Explain the mechanism of breathing with neat labelled sketches.

Explanation

### Step-by-Step Solution

**Step 1: Understanding Breathing Mechanism**
Breathing involves two main processes: **inspiration** (inhalation) and **expiration** (exhalation). During inspiration, atmospheric air is drawn into the lungs, while during expiration, air is expelled from the lungs.

**Step 2: Role of Pressure Gradient**
The movement of air into and out of the lungs is facilitated by creating a pressure gradient. This gradient is established by the diaphragm and intercostal muscles, which control the volume of the thoracic cavity.

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