ANAND CLASSES Study Material and Notes to explore about the process of nutrition in human beings with detailed explanation of the human digestive system for Class 10 Science with detailed Q&A, assertion-reason based MCQs, and explanations. Perfect for CBSE, NEET, and school exam preparation.
🧬 Nutrition in Human Beings (Human Digestive System)
📘 Introduction
Nutrition is the process by which living organisms obtain and utilize food for growth, energy, and maintenance. In human beings, this complex process takes place through the digestive system, which involves mechanical and chemical breakdown of food into simpler forms.
🏛️ Human Digestive System: Overview
The human digestive system comprises:
- Alimentary Canal: A muscular tube about 9 meters long, extending from mouth to anus. The ducts of various glands open into the alimentary canal and pour the secretions of the digestive juices into the alimentary canal
- Associated Glands: Salivary glands, liver, and pancreas.
🔗 Sequence of Organs in Alimentary Canal:
- Mouth
- Oesophagus (Food Pipe)
- Stomach
- Small Intestine
- Large Intestine
🧪 Associated Digestive Glands:
- Salivary glands: Secrete saliva.
- Liver: Secretes bile (stored in gall bladder).
- Pancreas: Secretes pancreatic juices.
🔄 Steps of Nutrition in Humans
1️⃣ Ingestion
- Process of taking food into the mouth.
- Humans use hands to place food in the mouth.
2️⃣ Digestion
Digestion begins in the mouth and continues in the stomach and small intestine.
📌 In the Mouth:
- Contains teeth, tongue, and salivary glands.
- Teeth: Cut and grind food → Physical digestion.
- Saliva (from salivary glands): Contains amylase (enzyme) that breaks down starch into sugar → Chemical digestion. Thus, the digestion of starch (carbohydrate) begins in the mouth itself. Since the food remains in the mouth only for a short time, so the digestion of food remains incomplete in mouth.
- Tongue: Mixes saliva with food and helps in swallowing.
📌 In the Oesophagus:
- No digestion occurs here.
- Peristaltic movement: Rhythmic contractions of muscles push food toward the stomach.
The slightly digested food in the mouth is swallowed by the tongue and goes down the food pipe called oesophagus (see Figure). The oesophagus carries food to the stomach.
This happens as follows : The walls of food pipe have muscles which can contract and expand alternately. When the slightly digested food enters the food pipe, the walls of food pipe start contraction and expansion movements. The contraction and expansion movement of the walls of food pipe is called peristaltic movement.
This peristaltic movement of food pipe (or oesophagus) pushes the slightly digested food into the stomach (In fact, the peristaltic movement moves the food in all the digestive organs throughout the alimentary canal).
📌 In the Stomach:
- A J-shaped organ with gastric glands secreting:
- Hydrochloric Acid (HCl) – Makes the medium acidic and kills bacteria.
- Pepsin – Breaks proteins into smaller molecules.
- Mucus – Protects stomach lining from acid.
The stomach is a J-shaped organ present on the left side of the abdomen (see Figure). The food is further digested in the stomach. The food is churned in the stomach for about three hours. During this time, the food breaks down into still smaller pieces and forms a semi-solid paste. The stomach wall contains three tubular glands in its walls.
The glands present in the walls of the stomach secrete gastric juice. The gastric juice contains three substances : hydrochloric acid, the enzyme pepsin and mucus. Due to the presence of hydrochloric acid, the gastric juice is acidic in nature. In the acidic medium, the enzyme pepsin begins the digestion of proteins present in food to form smaller molecules. Thus, the protein digestion begins in the stomach.
Please note that the protein digesting enzyme pepsin is active only in the presence of an acid. So, function of hydrochloric acid in the stomach is to make the medium of gastric juice acidic so that the enzyme pepsin can digest the proteins properly. Another function of hydrochloric acid is that it kills any bacteria which may enter the stomach with food. The mucus helps to protect the stomach wall from its own secretions of hydrochloric acid. If mucus is not secreted, hydrochloric acid will cause the erosion of inner lining of stomach leading to the formation of ulcers in the stomach. The partially digested food then goes from the stomach into the small intestine. The exit of food from stomach is regulated by a ‘sphincter muscle’ which releases it in small amounts into the small intestine.
