconstrictor that raises blood pressure.

Question 50 of 100

📘 CLASS XI

Excretory Products And Their Elimination

Consider the action and regulation of Atrial Natriuretic Factor (ANF) and Aldosterone:

I. Aldosterone causes reabsorption of sodium ions and water from the distal parts of the renal tubule.
II. Aldosterone action leads to a decrease in systemic blood pressure and GFR.
III. Increased blood flow to the heart's atria triggers the release of Atrial Natriuretic Factor (ANF).
IV. ANF causes vasodilation, which decreases blood pressure, acting as a check on the renin-angiotensin mechanism.

Statements I, III and IV are correct. Aldosterone promotes Na⁺ and water reabsorption, increased atrial stretch stimulates ANF release, and ANF lowers blood pressure through vasodilation while opposing the renin-angiotensin mechanism. Statement II is incorrect because aldosterone increases rather than decreases blood pressure and GFR.