CBSE CLASS 10 SCIENCE LIFE PROCESSES — DIGESTION IN HUMAN BEINGS

🧬 CBSE CLASS 10 SCIENCE

LIFE PROCESSES — DIGESTION IN HUMAN BEINGS

Core Idea:
Food provides energy and materials needed for growth, repair and maintenance. Before our cells can use food, complex food substances must be broken down into simpler, soluble substances. This process is called digestion.

1. 🍎 WHAT IS NUTRITION?

Nutrition is the process by which organisms obtain and utilise food for energy, growth, repair and maintenance.

In human beings, nutrition is holozoic, meaning food is taken into the body and then internally digested.

The major steps are:

Ingestion → Digestion → Absorption → Assimilation → Egestion

2. THE HUMAN DIGESTIVE SYSTEM

The human digestive system consists mainly of:

Alimentary canal

Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Rectum → Anus..

Associated digestive glands

• Salivary glands

• Liver

• Pancreas

3. DIGESTION IN THE MOUTH

Digestion begins in the mouth.

Food is:

• mechanically broken down by chewing

• mixed with saliva

• converted into a soft mass called a bolus

Saliva contains the enzyme salivary amylase.

Starch → Simpler sugars

Thus, the digestion of carbohydrates begins in the mouth.

Chewing increases the surface area of food available for enzyme action.

4.  OESOPHAGUS

The swallowed food moves from the mouth to the stomach through the oesophagus.

Food is pushed forward by rhythmic muscular contractions called peristalsis.

⭐ Remember:

Peristalsis = wave-like muscular movement that pushes food through the alimentary canal.

5. DIGESTION IN THE STOMACH

The stomach is a muscular, sac-like organ.

Its inner lining contains gastric glands.

These glands release:

① Hydrochloric acid (HCl)

• Makes the stomach contents acidic.

• Provides the acidic medium required for the action of pepsin.

• Helps create conditions unsuitable for many harmful microbes.

② Pepsin

• Begins the digestion of proteins.

Proteins → Simpler substances

③ Mucus

• Protects the inner lining of the stomach from the acidic gastric juice.

⭐ Important connection

HCl → acidic medium → pepsin works effectively → protein digestion

6. 🧪 ROLE OF THE LIVER AND BILE

The liver is the largest gland of the human body.

It produces bile, which is stored in the gall bladder.

Bile is released into the small intestine.

Functions of bile:

1. Neutralises the acidic food coming from the stomach.

2. Emulsifies fats.

What is emulsification?

Large fat globules are broken into tiny droplets, increasing the surface area available for the action of lipase.

Bile does NOT digest fat directly.
It helps in the digestion of fats by emulsification.

7.  ROLE OF THE PANCREAS

The pancreas releases pancreatic juice into the small intestine.

It contains enzymes such as:

Pancreatic amylase- Acts on carbohydrates.

Trypsin- Acts on proteins.

Lipase- Acts on fats.

8. 🌟 SMALL INTESTINE — THE MAIN SITE OF DIGESTION AND ABSORPTION

The small intestine is the major site where digestion of food is completed.

Digestive juices from liver, pancreas and intestinal glands act here.

Final products of digestion:

9. 🫧 VILLI — THE ABSORPTION SPECIALISTS

The inner lining of the small intestine contains numerous tiny finger-like projections called villi.

Villi increase the surface area for absorption.

Each villus has:

• a thin wall

• a rich network of blood capillaries

• a lymph vessel/lacteal

Why are villi important?

They allow digested nutrients to be absorbed efficiently into the body.

⭐ Exam Alert- If asked “How is the small intestine adapted for absorption?”

Mention:

1. It is long and highly coiled.

2. Its inner surface has numerous villi.

3. Villi provide a large surface area.

4. Villi have thin walls.

5. They possess a rich blood supply.

10.  ABSORPTION vs ASSIMILATION

These terms are frequently confused.

Absorption- Digested food passes from the intestine into the blood/lymph.

Assimilation- The absorbed nutrients are taken up and used by body cells.

Easy distinction:

Absorption = enters the body fluids

Assimilation = used by cells

11.  LARGE INTESTINE

The remaining material passes into the large intestine.

Its major functions include:

• absorption of water

• absorption of some salts

• formation and storage of faeces

The undigested material is eventually expelled through the anus.

This removal is called egestion.

🧩 COMPLETE DIGESTION MAP

                 FOOD
                   ↓
                MOUTH
       Saliva + chewing
                   ↓
             Carbohydrate
              digestion
                   ↓
             OESOPHAGUS
             Peristalsis
                   ↓
               STOMACH
        HCl + Pepsin + Mucus
                   ↓
             Protein digestion
                   ↓
          ┌─────────────────┐
          │ SMALL INTESTINE │
          └─────────────────┘
             ↑           ↑
           Bile       Pancreatic
                     juice
             ↓           ↓
          Emulsification + 
          digestion by enzymes
                   ↓
       Complete digestion of food
                   ↓
                 VILLI
                   ↓
               ABSORPTION
                   ↓
              ASSIMILATION
                   ↓
          LARGE INTESTINE
            Water absorbed
                   ↓
                RECTUM
                   ↓
                 ANUS
                   ↓
                EGESTION

🧠 ENZYME SHEET

🎯 HIGH-YIELD CONCEPTS: Remember these six connections:

1. Salivary amylase → starch

2. HCl → acidic medium for pepsin

3. Pepsin → protein digestion

4. Bile → emulsification of fats

5. Pancreatic enzymes → digestion of carbohydrates, proteins and fats

6. Villi → absorption of digested food

🔥 10 HIGH-FREQUENCY CBSE PYQ THEMES — DIGESTION

1. What is the role of hydrochloric acid in the stomach? Why is it necessary for digestion?

2. What is the role of the pancreas in digestion? Name the important enzymes present in pancreatic juice.

3. Explain the role of bile in the digestion of fats.

4. How is the small intestine adapted for efficient absorption of digested food

5. Describe how carbohydrates, proteins and fats are digested in the human digestive system.

6. What are the functions of the secretions of gastric glands? 

7. Explain the role of the mouth in the digestion of food.

8. Draw a neat labelled diagram of the human alimentary canal. Label the mouth, oesophagus, stomach and intestine.

9. A student is given a situation involving digestion and is asked to identify the enzyme, organ or process responsible. Explain the reasoning.