The structrue which does not contribute to the breathing movements in mamals s

Options

A. rib
B. larynx
C. diaphragm
D. intercoastal muscles

Answer

To solve the question regarding which structure does not contribute to the breathing movements in mammals, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Breathing Process**: Breathing in mammals consists of two main phases: inhalation (inspiration) and exhalation (expiration).

2. **Identify Structures Involved in Breathing**: The primary structures that contribute to the breathing movements include:
- **Diaphragm**: A dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. It contracts and relaxes to facilitate breathing.
- **Ribs**: The rib cage expands and contracts during breathing, helping to change the volume of the thoracic cavity.
- **Intercostal Muscles**: These muscles are located between the ribs and assist in expanding and contracting the rib cage during inhalation and exhalation.

3. **Examine the Options**:
- **Rib**: Contributes to breathing movements.
- **Larynx**: While it is part of the respiratory system, it primarily functions as a passage for air and does not actively contribute to the mechanics of breathing.
- **Diaphragm**: Contributes to breathing movements.
- **Intercostal Muscles**: Contribute to breathing movements.

4. **Determine the Correct Answer**: Since the larynx does not play a role in the physical act of inhalation or exhalation, it is the structure that does not contribute to breathing movements in mammals.

### Conclusion:
The correct answer is **Larynx** (Option B), as it does not contribute to the breathing movements.

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