Human Body Systems - Grade 9 Natural Science Notes
1. Respiratory System
Functions:
1. Brings oxygen into the body.
2. Removes carbon dioxide (a waste gas).
3. Helps produce speech (vocal cords use air).
Main Structures: Nose, trachea, bronchi, lungs, alveoli.
Process: Air enters the lungs via the nose or mouth. Oxygen moves into alveoli and diffuses into blood, while carbon
dioxide exits.
Health Issues:
- Asthma: Airways become inflamed and narrow, making it hard to breathe.
- Bronchitis: Infection causes swelling and mucus in the bronchi.
- Pneumonia: Alveoli fill with fluid due to infection, reducing oxygen intake.
2. Circulatory System
Functions:
1. Delivers oxygen and nutrients to body cells.
2. Removes waste like carbon dioxide.
3. Helps defend the body with white blood cells.
Main Structures: Heart, blood, arteries, veins, capillaries.
Process: Heart pumps oxygen-rich blood. Capillaries exchange gases and nutrients. Veins return blood to the heart.
Health Issues:
- Hypertension: High blood pressure damages vessels.
- Heart Attack: Blockage in heart arteries causes tissue death.
- Stroke: Brain cells die due to blocked or burst blood vessel.
3. Digestive System
Functions:
1. Breaks down food.
2. Absorbs nutrients.
3. Removes waste.
Main Structures: Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.
Process: Food is digested mechanically and chemically. Nutrients are absorbed in the small intestine. Waste exits
through the anus.
Health Issues:
- Constipation: Difficulty passing stool.
- Ulcers: Sores in stomach lining.
- Diarrhea: Frequent, watery stools due to infections or food issues.
1. Respiratory System
Functions:
1. Brings oxygen into the body.
2. Removes carbon dioxide (a waste gas).
3. Helps produce speech (vocal cords use air).
Main Structures: Nose, trachea, bronchi, lungs, alveoli.
Process: Air enters the lungs via the nose or mouth. Oxygen moves into alveoli and diffuses into blood, while carbon
dioxide exits.
Health Issues:
- Asthma: Airways become inflamed and narrow, making it hard to breathe.
- Bronchitis: Infection causes swelling and mucus in the bronchi.
- Pneumonia: Alveoli fill with fluid due to infection, reducing oxygen intake.
2. Circulatory System
Functions:
1. Delivers oxygen and nutrients to body cells.
2. Removes waste like carbon dioxide.
3. Helps defend the body with white blood cells.
Main Structures: Heart, blood, arteries, veins, capillaries.
Process: Heart pumps oxygen-rich blood. Capillaries exchange gases and nutrients. Veins return blood to the heart.
Health Issues:
- Hypertension: High blood pressure damages vessels.
- Heart Attack: Blockage in heart arteries causes tissue death.
- Stroke: Brain cells die due to blocked or burst blood vessel.
3. Digestive System
Functions:
1. Breaks down food.
2. Absorbs nutrients.
3. Removes waste.
Main Structures: Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.
Process: Food is digested mechanically and chemically. Nutrients are absorbed in the small intestine. Waste exits
through the anus.
Health Issues:
- Constipation: Difficulty passing stool.
- Ulcers: Sores in stomach lining.
- Diarrhea: Frequent, watery stools due to infections or food issues.