📌 In the Small Intestine:
- Longest part (~6.5 m) of the digestive tract.
- Digestion completes here with help of:
- Bile (from liver) – Emulsifies fats, neutralizes acid.
- Pancreatic Juice (from pancreas) – Contains:
- Amylase (carbohydrates → sugar),
- Trypsin (proteins → peptides),
- Lipase (fats → fatty acids + glycerol).
- Intestinal Juice – Completes digestion.
From the stomach, the partially digested food enters the small intestine. The small intestine is the largest part of the alimentary canal. It is about 6.5 metres long in an adult man. Though the small intestine is very long, it is called small intestine because it is very narrow. The small intestine is arranged in the form of a coil in our belly (see Figure). Please note that the length of the small intestine differs in various animals depending on the type of food they eat. For example, cellulose is a carbohydrate food which is digested with difficulty. So, the herbivorous animals like cow which eat grass need a longer ‘small intestine’ to allow the cellulose present in grass to be digested completely. On the other hand, meat is a food which is easier to digest. So, the carnivorous animals like tigers which eat meat have a shorter ‘small intestine’.
The small intestine in human beings is the site of complete digestion of food (like carbohydrates, proteins and fats). This happens as follows :
Fig.2 Pancreas secretes pancreatic juice into the small intestine which contains three digestive enzymes : pancreatic
amylase, trypsin and lipase.
Fih.3 Liver secretes bile into the small intestine. We can also see the gall bladder in this picture which stores bile.
(a) The small intestine receives the secretions of two glands : liver and pancreas. Liver secretes bile Bile is a greenish yellow liquid made in the liver which is normally stored in the gall bladder. Bile is alkaline, and contains salts which help to emulsify or break the fats (or lipids) present in the food. Thus, bile performs two functions :
(i) makes the acidic food coming from the stomach alkaline so that pancreatic enzymes can act on it, and
(ii) bile salts break the fats present in the food into small globules making it easy for the enzymes to act and digest them.
Pancreas is a large gland which lies parallel to and beneath the stomach (see Figure). Pancreas secretes pancreatic juice which contains digestive enzymes like pancreatic amylase, trypsin and lipase. The enzyme amylase breaks down the starch, the enzyme trypsin digests the proteins and the enzyme lipase breaks down the emulsified fats.
(b) The walls of small intestine contain glands which secrete intestinal juice. The intestinal juice contains a number of enzymes which complete the digestion of complex carbohydrates into glucose, proteins into amino acids and fats into fatty acids and glycerol. Glucose, amino acids, fatty acids and glycerol are small, water soluble molecules. In this way, the process of digestion converts the large and insoluble food molecules into small, water soluble molecules. The chemical digestion of food is brought about by biological catalysts called enzymes.
3️⃣ Absorption
- Occurs in Small Intestine through villi.
- Digested food (glucose, amino acids, fatty acids) diffuses into blood via capillaries in villi.
- Adaptation: Large surface area due to millions of villi.
After digestion, the molecules of food become so small that they can pass through the walls of the small intestine (which contain blood capillaries) and go into our blood. This is called absorption. The small intestine is the main region for the absorption of digested food.
In fact, the small intestine is especially adapted for absorbing the digested food. The inner surface of small intestine has millions of tiny, fingerlike projections called villi. The presence of villi gives the inner walls of the small intestine a very large surface area. And the large surface area of small intestine helps in the rapid absorption of digested food. The digested food which is absorbed through the walls of the small intestine, goes into our blood.
4️⃣ Assimilation
- Absorbed nutrients are:
- Transported to all body cells.
- Used for energy (via cellular respiration), growth, and repair.
- Excess glucose is stored in the liver as glycogen.
