Digestive System
ICSE · Class 9 · Biology
Quick revision notes for Digestive System — ICSE Class 9 Biology. Key concepts, formulas, and definitions for last-minute revision.
Key Topics to Revise
Introduction to Digestion and Enzymes
- Digestion is the breakdown of food into soluble, absorbable form
- Food must be converted into smaller molecules to pass through cell membranes
- Enzymes are protein catalysts that speed up digestion reactions
Structure of Teeth and Dental Formula
- Adult humans have 32 permanent teeth of 4 different types
- Incisors (4 per jaw) - cutting and biting with chisel-like edges
- Canines (2 per jaw) - holding and tearing, conical and pointed
Structure of a Tooth
- Each tooth has a crown (exposed part) and root (embedded in jaw)
- Enamel covers the crown - hardest substance in the body
- Dentine forms the bulk of the tooth - harder than bone but softer than enamel
Salivary Glands and Saliva
- Three pairs of salivary glands: parotid, submandibular, sublingual
- Saliva is slightly acidic (pH 6.8) containing 99% water, salts, mucus, and ptyalin
- Daily saliva production: 1000-1500 ml
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What are the important topics in Digestive System for ICSE Class 9 Biology?
Digestive System covers several key topics that are frequently asked in ICSE Class 9 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Digestive System — ICSE Class 9 Biology?
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