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Q.158 Zoology ⭐ 360° Option Elimination Active
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NEET 2023 Zoology Question 158 Solution

Topic: Digestion and Absorption · Official NTA Booklet Code G5
NEET 2023 Zoology Question 158: Gastrointestinal Valves: Ileo-caecal Valve

Question

Once the undigested and unabsorbed substances enter the caecum, their backflow is prevented by-

  1. (1)Pyloric sphincter
  2. (2)Sphincter of Oddi
  3. (3)Ileo - caecal valve
  4. (4)Gastro - oesophageal sphincter
✓
Verified Against NTA Final Answer Key
Option (3) : Ileo - caecal valve
📚 Digestion and Absorption Easy
📋 Given Parameters & Problem Setup
Substance Undigested and unabsorbed faecal matter
Site of Entry Caecum of large intestine
Protective Action Prevention of backflow into ileum
⚡

The 30-Second Exam Hall Shortcut: ⚡ Anatomical Junction Anchor: Ileum to Caecum = Ileo-caecal Valve

⏱️ Save ~20 seconds

The junction between the terminal small intestine (ileum) and the initial large intestine (caecum) is guarded by the Ileo-caecal valve, which prevents the retrograde backflow of faecal matter!

1 Gastro-oesophageal sphincter: Regulates passage of food from oesophagus into stomach.
2 Pyloric sphincter: Regulates chyme emptying from stomach into duodenum.
3 Sphincter of Oddi: Guards the opening of the hepato-pancreatic duct into duodenum.
4 Ileo-caecal valve: Prevents backflow from caecum into ileum.
5 Match Option (3) Ileo - caecal valve.
🛡️
Why You Can 100% Trust This Shortcut: Canonical NCERT Human Physiology alimentary tract sphincters and valves inventory.
📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Anatomy of the Ileo-Caecal Junction

The small intestine terminates at the ileum, which opens into the blind pouch-like caecum of the large intestine:

Terminal Ileum→Ileo-caecal ValveCaecum  ⟹  One-way passage preventing backflow\text{Terminal Ileum} \xrightarrow{\mathbf{\text{Ileo-caecal Valve}}} \text{Caecum} \implies \text{One-way passage preventing backflow}
Step 2

Verbatim NCERT Reference

NCERT states verbatim: "The undigested, unabsorbed substances called faeces enters into the caecum of the large intestine through ileo-caecal valve, which prevents the back flow of the faecal matter."

Step 3

Evaluation of Distractor Sphincters

Gastro-oesophageal sphincter guards the cardiac stomach. Pyloric sphincter guards the gastroduodenal junction. Sphincter of Oddi guards the ampulla of Vater (hepato-pancreatic duct).

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan
1 1
✗ Incorrect
Verdict & Scientific Reason:

Guards the opening between the pyloric stomach and duodenum.

⚠️
Student Fallacy (Why candidates pick this trap): Confusing gastroduodenal junction with ileocaecal junction.
2 2
✗ Incorrect
Verdict & Scientific Reason:

Guards the hepato-pancreatic duct opening into the C-shaped duodenum.

⚠️
Student Fallacy (Why candidates pick this trap): Confusing biliary/pancreatic sphincters with intestinal valves.
3 3
✓ 100% Correct
Verdict & Scientific Reason:

Verbatim NCERT: the ileo-caecal valve prevents backflow of faecal matter from caecum into ileum.

💡
Why this is airtight: None; textbook verbatim.
4 4
✗ Incorrect
Verdict & Scientific Reason:

Guards the cardiac opening between the oesophagus and stomach to prevent acid reflux.

⚠️
Student Fallacy (Why candidates pick this trap): Confusing upper digestive sphincters with lower intestinal valves.
⚠️

NTA Trap Alert: Valve vs. Sphincter Functional Distinction

Students frequently confuse true muscular sphincters (like pyloric and gastro-oesophageal sphincters) with mucosal flap valves (the ileo-caecal valve).

🛡️ How to avoid the -1 mark: Ileum + Caecum = Ileo-caecal valve (the only valve named after these two structures).
📖

Core NEET Syllabus Standard

NCERT Biology · Digestion and Absorption Standard Benchmark
Core Scientific Principle Tested:

"Undigested substances enter the caecum of the large intestine through the ileo-caecal valve, which prevents the back flow of the faecal matter."

Syllabus Focus: Alimentary Canal
✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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