The blood carries digested and dissolved food to all the parts of the body where it becomes assimilated as part of the cells. This assimilated food is used by the body cells for obtaining energy as well as for growth and repair of the body. The energy is released by the oxidation of assimilated food in the cells during respiration. The digested food which is not used by our body immediately is stored in the liver in the form of a carbohydrate called ‘glycogen’. This stored glycogen can be used as a source of energy by the body as and when required.
5️⃣ Egestion
- Undigested food passes into large intestine.
- Water is absorbed, and semi-solid waste is stored in rectum.
- Waste is expelled as faeces through anus.
- Controlled by anal sphincter.
A part of the food which we eat cannot be digested by our body. This undigested food cannot be absorbed in the small intestine. So, the undigested food passes from the small intestine into a wider tube called large intestine (see Figure) (It is called large intestine because it is a quite wide tube). The walls of large intestine absorb most of the water from the undigested food (with the help of villi). Due to this, the undigested part of food becomes almost solid.
The last part of the large intestine called ‘rectum’ stores this undigested food for some time. And when we go to the toilet, then this undigested food is passed out (or egested) from our body through anus as faeces or ‘stool’ (see Figure). The act of expelling the faeces is called egestion or defecation. The exit of faeces is controlled by the anal sphincter.
🧪 Sample Experiment: Action of Saliva on Starch
Problem: 1 mL of very dilute starch solution (1% starch solution) is taken in a test-tube and 1 mL of saliva is added to it. After keeping this mixture for half an hour, a few drops of dilute iodine solution are added to the test-tube. There is no change in colour on adding iodine solution. What does this
tell you about the action of saliva on starch
Conclusion: When a mixture of dilute starch solution and saliva is kept in a test-tube for half an hour, it does not produce a blue-black colour with iodine solution showing that no starch is left in the test-tube. This tells us that the action of saliva has broken down starch into some other substance which does not give any colour with iodine solution. Actually, saliva contains an enzyme ‘amylase’ which converts starch into a sugar.
🦷 Dental Caries
- Tooth Structure:
- Enamel → The hard, outer covering of a tooth is called enamel. Hardest substance in body. It is harder than even bones
- Dentine → The part of tooth below enamel is called dentine. Similar to bone.
- Pulp → Inside the dentine is pulp cavity. The pulp cavity contains nerves and blood vessels. The formation of small cavities (or holes) in the teeth due to the action of acid-forming bacteria and improper
- dental care is called dental caries.
🦠 Causes of Dental Caries:
- Sugary food + bacteria → Acids
- Acids dissolve enamel → cavities
- Can lead to infection, toothache.
When we eat sugary food, the bacteria in our mouth act on sugar to produce acids. These acids first dissolve the calcium salts from the tooth enamel and then from dentine forming small cavities (or holes) in the tooth over a period of time.
The formation of cavities reduces the distance between the outside of the tooth and the pulp cavity which contains nerves and blood vessels. The acids produced by bacteria irritate the nerve endings inside the tooth and cause toothache. If the cavities caused by dental decay are not cleaned and filled by a dentist, the bacteria will get into the pulp cavity of tooth causing inflammation and infection leading to severe pain.
🧼 Prevention:
- Brush regularly to remove plaque (sticky layer of bacteria + food).
- Prevents acid formation and decay.
If the teeth are not cleaned regularly, they become covered with a sticky, yellowish layer of food particles and bacteria cells called ‘dental plaque’. Since plaque covers the teeth forming a layer over them, the alkaline saliva cannot reach the tooth surface to neutralise the acid formed by bacteria and hence tooth decay sets in. Brushing the teeth regularly, after eating food, removes the plaque before bacteria produces acids. This will prevent dental caries or tooth decay
🧬 Nutrition in Human Beings (Human Digestive System) : Questions and Answers
Important Exam Oriented Questions and Answers based on the topic Nutrition in Human Beings (Human Digestive System), suitable for Class 10 Science (Biology)
🔹 1. What is nutrition in human beings and which system carries it out?
