Life Processes – Human Digestive System and Digestion
Class 10 Science | Chapter 6 | CBSE + Foundation + Competitive Level
🧑🔬 Human Digestive System and Digestion
1. पाचन क्या है? | What is Digestion?
English:
Digestion is the process of breaking down complex, insoluble food substances into simpler, soluble substances that can be absorbed and utilized by the body.
हिन्दी:
पाचन वह प्रक्रिया है जिसमें जटिल और अघुलनशील भोजन पदार्थों को सरल और घुलनशील पदार्थों में परिवर्तित किया जाता है, ताकि शरीर उन्हें अवशोषित करके उपयोग कर सके।
Digestion is the process of breaking down complex, insoluble food substances into simpler, soluble substances that can be absorbed and utilized by the body.
हिन्दी:
पाचन वह प्रक्रिया है जिसमें जटिल और अघुलनशील भोजन पदार्थों को सरल और घुलनशील पदार्थों में परिवर्तित किया जाता है, ताकि शरीर उन्हें अवशोषित करके उपयोग कर सके।
Key Idea:
Large food molecules → Smaller soluble molecules → Absorption → Utilization
मुख्य विचार:
बड़े भोजन अणु → छोटे घुलनशील अणु → अवशोषण → उपयोग
Large food molecules → Smaller soluble molecules → Absorption → Utilization
मुख्य विचार:
बड़े भोजन अणु → छोटे घुलनशील अणु → अवशोषण → उपयोग
2. पाचन की आवश्यकता | Why is Digestion Necessary?
Food contains complex substances such as carbohydrates, proteins and fats. Most of these cannot be directly absorbed in their complex form.
Therefore, digestion converts them into simpler substances.
| Complex Food | Digested Form |
|---|---|
| Carbohydrates / Starch | Simple sugars such as glucose |
| Proteins | Amino acids |
| Fats | Fatty acids + Glycerol |
3. मानव पाचन तंत्र | Human Digestive System
The human digestive system consists of the alimentary canal and associated digestive glands.
मानव पाचन तंत्र में आहार नाल (Alimentary Canal) तथा उससे संबंधित पाचन ग्रंथियाँ शामिल होती हैं।
मानव पाचन तंत्र में आहार नाल (Alimentary Canal) तथा उससे संबंधित पाचन ग्रंथियाँ शामिल होती हैं।
Mouth → Buccal Cavity → Pharynx → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus
मुख → मुखगुहा → ग्रसनी → ग्रासनली → आमाशय → छोटी आंत → बड़ी आंत → मलाशय → गुदा
मुख → मुखगुहा → ग्रसनी → ग्रासनली → आमाशय → छोटी आंत → बड़ी आंत → मलाशय → गुदा
Mouth
→
Oesophagus
→
Stomach
→
Small Intestine
→
Large Intestine
→
Rectum
→
Anus
4. मुखगुहा | Mouth / Buccal Cavity
Digestion begins in the mouth.
The mouth contains teeth, tongue and salivary glands.
Teeth: Cut, tear and grind food.
Tongue: Mixes food with saliva, helps in swallowing and helps in taste.
Salivary glands: Produce saliva containing the enzyme salivary amylase.
Teeth: Cut, tear and grind food.
Tongue: Mixes food with saliva, helps in swallowing and helps in taste.
Salivary glands: Produce saliva containing the enzyme salivary amylase.
Starch
→
Maltose / Simpler Sugars
Salivary Amylase
Salivary Amylase
Exam Point:
Salivary amylase begins the digestion of starch in the mouth.
परीक्षा बिंदु:
लार में उपस्थित सैलिवरी एमाइलेज मुख में स्टार्च के पाचन की शुरुआत करता है।
Salivary amylase begins the digestion of starch in the mouth.
परीक्षा बिंदु:
लार में उपस्थित सैलिवरी एमाइलेज मुख में स्टार्च के पाचन की शुरुआत करता है।
5. दाँत और उनके कार्य | Teeth and Their Functions
| Type of Teeth | Function |
|---|---|
| Incisors | Cutting and biting |
| Canines | Tearing food |
| Premolars | Crushing and grinding |
| Molars | Grinding and crushing |
6. ग्रासनली | Oesophagus
The oesophagus is a muscular tube connecting the pharynx to the stomach.
