Movement of air into and out of the lungs is carried out by a creating____ between the lungs and atmosphere.

Answer

To solve the question, "Movement of air into and out of the lungs is carried out by creating ____ between the lungs and atmosphere," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Breathing**: Breathing involves the movement of air between the atmosphere and the lungs. This process is essential for gas exchange, allowing oxygen to enter the body and carbon dioxide to be expelled.

2. **Role of Pressure**: The movement of air is primarily driven by differences in air pressure. When the pressure inside the lungs is different from the atmospheric pressure, air will flow in or out of the lungs.

3. **Creating a Pressure Gradient**: The key to moving air in and out of the lungs is creating a pressure gradient. This means that the pressure inside the lungs must be lower than the atmospheric pressure for air to flow in (inhalation) and higher for air to flow out (exhalation).

4. **Muscle Involvement**: The diaphragm and intercostal muscles play a crucial role in changing the volume of the thoracic cavity, which in turn alters the pressure in the lungs. When the diaphragm contracts, it flattens, increasing the volume of the thoracic cavity and decreasing the pressure in the lungs, allowing air to flow in.

5. **Conclusion**: Therefore, the blank in the question can be filled with "pressure gradient." The correct answer is "pressure gradient."

### Final Answer:
Movement of air into and out of the lungs is carried out by creating **pressure gradient** between the lungs and atmosphere.