Answer:
Nutrition in human beings refers to the process of taking in food and utilizing it for growth, energy, and repair of the body. This is carried out by the human digestive system, which includes the alimentary canal and associated digestive glands.
🔹 2. What are the main components of the human digestive system?
Answer:
The human digestive system comprises:
- Alimentary Canal: Mouth, Oesophagus (food pipe), Stomach, Small Intestine, Large Intestine.
- Associated Glands: Salivary Glands, Liver, Pancreas.
🔹 3. What is the length and function of the human alimentary canal?
Answer:
The alimentary canal is about 9 metres long. Its function is to digest food and absorb nutrients, with digestive juices from glands being secreted into it.
📘 STEPS OF NUTRITION IN HUMANS:
🔸 4. What is ingestion and how does it occur in humans?
Answer:
Ingestion is the intake of food. In humans, it occurs through the mouth using hands.
🔸 5. Where does digestion begin and what organs are involved initially?
Answer:
Digestion begins in the mouth. The organs involved are:
- Teeth: Cut, chew, and grind food (physical digestion).
- Tongue: Mixes food with saliva.
- Salivary Glands: Secrete saliva containing salivary amylase, an enzyme that begins the digestion of starch into sugar.
🔸 6. What is the role of saliva in digestion?
Answer:
- Moistens food to make it easy to swallow.
- Contains the enzyme salivary amylase which breaks down starch into sugar (chemical digestion).
🔸 7. What is peristalsis?
Answer:
Peristalsis is the wave-like contraction and relaxation of muscles in the walls of the alimentary canal that pushes food forward, especially through the oesophagus to the stomach.
🔸 8. What happens to food in the stomach?
Answer:
In the stomach:
- Food is churned and mixed for about 3 hours.
- Gastric juice is secreted, which contains:
- Hydrochloric acid: Kills bacteria, makes medium acidic.
- Pepsin (enzyme): Begins protein digestion.
- Mucus: Protects the stomach lining from acid.
🔸 9. What controls the movement of food from stomach to small intestine?
Answer:
A sphincter muscle at the end of the stomach regulates the exit of partially digested food into the small intestine.
🔸 10. What is the function of the small intestine in digestion?
Answer:
The small intestine is the site of complete digestion and absorption of food. It receives:
- Bile from the liver – emulsifies fats and neutralizes acid.
- Pancreatic juice from pancreas – contains amylase, trypsin, lipase to digest carbohydrates, proteins, and fats.
- Intestinal juice – completes digestion of all nutrients into glucose, amino acids, fatty acids, and glycerol.
🔸 11. How does absorption take place in the small intestine?
Answer:
Absorption occurs through villi (finger-like projections) which:
- Increase surface area.
- Contain blood vessels that absorb digested nutrients into the bloodstream.
🔸 12. What is assimilation?
Answer:
Assimilation is the process where absorbed nutrients are:
- Transported by the blood to body cells.
- Used for energy production, growth, and repair.
- Excess glucose is stored in the liver as glycogen.
🔸 13. What is egestion?
Answer:
Egestion is the removal of undigested food. The undigested part:
- Moves to the large intestine.
- Water is absorbed.
- Stored in the rectum as faeces.
- Expelled through the anus (controlled by the anal sphincter).
🧪 Sample Problem Q&A
🔸 14. A test-tube contains starch and saliva. After 30 minutes, iodine is added but no blue-black colour appears. Why?
Answer:
The absence of blue-black colour shows that starch is no longer present. This indicates that the salivary enzyme amylase has converted starch into sugar, which does not react with iodine.
🦷 Dental Health
🔸 15. What are dental caries and how are they formed?
Answer:
Dental caries are cavities in teeth caused by:
- Bacteria converting sugar into acids.
- Acids dissolve enamel and dentine.
- Leads to pain if they reach the pulp cavity with nerves.
🔸 16. What is dental plaque and how can it be prevented?
Answer:
Dental plaque is a sticky yellowish layer of bacteria and food on teeth. It:
- Prevents saliva from neutralizing acids.
