Digestive System

• Starts from the buccal cavity and ends at the small intestine.
• Starch → Maltose (by Ptyalin)
• Amylase converts starch → soluble sugar
• Lipase converts fats → glycerine + fatty acid
• Lysosomes destroy bacteria
• Chyme → food material

Teeth

• Humans: Diphyodont (2 sets of teeth), Thecodont (fixed in jaw)
• Milk Teeth: 20 (childhood)
• Dental Formula: Incisor 2/2, Canine 1/1, Premolar 2/2, Molar 3/3 = 32 teeth (Heterodont)
• Enamel: hardest part of body (calcium phosphate + carbonate), shiny, outermost part

Tongue & Taste

• Sweet → Front
• Bitter → Near larynx
• Sour → Side
• Salty → Middle

Digestive Tract

• Length: 5–9 m
• Gastric/Digestive Juices: HCL, Renin, Pepsin
• Residual Organs: Caecum & Vermiform Appendix
• Trypsin (small intestine) → proteins & peptones → polypeptides + amino acids
• Large intestine absorbs water from chyme

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Digestive Glands

Salivary Glands

• Secrete saliva (Ptyalin/Amylase)

Liver (Largest Gland: 1.5–2 kg)

• Secretes bile
• Converts glucose → glycogen (blood sugar control)
• Detoxifies blood
• Hormone regulation & cholesterol management

Storage Functions

• Glycogen
• Vitamins: A, D, E, K, B12
• Minerals: Iron, Copper

Other Functions

• Removes old RBCs & pathogens (Kupffer cells)
• Synthesizes fibrinogen protein
• Excess amino acids → ammonia + pyruvic acids
• Ammonia → urea

Pancreas (Mixed/Dual Gland)

• Exocrine: enzymes (trypsin, amylase, lipase)
• Endocrine: hormones (Glucagon, Insulin, Somatostatin [GIS]) from α, β, γ cells of Islets of Langerhans
• Secretion pH: 8–9 (alkaline, neutralizes stomach acid)
• Main pancreatic duct joins bile duct → duodenum

Gallbladder

• Stores bile.

Introduction

The digestive system is responsible for breaking down food into simpler substances so the body can absorb and use nutrients for energy, growth, and repair.
In Bihar, widespread issues like malnutrition, worm infections, and poor sanitation make digestive health a public concern.

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Main Organs of the Human Digestive System

1. Mouth:

   • Digestion begins here with saliva
   • Enzyme salivary amylase breaks down starch
   • Teeth, tongue, and salivary glands assist in mechanical and chemical digestion

2. Esophagus:

   • Carries food to stomach via peristalsis (wave-like motion)

3. Stomach:

   • Stores and mixes food
   • Secretes hydrochloric acid (HCl) and enzyme pepsin to digest proteins
   • Acid kills germs

4. Small Intestine:

   • Major site of digestion and nutrient absorption
   • Enzymes from pancreas and bile from liver aid in digestion
   • Villi increase absorption area

5. Large Intestine:

   • Absorbs water, minerals; forms feces

6. Rectum and Anus:

   • Storage and removal of waste

📝 PYQ (BPSC): Digestion of food is completed in which part? → Small Intestine
📝 Expected MCQ: What enzyme digests protein in the stomach? → Pepsin

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Accessory Organs

• Liver: Produces bile which helps digest fats
• Gallbladder: Stores and releases bile
• Pancreas: Secretes enzymes (lipase, amylase, trypsin) and insulin

📝 Expected MCQ: Bile is stored in which organ? → Gallbladder
📝 Expected MCQ: Which organ secretes insulin? → Pancreas

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Types of Digestion

• Mechanical Digestion: Physical breakdown (e.g., chewing)
• Chemical Digestion: Breakdown by enzymes (e.g., amylase, pepsin)

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Important Digestive Enzymes

📝 Expected MCQ: Which enzyme breaks down fats? → Lipase

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Bihar-Specific Relevance

• Malnutrition: Poor digestion and absorption
• Worm infections: Common in children; affect small intestine
• Liver diseases: Due to contaminated food, alcohol, or hepatitis
• Schemes like Poshan Abhiyaan, Deworming drives, and Janani Suraksha Yojana indirectly support digestive health

📝 Expected MCQ: Which parasite affects digestion in Bihar children? → Worms (e.g., roundworm)

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PYQs + Expected MCQs

📝 PYQ (BPSC): Where is bile produced? → Liver
📝 Expected MCQ: Enzyme that digests starch? → Amylase
📝 Expected MCQ: Food pipe is also called? → Esophagus
📝 Expected MCQ: Major site of nutrient absorption? → Small Intestine
📝 Expected MCQ: HCl is secreted in which organ? → Stomach

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Quick Revision Points

• Starts in mouth → ends at anus
• Enzymes: Amylase, Pepsin, Lipase, Trypsin
• Liver → makes bile; Pancreas → enzymes + insulin
• Small intestine = digestion + absorption
• Bihar: Malnutrition, worms, poor hygiene affect digestion
• Govt programs: Poshan, Deworming, Safe food drives

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Sources Used

• NCERT Class 10 Science – Life Processes
• Lucent GK – Biology Section
• Drishti Science Quick Book
• Ghatna Chakra PYQs – BPSC, Teacher
• Ministry of Health – Poshan Reports
• EduTeria Bihar Health & Hygiene Booklet