Which one of the following is called inspiratory muscle in mammals?

Options

A. pleural muscle
B. external intercostal muscle
C. internal intercostal muscle
D. abdominal muscles

Answer

To solve the question "Which one of the following is called inspiratory muscle in mammals?", we can follow these steps:

### Step 1: Understand the Options
The options given are:
1. Pleural muscle
2. External intercostal muscle
3. Internal intercostal muscle
4. Abdominal muscles

### Step 2: Analyze Each Option
- **Pleural muscle**: This is not a recognized muscle involved in the process of inspiration. The pleura are membranes surrounding the lungs.
- **External intercostal muscle**: These muscles are located between the ribs and play a crucial role in the process of inhalation.
- **Internal intercostal muscle**: These muscles are also located between the ribs but are primarily involved in forced expiration, not inspiration.
- **Abdominal muscles**: These muscles are involved in forced expiration and are not considered inspiratory muscles.

### Step 3: Identify the Function of Relevant Muscles
- The **external intercostal muscles** contract during inhalation, causing the ribs to move upward and outward, which increases the volume of the thoracic cavity and decreases pressure, allowing air to flow into the lungs.

### Step 4: Conclusion
Based on the analysis, the **external intercostal muscle** is identified as the inspiratory muscle in mammals.

### Final Answer
The inspiratory muscle in mammals is the **external intercostal muscle**.

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