- Promotes tooth decay.
- Can be prevented by regular brushing after eating.
❓ FAQs
Q1. Where does protein digestion begin in humans?
A: In the stomach, by the enzyme pepsin in the presence of HCl.
Q2. What is peristalsis?
A: It is the wave-like muscle movement that pushes food along the digestive tract.
Q3. What is the function of bile?
A: Neutralizes acidic food and emulsifies fats for easier digestion.
Q4. What is assimilation?
A: It is the process where absorbed food is used for energy, growth, and repair.
📝 MCQs on Nutrition in Human Beings
Multiple Choice Questions (MCQs) based on the topic Nutrition in Human Beings (Human Digestive System), suitable for Class 10 Science (Biology).
1. Which part of the digestive system is responsible for the complete digestion of food?
A. Stomach
B. Mouth
C. Small Intestine
D. Large Intestine
Answer: C. Small Intestine
Explanation: The small intestine is where the complete digestion of carbohydrates, proteins, and fats occurs with the help of enzymes from liver and pancreas.
2. What is the function of bile juice in digestion?
A. Digests proteins
B. Makes food acidic
C. Emulsifies fats
D. Breaks down starch
Answer: C. Emulsifies fats
Explanation: Bile juice emulsifies fats, breaking them into smaller globules, making it easier for enzymes to act.
3. Which enzyme in saliva helps in digestion of starch?
A. Lipase
B. Pepsin
C. Trypsin
D. Amylase
Answer: D. Amylase
Explanation: Salivary amylase converts starch into simple sugars in the mouth.
4. What prevents the stomach lining from being damaged by hydrochloric acid?
A. Mucus
B. Enzymes
C. Water
D. Bile
Answer: A. Mucus
Explanation: Mucus coats the stomach lining and protects it from the corrosive action of HCl.
5. Which movement pushes the food through the oesophagus?
A. Emulsification
B. Peristalsis
C. Respiration
D. Digestion
Answer: B. Peristalsis
Explanation: Peristalsis is the wave-like muscular movement that pushes food down the oesophagus.
6. In which part of the alimentary canal is the food mixed with bile juice?
A. Stomach
B. Mouth
C. Small Intestine
D. Large Intestine
Answer: C. Small Intestine
Explanation: Bile juice from the liver is released into the small intestine to emulsify fats.
7. The inner lining of small intestine has:
A. Cilia
B. Microtubules
C. Villi
D. Hair
Answer: C. Villi
Explanation: Villi increase the surface area for absorption of digested food into the bloodstream.
8. Trypsin enzyme digests which nutrient?
A. Fats
B. Carbohydrates
C. Proteins
D. Vitamins
Answer: C. Proteins
Explanation: Trypsin, released by the pancreas, digests proteins into amino acids.
9. What is the pH nature of gastric juice in the stomach?
A. Neutral
B. Slightly basic
C. Acidic
D. Alkaline
Answer: C. Acidic
Explanation: Gastric juice contains HCl, making it acidic for activation of enzymes like pepsin.
10. Which part of the digestive system absorbs water from undigested food?
A. Small Intestine
B. Liver
C. Rectum
D. Large Intestine
Answer: D. Large Intestine
Explanation: The large intestine absorbs water and forms solid feces from undigested food.
11. The function of sphincter muscle between stomach and small intestine is to:
A. Absorb nutrients
B. Prevent regurgitation
C. Regulate food release
D. Mix bile juice
Answer: C. Regulate food release
Explanation: The sphincter muscle controls the passage of food from stomach to small intestine.
12. Lipase enzyme is responsible for digesting:
A. Starch
B. Fats
C. Proteins
D. Vitamins
Answer: B. Fats
Explanation: Lipase converts fats into fatty acids and glycerol in the small intestine.
13. The process of removal of undigested food from the body is called:
A. Assimilation
B. Egestion
C. Absorption
D. Ingestion
Answer: B. Egestion
Explanation: Egestion is the expulsion of undigested food through the anus.