Food is pushed towards the stomach by rhythmic muscular contractions called peristalsis.
ग्रासनली एक पेशीय नली है जो ग्रसनी को आमाशय से जोड़ती है। भोजन लयबद्ध पेशीय संकुचन क्रमाकुंचन (Peristalsis) द्वारा आमाशय की ओर जाता है।
ग्रासनली एक पेशीय नली है जो ग्रसनी को आमाशय से जोड़ती है। भोजन लयबद्ध पेशीय संकुचन क्रमाकुंचन (Peristalsis) द्वारा आमाशय की ओर जाता है।
7. आमाशय | Stomach
The stomach is a muscular, J-shaped organ. It stores food temporarily and mixes it with gastric juice.
Gastric juice contains hydrochloric acid, pepsin and mucus.
आमाशय एक पेशीय, J-आकार का अंग है। यह भोजन को कुछ समय के लिए संग्रहित करता है तथा उसे जठर रस के साथ मिलाता है। जठर रस में हाइड्रोक्लोरिक अम्ल, पेप्सिन और म्यूकस प्रमुख घटक हैं।
आमाशय एक पेशीय, J-आकार का अंग है। यह भोजन को कुछ समय के लिए संग्रहित करता है तथा उसे जठर रस के साथ मिलाता है। जठर रस में हाइड्रोक्लोरिक अम्ल, पेप्सिन और म्यूकस प्रमुख घटक हैं।
| Component | Function |
|---|---|
| Hydrochloric Acid (HCl) | Provides acidic medium and helps activate pepsin; also helps kill many microbes. |
| Pepsin | Begins digestion of proteins into smaller peptides. |
| Mucus | Protects the stomach lining from acid and digestive enzymes. |
Important:
HCl does not directly digest proteins. It creates the acidic medium required for pepsin activity.
HCl does not directly digest proteins. It creates the acidic medium required for pepsin activity.
8. छोटी आंत | Small Intestine
The small intestine is the main site of complete digestion and absorption of digested nutrients.
It receives digestive juices from the pancreas and intestinal glands, and bile from the liver.
छोटी आंत पाचन की पूर्णता और पचे हुए पोषक पदार्थों के अवशोषण का मुख्य स्थान है। इसमें अग्न्याशय और आंतों से पाचक रस तथा यकृत से पित्त पहुँचता है।
छोटी आंत पाचन की पूर्णता और पचे हुए पोषक पदार्थों के अवशोषण का मुख्य स्थान है। इसमें अग्न्याशय और आंतों से पाचक रस तथा यकृत से पित्त पहुँचता है।
9. पित्त रस | Bile
Bile is produced by the liver and stored in the gall bladder.
It helps in the digestion of fats mainly by emulsifying fats into tiny droplets, increasing the surface area for lipase action.
Bile also helps provide an alkaline medium for intestinal digestion.
पित्त रस का निर्माण यकृत में होता है और यह पित्ताशय में संग्रहित रहता है। यह वसा को छोटी-छोटी बूंदों में विभाजित करके वसीय पायसीकरण (Emulsification) करता है, जिससे लाइपेज की क्रिया अधिक प्रभावी होती है।
पित्त रस का निर्माण यकृत में होता है और यह पित्ताशय में संग्रहित रहता है। यह वसा को छोटी-छोटी बूंदों में विभाजित करके वसीय पायसीकरण (Emulsification) करता है, जिससे लाइपेज की क्रिया अधिक प्रभावी होती है।
Remember:
Liver → Produces bile
Gall bladder → Stores and concentrates bile
Bile → Helps in fat digestion by emulsification
Liver → Produces bile
Gall bladder → Stores and concentrates bile
Bile → Helps in fat digestion by emulsification
10. अग्न्याशय | Pancreas
The pancreas secretes pancreatic juice containing enzymes that help digest carbohydrates, proteins and fats.
