Human Digestive System – Class 10 Biology (Life Processes)
Introduction
The human body requires food to obtain energy for survival, growth, repair, and functioning of organs. The process of breaking down complex food into simple, absorbable substances is called digestion. The human digestive system is a complex series of organs and glands designed to process food, extract nutrients, and eliminate waste. This topic is an important part of the Class 10 NCERT Biology Chapter – Life Processes, and several questions from this section are frequently asked in CBSE Board Exams.
We'll Cover Class 10 NCERT - Chapter 5: Life Processes, specifically Nutrition Topic: Human Digestive System with Notes, Diagrams, flowcharts, and important questions.
The Human Digestive System – Overview
The digestive system consists of the alimentary canal (gut) and associated glands. Together, they ensure ingestion, digestion, absorption, assimilation, and egestion of food.
Steps of Nutrition in Humans:
- Ingestion – The process of taking food inside the body.
- Digestion – Breaking complex food into simple soluble molecules.
- Absorption – Passage of digested food into blood or lymph.
- Assimilation – Utilisation of absorbed food for energy, growth, and repair.
- Egestion – Removal of undigested waste.
Structure of Human Digestive System
- Digestion begins in the mouth.
- Teeth break food into smaller pieces (mechanical digestion).
- Saliva, secreted by salivary glands, contains salivary amylase enzyme that converts starch into maltose (chemical digestion).
- Tongue helps in mixing food with saliva and swallowing.
2. Pharynx and Oesophagus
- The pharynx connects the mouth to the oesophagus.
- Oesophagus (food pipe) pushes food into the stomach through muscular contractions called peristalsis.
3. Stomach
- J-shaped muscular organ.
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Gastric glands secrete:
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Hydrochloric acid (HCl): Makes medium acidic, kills germs.
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Pepsin enzyme: Breaks proteins into peptones.
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Mucus: Protects stomach lining from acid.
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- Food becomes a semi-digested paste called chyme.
4. Small Intestine
- Longest part of alimentary canal (~6 meters).
- Three regions: duodenum, jejunum, ileum.
- Digestive glands associated:
- Liver: Produces bile juice, stored in gall bladder. Bile emulsifies fats (breaks into small droplets).
- Pancreas: Produces pancreatic juice containing amylase (carbohydrate digestion), trypsin (protein digestion), and lipase (fat digestion).
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Enzymes of the small intestine (intestinal juice) complete digestion:
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Carbohydrates → glucose
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Proteins → amino acids
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Fats → fatty acids and glycerol
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Absorption of nutrients occurs through finger-like projections called villi, which increase surface area.
5. Large Intestine
- Absorbs water and salts from undigested food.
- The remaining waste forms faeces.
6. Rectum and Anus
- Rectum stores faeces temporarily.
- Anus helps in egestion of faecal matter.
Digestive Juices and Enzymes – Quick Table
| Digestive Juice | Secreted By | Enzymes | Function |
|---|---|---|---|
| Saliva | Salivary glands | Amylase | Starch → Maltose |
| Gastric juice | Stomach | Pepsin, HCl | Proteins → Peptones; acidic medium |
| Bile | Liver (stored in gall bladder) | – | Emulsifies fats |
| Pancreatic juice | Pancreas | Amylase, Trypsin, Lipase | Carbs → Glucose, Proteins → Amino acids, Fats → Fatty acids & glycerol |
| Intestinal juice | Small intestine | Maltase, Peptidase, Lipase | Completes digestion of food |
Key Features of Digestion
- Digestion is both mechanical (teeth, churning in stomach) and chemical (enzymes, bile, acids).
- Maximum digestion and absorption occurs in the small intestine.
- Undigested material is excreted through the anus.
.png "Human Digestive System Class 10 Biology | Flowchart")
Additional Information (Beyond NCERT)
- The liver is the largest gland in the human body.
- The pancreas acts as both an endocrine (secretes insulin) and exocrine gland (secretes digestive enzymes).
- Villi contain blood capillaries and lymph vessels (lacteals)
for absorption of nutrients. - Peristalsis is an involuntary process regulated by smooth muscles.
Previous Year Questions (PYQs) – Human Digestive System
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(CBSE 2019) Name the enzyme present in saliva and state its function.
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Answer: Salivary amylase; converts starch into maltose.
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(CBSE 2020) Why is the small intestine longer in herbivores than in carnivores?
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Answer: Herbivores eat cellulose-rich food which takes longer to digest, hence longer small intestine.
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(CBSE 2018) Why does the stomach secrete hydrochloric acid?
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Answer: HCl provides acidic medium for pepsin action and kills harmful microbes.
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(CBSE 2022) What is the function of bile? Where is it produced and stored?
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Answer: Bile emulsifies fats. Produced in liver, stored in gall bladder.
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Important Questions for Practice
- Define peristalsis. Where does it occur?
- Name three enzymes secreted by the pancreas and their functions.
- Explain the role of villi in the small intestine.
- State one difference between mechanical and chemical digestion.
- Why is digestion of food essential for the body?
- What will happen if bile is not secreted?
Summary Notes – Human Digestive System
- Human nutrition involves ingestion, digestion, absorption, assimilation, and egestion.
- Organs: mouth, oesophagus, stomach, small intestine, large intestine, rectum, anus.
- Associated glands: salivary glands, liver, pancreas.
- Enzymes: amylase, pepsin, trypsin, lipase, etc.
- Most digestion and absorption occurs in the small intestine.
- Bile has no enzyme but helps in fat digestion.
- The process ensures supply of glucose, amino acids, fatty acids, glycerol, vitamins, and minerals for growth and energy.
Conclusion
The human digestive system is one of the most important life processes in Class 10 Biology. A clear understanding of the structure, enzymes, and functions helps students answer both short and long questions in board exams. Practising PYQs and important questions given above will further strengthen exam preparation.
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