14. Which gland produces both endocrine and digestive (exocrine) secretions?
A. Salivary gland
B. Pancreas
C. Liver
D. Kidney
Answer: B. Pancreas
Explanation: Pancreas secretes insulin (endocrine) and digestive enzymes (exocrine) like amylase and trypsin.
15. Which nutrient begins its digestion in the mouth?
A. Proteins
B. Fats
C. Carbohydrates
D. Vitamins
Answer: C. Carbohydrates
Explanation: Salivary amylase starts the digestion of starch (a carbohydrate) in the mouth.
🔍 Assertion and Reason Based Questions
Assertion-Reason type questions on the topic Nutrition in Human Beings (Class 10 Science) along with correct answers and explanations. These are great for testing analytical thinking and conceptual clarity.
Directions: For each of the following questions, choose the correct option:
A. Both Assertion (A) and Reason (R) are true, and Reason is the correct explanation of Assertion.
B. Both Assertion (A) and Reason (R) are true, but Reason is not the correct explanation of Assertion.
C. Assertion (A) is true, but Reason (R) is false.
D. Assertion (A) is false, but Reason (R) is true.
Q1.
Assertion (A): Bile juice emulsifies fats.
Reason (R): Bile juice contains enzymes that digest fats.
Answer: C. Assertion is true, but Reason is false.
Explanation: Bile juice emulsifies fats (breaks them into small droplets), but it does not contain enzymes. It only facilitates fat digestion by lipase.
Q2.
Assertion (A): Villi in the small intestine help in absorption of nutrients.
Reason (R): Villi increase the surface area of the small intestine.
Answer: A. Both A and R are true, and R is the correct explanation.
Explanation: Villi increase surface area to enhance absorption, thus the reason correctly explains the assertion.
Q3.
Assertion (A): Hydrochloric acid in the stomach helps in digestion of proteins.
Reason (R): Hydrochloric acid activates pepsinogen into pepsin.
Answer: A. Both A and R are true, and R is the correct explanation.
Explanation: HCl activates the inactive enzyme pepsinogen into active pepsin, which digests proteins.
Q4.
Assertion (A): Saliva moistens food and helps in swallowing.
Reason (R): Saliva is alkaline and helps in protein digestion.
Answer: C. Assertion is true, but Reason is false.
Explanation: Saliva moistens food and begins carbohydrate digestion, not protein. Also, it’s slightly acidic/neutral, not alkaline.
Q5.
Assertion (A): Large intestine is the main site of absorption of nutrients.
Reason (R): The large intestine has a large surface area for absorption.
Answer: D. Assertion is false, but Reason is true.
Explanation: Small intestine is the main site of nutrient absorption. The large intestine absorbs water, not nutrients.
🧑⚖️ Case-Based Questions
Case-based questions on the topic Nutrition in Human Beings (Class 10 Science) with detailed explanations and answer options. These case-based questions test the application of knowledge and understanding of the digestive system in human beings.
Q1.
Case: A student was studying the process of digestion in the human body. During the observation of a lab experiment, he noticed that after the food was swallowed, it passed down a tube with muscular walls, which contracted and expanded, pushing the food toward the stomach. The student was curious about how this movement worked and what it was called.
Question:
What is the name of the movement that pushes food from the mouth to the stomach?
(A) Peristalsis
(B) Absorption
(C) Assimilation
(D) Ingestion
Answer: A. Peristalsis
Explanation: Peristalsis refers to the involuntary contraction and relaxation of the muscles in the walls of the alimentary canal that help push food along.
Q2.
Case:
During digestion in the stomach, the acidic environment and the action of pepsin help break down proteins. After food enters the stomach, it is churned and mixed with digestive juices for about three hours. However, the food is not fully digested here, and it moves to the next part of the digestive system for further digestion.
Question:
Which of the following substances in the stomach helps in the digestion of proteins?
