Class 12 Biology - Human Respiratory System

Aim

To study the structure and function of the human respiratory system and demonstrate the mechanism of breathing.

Materials Required

• 3D model or diagram of the human respiratory system
• Balloon
• Plastic bottle (empty)
• Rubber sheet or glove
• Scissors

Image Reference

Procedure

1. Study the Respiratory System:
   • Observe a model or diagram of the human respiratory system.
   • Identify the trachea, bronchi, lungs, alveoli, and diaphragm.
2. Demonstrate Breathing Movements:
   • Cut the bottom of a plastic bottle to create an open base.
   • Insert a balloon into the neck of the bottle, ensuring it is secured tightly with a rubber band.
   • Cover the open base of the bottle with a rubber sheet or glove to act as the diaphragm. Fix it tightly using a rubber band.
   • Pull the rubber sheet downwards gently to simulate inhalation. The balloon inside will expand, showing the lungs filling with air.
   • Push the rubber sheet upwards gently to simulate exhalation. The balloon will deflate, showing the lungs expelling air.

Observation

During the experiment, the following observations are made:

• When the rubber sheet (diaphragm) is pulled down, the balloon (lungs) expands as air enters, simulating inhalation.
• When the rubber sheet is pushed up, the balloon deflates as air is expelled, simulating exhalation.
• This demonstrates the role of the diaphragm in breathing by creating a pressure gradient for air movement in and out of the lungs.

Inference

The respiratory system enables gas exchange, where oxygen is inhaled into the lungs and carbon dioxide is exhaled. The diaphragm and intercostal muscles play a crucial role in creating pressure changes that facilitate breathing.

Precautions

• Ensure the balloon is securely attached to prevent air leakage.
• Handle the rubber sheet gently to avoid tearing it.
• Observe the model or diagram carefully to understand the arrangement of the respiratory organs.

Video Reference