Correct answer: ✅ D) Nephron
Let’s go step by step and clarify why the nephron is the correct choice and why the others are not.
🧠 Core concept
The kidney performs three essential functions to form urine:
1. Filtration
2. Reabsorption
3. Secretion
👉 The single structural and functional unit that carries out all three processes together is the nephron.
🔬 Why Nephron is correct
A nephron is a complete working unit of the kidney and consists of:
1️⃣ Renal corpuscle
Glomerulus Bowman’s capsule
Site of filtration
2️⃣ Renal tubule
Proximal tubule: bulk reabsorption (Na⁺, glucose, amino acids, water)
Loop of Henle: urine concentration
Distal tubule & collecting duct: fine-tuning via reabsorption and secretion
✔️ Therefore, filtration reabsorption secretion all occur within the nephron.
❌ Why the other options are wrong
A) Glomerulus ❌
Performs filtration only
Does not handle reabsorption or secretion
It is just one part of the nephron
B) Medulla ❌
A region of the kidney
Contains loops of Henle and collecting ducts
Not a functional unit by itself
C) Cortex ❌
Another anatomical region
Contains glomeruli and convoluted tubules
Still not a functional unit
📌 High-yield comparison
StructureFunction
GlomerulusFiltration only
CortexKidney region
MedullaKidney region
NephronFiltration Reabsorption Secretion ✅
📝 Exam pearl
> The nephron is the smallest unit capable of performing all kidney functions.
✅ Final Answer:
D) Nephron