(A) Hydrochloric acid
(B) Amylase
(C) Lipase
(D) Pepsin
Answer: D. Pepsin
Explanation: Pepsin is the enzyme responsible for breaking down proteins into smaller peptides in the stomach. Hydrochloric acid helps activate pepsin, but it is not the enzyme itself.
Q3.
Case:
A patient visited the doctor complaining of indigestion and stomach pain. After conducting some tests, the doctor found that the patient had an infection that reduced the mucus production in the stomach. The doctor advised the patient to take medications that would help protect the stomach lining.
Question:
What is the role of mucus in the stomach during digestion?
(A) It helps digest proteins.
(B) It neutralizes stomach acid.
(C) It protects the stomach lining from the acidic gastric juice.
(D) It emulsifies fats.
Answer: C. It protects the stomach lining from the acidic gastric juice.
Explanation: Mucus forms a protective barrier in the stomach to prevent the stomach lining from being damaged by its own acidic secretions, including hydrochloric acid.
Q4.
Case:
A teacher asked her students to observe the effects of bile in an experiment where they mixed oil with water. After adding bile, the mixture became smoother, and the fat droplets were broken into smaller pieces.
Question:
What is the role of bile in the digestion of fats?
(A) It breaks down fats into fatty acids and glycerol.
(B) It emulsifies fats, breaking them into smaller droplets for easier digestion by enzymes.
(C) It activates lipase to digest fats.
(D) It neutralizes stomach acids to aid protein digestion.
Answer: B. It emulsifies fats, breaking them into smaller droplets for easier digestion by enzymes.
Explanation: Bile, secreted by the liver, emulsifies fats (breaks them into smaller droplets), increasing the surface area for lipase to act on and break them down into fatty acids and glycerol.
Q5.
Case:
In a lab experiment, students observed that after food was digested in the small intestine, the nutrients were absorbed through the walls of the small intestine into the bloodstream. They noticed finger-like projections on the walls of the intestine that seemed to increase the surface area.
Question:
What is the name of the finger-like projections in the small intestine that help in the absorption of nutrients?
(A) Villi
(B) Microvilli
(C) Cilia
(D) Crypts
Answer: A. Villi
Explanation: Villi are tiny, finger-like projections on the inner surface of the small intestine that increase surface area for nutrient absorption. Microvilli further increase this surface area on the villi.
💡 Do You Know?
- Enamel is harder than bone.
- Small intestine is called “small” because of its narrow diameter, not its length.
- Bile juice has no enzymes but helps in fat digestion.
- Saliva is the first digestive juice food encounters.
- Herbivores have a longer small intestine than carnivores.
✅ MCQs with Answers
Q1. The enzyme present in saliva is:
A. Pepsin
B. Amylase ✅
C. Trypsin
D. Lipase
Q2. Bile is stored in:
A. Liver
B. Pancreas
C. Gall Bladder ✅
D. Stomach
Q3. Peristaltic movement occurs in:
A. Heart
B. Alimentary Canal ✅
C. Lungs
D. Kidneys
✍️ Worksheet
Fill in the blanks:
- The digestion of starch begins in the ________.
- ________ is secreted by the liver.
- The finger-like projections in the small intestine are called ________.
- The enzyme that digests fats is called ________.
- Digested food is absorbed in the ________ intestine.
Answers:
- Mouth
- Bile
- Villi
- Lipase
- Small
📝 Test Paper (10 Marks)
Q1. Define ingestion and digestion. (2 marks)
Q2. Explain the role of stomach in digestion. (2 marks)
Q3. Why is small intestine considered the site of complete digestion? (2 marks)
Q4. What are villi? What is their function? (2 marks)
Q5. What is dental caries and how can it be prevented? (2 marks)
🧠 Quick Revision Points
- Digestion begins in mouth and ends in small intestine.
- Starch → Sugar (in mouth); Proteins → Peptides (in stomach).
- Bile emulsifies fats, neutralizes stomach acid.
- Enzymes catalyze chemical digestion.
- Villi absorb nutrients; rectum stores waste.
- Dental hygiene prevents plaque and tooth decay.