अग्न्याशय पैंक्रियाटिक रस का स्राव करता है जिसमें कार्बोहाइड्रेट, प्रोटीन और वसा के पाचन में सहायता करने वाले एंजाइम होते हैं।
अग्न्याशय पैंक्रियाटिक रस का स्राव करता है जिसमें कार्बोहाइड्रेट, प्रोटीन और वसा के पाचन में सहायता करने वाले एंजाइम होते हैं।
| Pancreatic Enzyme | Main Action |
|---|---|
| Pancreatic amylase | Acts on starch/carbohydrates |
| Trypsin | Acts on proteins/peptides |
| Lipase | Acts on fats |
11. आंतों का रस | Intestinal Juice
Intestinal glands secrete intestinal juice containing enzymes that complete the digestion of carbohydrates, proteins and other food components.
आंतों की ग्रंथियाँ आंतों के रस का स्राव करती हैं। इसके एंजाइम कार्बोहाइड्रेट और प्रोटीन आदि के पाचन को पूर्ण करने में सहायता करते हैं।
आंतों की ग्रंथियाँ आंतों के रस का स्राव करती हैं। इसके एंजाइम कार्बोहाइड्रेट और प्रोटीन आदि के पाचन को पूर्ण करने में सहायता करते हैं।
12. कार्बोहाइड्रेट का पाचन | Digestion of Carbohydrates
| Location | Major Event |
|---|---|
| Mouth | Salivary amylase begins starch digestion. |
| Stomach | Little carbohydrate digestion because acidic conditions inhibit salivary amylase. |
| Small Intestine | Pancreatic and intestinal enzymes complete digestion into simple sugars. |
Starch → Maltose / Smaller Sugars → Glucose
13. प्रोटीन का पाचन | Digestion of Proteins
| Location | Major Event |
|---|---|
| Stomach | Pepsin begins protein digestion. |
| Small Intestine | Pancreatic and intestinal proteases continue and complete digestion. |
Proteins → Peptides → Amino Acids
14. वसा का पाचन | Digestion of Fats
Bile emulsifies fats into smaller droplets. Lipase then breaks fats into fatty acids and glycerol.
पित्त वसा को छोटी बूंदों में विभाजित करता है। इसके बाद लाइपेज वसा को वसीय अम्ल और ग्लिसरॉल में तोड़ता है।
पित्त वसा को छोटी बूंदों में विभाजित करता है। इसके बाद लाइपेज वसा को वसीय अम्ल और ग्लिसरॉल में तोड़ता है।
Fats
→ Emulsification
→ Fatty Acids + Glycerol
15. आंतों की विल्ली | Villi
The inner lining of the small intestine contains numerous finger-like projections called villi.
Villi greatly increase the surface area available for absorption of digested food.
Each villus contains blood capillaries and a lymph vessel called a lacteal.
छोटी आंत की आंतरिक सतह पर अंगुलीनुमा उंगली जैसी संरचनाएँ विल्ली (Villi) होती हैं। ये अवशोषण के लिए सतह क्षेत्र को बहुत बढ़ाती हैं। प्रत्येक विल्ली में रक्त केशिकाएँ और लैक्टियल नामक लसीका वाहिका होती है।
छोटी आंत की आंतरिक सतह पर अंगुलीनुमा उंगली जैसी संरचनाएँ विल्ली (Villi) होती हैं। ये अवशोषण के लिए सतह क्षेत्र को बहुत बढ़ाती हैं। प्रत्येक विल्ली में रक्त केशिकाएँ और लैक्टियल नामक लसीका वाहिका होती है।
Exam Point:
Villi increase the surface area for efficient absorption of digested nutrients.
Villi increase the surface area for efficient absorption of digested nutrients.
16. बड़ी आंत | Large Intestine
The large intestine mainly absorbs water and some salts from the remaining material.
The remaining waste is stored in the rectum and is eventually expelled through the anus.
बड़ी आंत मुख्यतः शेष पदार्थ से जल और कुछ लवणों का अवशोषण करती है। बचा हुआ अपशिष्ट मलाशय में संग्रहित होता है और अंततः गुदा द्वारा बाहर निकाला जाता है।
बड़ी आंत मुख्यतः शेष पदार्थ से जल और कुछ लवणों का अवशोषण करती है। बचा हुआ अपशिष्ट मलाशय में संग्रहित होता है और अंततः गुदा द्वारा बाहर निकाला जाता है।
17. पाचन ग्रंथियाँ | Digestive Glands
| Gland / Organ | Secretion | Main Role |
|---|---|---|
| Salivary glands | Saliva | Begins starch digestion |
| Gastric glands | Gastric juice | Protein digestion and acidic medium |
| Liver | Bile | Fat emulsification |
| Pancreas | Pancreatic juice | Digestion of carbohydrates, proteins and fats |
| Intestinal glands | Intestinal juice | Completes digestion |
18. भोजन की पूरी यात्रा | Complete Journey of Food
Ingestion
→
Mouth
→
Oesophagus
→
Stomach
→
Small Intestine
→
Absorption
→
Large Intestine
→
Egestion
19. अवशोषण और आत्मसातीकरण | Absorption and Assimilation
Absorption: Passage of digested nutrients from the alimentary canal into blood or lymph.
