Human Digestive System – CHEMASH Biology
The Human Digestive System is responsible for breaking down food into simple substances that can be absorbed and used by the body. This chapter is extremely important for Class 10, 11, 12 Boards & NEET 2026.
Related Topics: Biomolecules | Enzymes & Metabolism | Respiration in Plants
Table of Contents
- Overview
- Organs of Digestive System
- Digestive Enzymes
- Process of Digestion
- Absorption of Nutrients
- Common Disorders
- MCQs
- FAQs
Overview
Digestion is the mechanical and chemical breakdown of complex food into simple soluble molecules.
Organs of Human Digestive System
- Mouth: Ingestion & chewing
- Esophagus: Transports food
- Stomach: Protein digestion begins
- Small Intestine: Major digestion & absorption
- Large Intestine: Water absorption
- Liver: Produces bile
- Pancreas: Secretes digestive enzymes
Digestive Enzymes
| Enzyme | Secreted By | Acts On |
|---|---|---|
| Salivary Amylase | Salivary Glands | Starch |
| Pepsin | Stomach | Proteins |
| Trypsin | Pancreas | Proteins |
| Lipase | Pancreas | Fats |
Process of Digestion (Flow)
Mouth → Esophagus → Stomach → Small Intestine → Large Intestine → Rectum
- Mechanical digestion starts in mouth.
- Chemical digestion begins with saliva.
- Stomach uses HCl & pepsin.
- Small intestine completes digestion.
Absorption of Nutrients
Occurs mainly in small intestine through villi.
- Glucose → Blood
- Amino acids → Blood
- Fatty acids → Lymph
Common Digestive Disorders
- Acidity
- Ulcer
- Diarrhea
- Constipation
1️⃣ Acidity (Hyperacidity)
Acidity occurs when the stomach produces excess hydrochloric acid (HCl). This leads to a burning sensation in the chest known as heartburn.
Causes:
- Spicy and oily food
- Skipping meals
- Stress
- Excess tea/coffee
Symptoms:
- Burning sensation in chest
- Sour taste in mouth
- Nausea
Prevention:
- Eat balanced meals
- Avoid junk food
- Reduce stress
2️⃣ Peptic Ulcer
An ulcer is a wound or sore in the lining of the stomach or small intestine. It is often caused by infection of Helicobacter pylori bacteria.
Causes:
- H. pylori infection
- Excess acid production
- Long-term painkiller use
Symptoms:
- Severe stomach pain
- Vomiting
- Loss of appetite
Important for NEET:
Ulcers occur due to damage of protective mucus layer in stomach.
3️⃣ Diarrhea
Diarrhea is a condition in which a person passes watery stools frequently. It leads to loss of water and salts (dehydration).
Causes:
- Bacterial or viral infection
- Contaminated food/water
- Food poisoning
Symptoms:
- Loose motion
- Weakness
- Dehydration
Prevention:
- Drink clean water
- Maintain hygiene
- ORS solution during dehydration
4️⃣ Constipation
Constipation is difficulty in passing stool due to slow bowel movement. It is very common in students due to poor diet habits.
Causes:
- Low fiber diet
- Less water intake
- Lack of exercise
Symptoms:
- Hard stool
- Abdominal pain
- Bloating
Prevention:
- Eat fiber-rich food
- Drink enough water
- Regular physical activity
MCQs with Explanation (NEET 2026)
1. Protein digestion starts in:
Answer: Stomach
Explanation: Pepsin breaks proteins.
2. Maximum absorption occurs in:
Answer: Small intestine
3. Bile is produced by:
Answer: Liver
4. Lipase acts on:
Answer: Fats
FAQs
Q1. What is the function of bile?
A: It emulsifies fats.
Q2. Where does digestion complete?
A: Small intestine.
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