7. In a nephron, _____ follows the ascending limb of the “loop of Henle”.

(A) Descending limb

(B) Distal tubule

(D) Proximal tubule

Distal Convoluted Tubule Follows the Ascending Limb of Loop of Henle

Introduction

The nephron is the structural and functional unit of the kidney responsible for filtering blood, maintaining electrolyte balance, regulating body fluid volume, controlling blood pressure, and eliminating metabolic waste products. Each human kidney contains nearly one million nephrons that work continuously to produce urine while maintaining the body’s internal environment. The nephron performs its functions through filtration, selective reabsorption, secretion, and concentration of urine.

A nephron consists of the renal corpuscle and a renal tubule. The renal tubule includes the proximal convoluted tubule (PCT), the descending limb of the Loop of Henle, the ascending limb of the Loop of Henle, the distal convoluted tubule (DCT), and finally the collecting duct.

Correct Answer

Correct Option: (B) Distal Tubule

Detailed Explanation

The renal tubule follows a definite anatomical sequence that begins with the proximal convoluted tubule (PCT), continues through the descending limb of the Loop of Henle, then the ascending limb of the Loop of Henle, followed by the distal convoluted tubule (DCT), and finally drains into the collecting tubule or collecting duct.

After filtrate passes through the ascending limb, it enters the distal convoluted tubule. The DCT is responsible for fine regulation of sodium, potassium, calcium, hydrogen ions, and bicarbonate under hormonal control. Hormones such as aldosterone, parathyroid hormone (PTH), and antidiuretic hormone (ADH) influence transport processes in this region, allowing the kidney to precisely regulate electrolyte balance and acid-base homeostasis.

Therefore, the nephron segment immediately following the ascending limb of the Loop of Henle is the distal convoluted tubule.

Explanation of Each Option

Option (A): Descending Limb

This statement is incorrect. The descending limb precedes the ascending limb and is highly permeable to water but relatively impermeable to sodium and chloride ions. Water leaves the filtrate by osmosis, concentrating the tubular fluid as it descends into the renal medulla.

Option (B): Distal Tubule

This statement is correct. The distal convoluted tubule directly follows the ascending limb of the Loop of Henle. It participates in selective reabsorption of sodium and calcium, secretion of potassium and hydrogen ions, and regulation of electrolyte balance under hormonal influence.

Option (C): Collecting Tubule

This statement is incorrect. The collecting tubule or collecting duct receives filtrate from the distal convoluted tubule. Although it is the next structure after the DCT, it does not immediately follow the ascending limb.

Option (D): Proximal Tubule

This statement is incorrect. The proximal convoluted tubule is the first tubular segment after Bowman’s capsule. It is responsible for reabsorbing nearly 65–70% of filtered water and solutes before the filtrate enters the Loop of Henle.

Why Option (B) is Correct

The ascending limb of the Loop of Henle empties directly into the distal convoluted tubule. This segment plays a vital role in regulating electrolyte composition, acid-base balance, and blood pressure through hormone-mediated transport processes.

Why the Other Options are Incorrect

Why Option (A) is Incorrect

The descending limb is located before the ascending limb in the nephron sequence.

Why Option (C) is Incorrect

The collecting tubule receives filtrate only after it has passed through the distal convoluted tubule.

Why Option (D) is Incorrect

The proximal convoluted tubule is the earliest part of the renal tubule immediately following Bowman’s capsule.

Comparison of All Options

Option	Nephron Segment	Position Relative to Ascending Limb	Correct or Incorrect
A	Descending Limb	Before ascending limb	Incorrect
B	Distal Convoluted Tubule	Immediately after ascending limb	Correct
C	Collecting Tubule	After distal tubule	Incorrect
D	Proximal Convoluted Tubule	First tubular segment	Incorrect

Correct Sequence of Nephron Segments

Order	Nephron Structure	Main Function
1	Bowman’s Capsule	Ultrafiltration of blood
2	Proximal Convoluted Tubule (PCT)	Bulk reabsorption of water, glucose, amino acids and ions
3	Descending Limb of Loop of Henle	Water reabsorption
4	Ascending Limb of Loop of Henle	Reabsorption of Na⁺, K⁺ and Cl⁻; impermeable to water
5	Distal Convoluted Tubule (DCT)	Fine regulation of electrolytes and acid-base balance
6	Collecting Duct	Final urine concentration under ADH

Functions of Major Nephron Segments

Segment	Primary Function
Proximal Convoluted Tubule	Maximum reabsorption of filtrate
Descending Limb	Water reabsorption
Ascending Limb	Salt reabsorption without water
Distal Convoluted Tubule	Hormonal regulation of ions
Collecting Duct	Final adjustment of urine concentration

Biological Significance of the Distal Convoluted Tubule

The distal convoluted tubule is responsible for the fine adjustment of urine composition. It selectively reabsorbs sodium and calcium while secreting potassium and hydrogen ions. Aldosterone increases sodium reabsorption and potassium secretion, whereas parathyroid hormone enhances calcium reabsorption. These regulatory mechanisms help maintain electrolyte balance, blood pressure, blood pH, and overall body fluid homeostasis.

Competitive Examination Perspective

Nephron structure and urine formation are among the highest-yield topics in Human Physiology. Students should remember the correct sequence of nephron segments: Bowman’s capsule → Proximal Convoluted Tubule → Descending Limb → Ascending Limb → Distal Convoluted Tubule → Collecting Duct. They should also understand the permeability characteristics and physiological functions of each segment, as these concepts are repeatedly examined in CSIR NET, GATE, DBT BET, ICMR JRF, ICAR, NEET PG, and university entrance examinations.

Final Answer