Assimilation: Utilization of absorbed nutrients by body cells for energy, growth, repair and other functions.
अवशोषण: पचे हुए पोषक पदार्थों का आहार नाल से रक्त या लसीका में जाना।
आत्मसातीकरण: कोशिकाओं द्वारा अवशोषित पोषक पदार्थों का उपयोग करना।
Assimilation: Utilization of absorbed nutrients by body cells for energy, growth, repair and other functions.
अवशोषण: पचे हुए पोषक पदार्थों का आहार नाल से रक्त या लसीका में जाना।
आत्मसातीकरण: कोशिकाओं द्वारा अवशोषित पोषक पदार्थों का उपयोग करना।
20. मलत्याग | Egestion
Egestion is the removal of undigested food from the alimentary canal through the anus.
It is different from excretion.
मलत्याग वह प्रक्रिया है जिसमें अपचित भोजन को गुदा द्वारा शरीर से बाहर निकाला जाता है। यह उत्सर्जन (Excretion) से अलग प्रक्रिया है।
मलत्याग वह प्रक्रिया है जिसमें अपचित भोजन को गुदा द्वारा शरीर से बाहर निकाला जाता है। यह उत्सर्जन (Excretion) से अलग प्रक्रिया है।
| Egestion | Excretion |
|---|---|
| Removal of undigested food | Removal of metabolic wastes |
| Through anus | Through organs such as kidneys, lungs and skin |
21. Human Digestion – Complete Summary
| Organ | Main Function |
|---|---|
| Mouth | Ingestion, chewing and beginning of starch digestion |
| Oesophagus | Movement of food by peristalsis |
| Stomach | Storage, mixing and beginning of protein digestion |
| Liver | Produces bile |
| Gall bladder | Stores bile |
| Pancreas | Produces pancreatic digestive enzymes |
| Small intestine | Complete digestion and major absorption |
| Large intestine | Absorbs water and salts |
| Rectum | Stores faeces |
| Anus | Expels faeces |
22. MCQs – Multiple Choice Questions
Q1. Digestion is the process of:
A) Breaking complex food into simpler substances
B) Producing oxygen
C) Removing urine
D) Pumping blood
Answer: A) Breaking complex food into simpler substances
Q2. Digestion of starch begins in the:
A) Stomach
B) Mouth
C) Large intestine
D) Rectum
Answer: B) Mouth
Q3. Which enzyme is present in saliva?
A) Pepsin
B) Lipase
C) Salivary amylase
D) Trypsin
Answer: C) Salivary amylase
Q4. Movement of food through the oesophagus occurs by:
A) Diffusion
B) Osmosis
C) Filtration
D) Peristalsis
Answer: D) Peristalsis
Q5. Which acid is present in gastric juice?
A) Hydrochloric acid
B) Sulphuric acid
C) Nitric acid
D) Carbonic acid
Answer: A) Hydrochloric acid
Q6. Which enzyme begins protein digestion in the stomach?
A) Amylase
B) Pepsin
C) Lipase
D) Maltase
Answer: B) Pepsin
Q7. The organ that produces bile is:
A) Pancreas
B) Stomach
C) Liver
D) Small intestine
Answer: C) Liver
Q8. Bile is stored in the:
A) Pancreas
B) Stomach
C) Small intestine
D) Gall bladder
Answer: D) Gall bladder
Q9. The main function of bile in digestion is:
A) Emulsification of fats
B) Digestion of proteins
C) Digestion of starch in the mouth
D) Absorption of glucose
Answer: A) Emulsification of fats
Q10. Which organ secretes pancreatic juice?
