Human Digestive System MCQs— Class 6 Science MCQs

Quick Revision: Human Digestive System

• Digestion: The process of breaking down complex food into simple, absorbable substances so the body can utilise them.
• Alimentary Canal: The long tube from mouth to anus through which food passes. Parts: Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus.
• Mouth: Teeth (chewing — mechanical digestion), Saliva (contains salivary amylase that breaks down starch into sugar — chemical digestion). Tongue helps mix and push food.
• Oesophagus: Muscular tube that carries food from mouth to stomach. Uses rhythmic contractions called peristalsis.
• Stomach: Muscular bag that churns food. Produces hydrochloric acid (kills germs, creates acidic medium for enzymes), pepsin (digests proteins), and mucus (protects stomach lining).
• Small Intestine: Long coiled tube (about 7 m). Main site of digestion and absorption. Divided into Duodenum, Jejunum, and Ileum.
• Liver: Largest gland in the body. Produces bile (stored in gall bladder) that breaks down fats into droplets (emulsification).
• Pancreas: Produces pancreatic juice containing enzymes that digest carbohydrates, proteins, and fats.
• Villi: Finger-like projections in the inner wall of the small intestine that increase surface area for maximum absorption of nutrients into the blood.
• Large Intestine: Absorbs water and minerals from undigested food. Remaining waste forms faeces.
• Rectum & Anus: Rectum stores faeces temporarily. Anus is the opening through which faeces (egestion) are expelled.
• Nutrients — Carbohydrates: Provide energy (rice, wheat, bread, potatoes). Broken down into glucose.
• Nutrients — Proteins: Body-building foods (pulses, eggs, meat, milk). Broken down into amino acids.
• Nutrients — Fats: Provide energy and warmth (butter, oil, nuts). Broken down into fatty acids and glycerol.
• Vitamins & Minerals: Protective foods needed in small amounts for proper body functioning (fruits, vegetables).
• Roughage (Dietary Fibre): Indigestible plant material that helps in bowel movement and prevents constipation.
• Water: Essential for digestion, absorption, and transport of nutrients. The body loses water through urine, sweat, and breath.
• Balanced Diet: Food containing all nutrients (carbohydrates, proteins, fats, vitamins, minerals, roughage, water) in the right proportions.
• Malnutrition: Deficiencies caused by lack of one or more nutrients over a long period (e.g., scurvy — vitamin C, rickets — vitamin D, anaemia — iron).