A) Liver
B) Pancreas
C) Stomach
D) Gall bladder
Answer: B) Pancreas
Q11. Complete digestion mainly occurs in the:
A) Mouth
B) Oesophagus
C) Small intestine
D) Large intestine
Answer: C) Small intestine
Q12. The finger-like projections in the small intestine are called:
A) Nephrons
B) Alveoli
C) Bronchi
D) Villi
Answer: D) Villi
Q13. The main function of villi is:
A) Increase surface area for absorption
B) Produce bile
C) Store food
D) Produce saliva
Answer: A) Increase surface area for absorption
Q14. Proteins are finally digested into:
A) Fatty acids
B) Amino acids
C) Glucose
D) Glycerol
Answer: B) Amino acids
Q15. Fats are mainly broken down into:
A) Glucose and amino acids
B) Starch and glucose
C) Fatty acids and glycerol
D) Peptides and amino acids
Answer: C) Fatty acids and glycerol
Q16. Which part mainly absorbs water from undigested material?
A) Mouth
B) Stomach
C) Small intestine
D) Large intestine
Answer: D) Large intestine
Q17. The temporary storage of faeces occurs in the:
A) Rectum
B) Stomach
C) Small intestine
D) Oesophagus
Answer: A) Rectum
Q18. Which structure prevents the stomach wall from being damaged by gastric juice?
A) Bile
B) Mucus
C) Saliva
D) Villi
Answer: B) Mucus
Q19. Which substance provides an acidic medium in the stomach?
A) Bile
B) Saliva
C) HCl
D) Pancreatic juice
Answer: C) HCl
Q20. Which organ receives bile and pancreatic juice?
A) Stomach
B) Oesophagus
C) Large intestine
D) Small intestine
Answer: D) Small intestine
Q21. The process of taking food into the body is:
A) Ingestion
B) Absorption
C) Assimilation
D) Egestion
Answer: A) Ingestion
Q22. Passage of digested nutrients into blood or lymph is called:
A) Digestion
B) Absorption
C) Ingestion
D) Egestion
Answer: B) Absorption
Q23. Utilization of absorbed nutrients by cells is called:
A) Digestion
B) Ingestion
C) Assimilation
D) Egestion
Answer: C) Assimilation
Q24. Removal of undigested food is called:
A) Absorption
B) Assimilation
C) Excretion
D) Egestion
Answer: D) Egestion
Q25. Which digestive gland produces saliva?
A) Salivary glands
B) Liver
C) Pancreas
D) Gastric glands
Answer: A) Salivary glands
Q26. Which teeth are mainly used for tearing food?
A) Incisors
B) Canines
C) Molars
D) Premolars
Answer: B) Canines
Q27. Which enzyme digests fats?
A) Pepsin
B) Amylase
C) Lipase
D) Trypsin
Answer: C) Lipase
Q28. Which enzyme helps digest proteins in the small intestine?
A) Amylase
B) Lipase
C) Maltase
D) Trypsin
Answer: D) Trypsin
Q29. Which organ is both a digestive gland and an important metabolic organ?
A) Liver
B) Oesophagus
C) Rectum
D) Teeth
Answer: A) Liver
Q30. Which sequence is correct?
A) Stomach → Mouth → Small intestine → Oesophagus
B) Mouth → Oesophagus → Stomach → Small intestine
C) Mouth → Stomach → Oesophagus → Large intestine
D) Oesophagus → Mouth → Stomach → Small intestine
Answer: B) Mouth → Oesophagus → Stomach → Small intestine
23. Subjective Questions – 1 to 6 Marks
1 Mark
Q1. Define digestion.
Q1. Define digestion.
Digestion is the breakdown of complex food into simpler, soluble substances that can be absorbed and utilized.
1 Mark
Q2. Name the enzyme present in saliva.
Q2. Name the enzyme present in saliva.
Salivary amylase.
1 Mark
Q3. What is peristalsis?
Q3. What is peristalsis?
Peristalsis is the rhythmic muscular movement that pushes food through the alimentary canal.
2 Marks
Q4. What are the functions of saliva?
Q4. What are the functions of saliva?
1. It moistens and lubricates food.
2. Salivary amylase begins the digestion of starch.
2. Salivary amylase begins the digestion of starch.
2 Marks
Q5. What is the role of HCl in the stomach?
Q5. What is the role of HCl in the stomach?
HCl provides an acidic medium required for pepsin activity and also helps kill many microorganisms entering with food.
2 Marks
Q6. What is the function of bile?
Q6. What is the function of bile?
Bile helps emulsify fats into small droplets and contributes to an alkaline medium for digestion in the small intestine.
3 Marks
Q7. State three functions of the stomach.
Q7. State three functions of the stomach.
1. Stores food temporarily.
2. Mixes food with gastric juice.
3. Begins protein digestion through pepsin.
2. Mixes food with gastric juice.
3. Begins protein digestion through pepsin.
3 Marks
Q8. Why is the small intestine important in digestion?
Q8. Why is the small intestine important in digestion?
The small intestine is the main site where digestion is completed. It receives bile, pancreatic juice and intestinal secretions. It also contains villi for efficient absorption of digested nutrients.
3 Marks
Q9. What are villi? State their importance.
Q9. What are villi? State their importance.
Villi are finger-like projections lining the small intestine. They greatly increase the surface area for absorption and contain blood capillaries and lymph vessels to transport absorbed nutrients.
4 Marks
Q10. Explain digestion of carbohydrates in humans.
Q10. Explain digestion of carbohydrates in humans.
Carbohydrate digestion begins in the mouth where salivary amylase acts on starch. In the stomach, carbohydrate digestion is greatly reduced because the acidic medium inhibits salivary amylase. In the small intestine, pancreatic and intestinal enzymes continue and complete carbohydrate digestion into simple sugars such as glucose.
4 Marks
Q11. Explain digestion of proteins in humans.
Q11. Explain digestion of proteins in humans.
Protein digestion begins in the stomach. HCl provides the acidic medium for pepsin, which begins breaking proteins into smaller peptides. In the small intestine, pancreatic and intestinal proteases continue digestion and convert peptides into simpler substances, ultimately amino acids.
4 Marks
Q12. Explain digestion of fats.
Q12. Explain digestion of fats.
Bile produced by the liver emulsifies fats into small droplets. This increases their surface area. Lipase then acts on the fats and breaks them into fatty acids and glycerol.
5 Marks
Q13. Describe the human alimentary canal.
Q13. Describe the human alimentary canal.
The human alimentary canal is a continuous muscular tube consisting mainly of:
1. Mouth: Ingestion and beginning of starch digestion.
2. Oesophagus: Transports food by peristalsis.
3. Stomach: Stores food and begins protein digestion.
4. Small intestine: Completes digestion and absorbs nutrients.
5. Large intestine: Absorbs water and salts.
6. Rectum: Stores faeces.
7. Anus: Expels faeces.
1. Mouth: Ingestion and beginning of starch digestion.
2. Oesophagus: Transports food by peristalsis.
3. Stomach: Stores food and begins protein digestion.
4. Small intestine: Completes digestion and absorbs nutrients.
5. Large intestine: Absorbs water and salts.
6. Rectum: Stores faeces.
7. Anus: Expels faeces.
5 Marks
Q14. Explain the role of different digestive glands.
Q14. Explain the role of different digestive glands.
Salivary glands: Produce saliva containing salivary amylase.
Gastric glands: Produce HCl, pepsin and mucus.
Liver: Produces bile.
Pancreas: Produces pancreatic juice containing digestive enzymes.
Intestinal glands: Produce intestinal secretions that help complete digestion.
Gastric glands: Produce HCl, pepsin and mucus.
Liver: Produces bile.
Pancreas: Produces pancreatic juice containing digestive enzymes.
Intestinal glands: Produce intestinal secretions that help complete digestion.
6 Marks
Q15. Explain the complete process of digestion in humans from mouth to anus.
Q15. Explain the complete process of digestion in humans from mouth to anus.
1. Mouth: Food is chewed and mixed with saliva. Salivary amylase begins starch digestion.
2. Oesophagus: Food moves towards the stomach through peristalsis.
3. Stomach: Food is mixed with gastric juice. HCl creates an acidic medium and pepsin begins protein digestion. Mucus protects the stomach lining.
4. Small intestine: Bile emulsifies fats. Pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats.
5. Absorption: Villi absorb digested nutrients into blood and lymph.
6. Large intestine and anus: Water is absorbed, faeces are stored in the rectum and finally expelled through the anus.
2. Oesophagus: Food moves towards the stomach through peristalsis.
3. Stomach: Food is mixed with gastric juice. HCl creates an acidic medium and pepsin begins protein digestion. Mucus protects the stomach lining.
4. Small intestine: Bile emulsifies fats. Pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats.
5. Absorption: Villi absorb digested nutrients into blood and lymph.
6. Large intestine and anus: Water is absorbed, faeces are stored in the rectum and finally expelled through the anus.
6 Marks
Q16. Draw/describe the pathway of food through the human digestive system and mention the main function of each part.
Q16. Draw/describe the pathway of food through the human digestive system and mention the main function of each part.
Mouth → Pharynx → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus
| Part | Main Function |
|---|---|
| Mouth | Chewing and initial starch digestion |
| Oesophagus | Peristaltic movement |
| Stomach | Storage and protein digestion |
| Small Intestine | Complete digestion and absorption |
| Large Intestine | Water and salt absorption |
| Rectum | Temporary storage of faeces |
| Anus | Egestion |
24. HOTS – Higher Order Thinking Questions
Q17. Why does digestion not occur in the oesophagus?
The main function of the oesophagus is to transport food from the pharynx to the stomach by peristalsis. It does not contain major digestive glands responsible for significant digestion.
Q18. Why is bile important even though it does not contain a digestive enzyme?
Bile emulsifies fats into tiny droplets, increasing the surface area available for lipase action. It also helps provide a suitable alkaline medium for intestinal digestion.
Q19. Why are villi numerous and finger-like?
Their large number and finger-like shape greatly increase the surface area available for absorption of digested nutrients.
Q20. Why is mucus important in the stomach?
Mucus forms a protective layer over the stomach lining and helps protect it from hydrochloric acid and digestive enzymes.
25. Quick Revision – परीक्षा के लिए महत्वपूर्ण बिंदु
🧠 Mouth → Chewing + Saliva + Starch digestion
🧠 Oesophagus → Peristalsis
🧠 Stomach → HCl + Pepsin + Mucus + Protein digestion
🧠 Liver → Produces bile
🧠 Gall bladder → Stores bile
🧠 Pancreas → Pancreatic digestive enzymes
🧠 Small intestine → Complete digestion + major absorption
🧠 Villi → Increase absorption surface area
🧠 Large intestine → Water and salt absorption
🧠 Rectum → Stores faeces
🧠 Anus → Egestion
🧠 Oesophagus → Peristalsis
🧠 Stomach → HCl + Pepsin + Mucus + Protein digestion
🧠 Liver → Produces bile
🧠 Gall bladder → Stores bile
🧠 Pancreas → Pancreatic digestive enzymes
🧠 Small intestine → Complete digestion + major absorption
🧠 Villi → Increase absorption surface area
🧠 Large intestine → Water and salt absorption
🧠 Rectum → Stores faeces
🧠 Anus → Egestion
26. Master Revision Table
| Food Component | Major End Product of Digestion |
|---|---|
| Carbohydrates | Simple sugars such as glucose |
| Proteins | Amino acids |
| Fats | Fatty acids + Glycerol |
27. CBSE Exam Golden Points
- Digestion converts complex food into simpler absorbable substances.
- Digestion of starch begins in the mouth.
- Salivary amylase is present in saliva.
- Peristalsis moves food through the alimentary canal.
- Pepsin begins protein digestion in the stomach.
- HCl provides the acidic medium in the stomach.
- Mucus protects the stomach lining.
- Liver produces bile.
- Gall bladder stores bile.
- Bile emulsifies fats.
- Pancreas secretes pancreatic juice.
- Small intestine is the main site of complete digestion and absorption.
- Villi increase the surface area for absorption.
- Large intestine mainly absorbs water and some salts.
- Egestion is different from excretion.
28. One-Line Master Revision
Mouth → Starch Digestion
→ Oesophagus → Peristalsis
→ Stomach → Protein Digestion
→ Small Intestine → Complete Digestion + Absorption
→ Large Intestine → Water Absorption
→ Rectum → Storage
→ Anus → Egestion
