Volume of thoracic chamber increases in antero-
prosterior and dorse-ventral axis in rabbit by

Options

A. Contraction of diaphragm and external intercostal muscles respectively
B. Relaxation of diaphragm and external intercostal muscles respectively
C. Relaxation of diaphragm and abdominal muscles respectively
D. Contraction of abdominal muscles and relaxation of external infercostal muscles
respectively

Answer

To answer the question regarding how the volume of the thoracic chamber increases in the anteroposterior and dorsoventral axes in rabbits, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding the Anatomy**:
- The rabbit, being a mammal, has a respiratory system that includes lungs located in the thoracic cavity. The thoracic cavity is the space within the chest that houses the lungs and is bounded by the ribs, diaphragm, and sternum.

2. **Role of the Diaphragm**:
- The diaphragm is a dome-shaped muscle located below the lungs. It plays a crucial role in respiration. When the diaphragm contracts, it flattens and moves downward, which increases the volume of the thoracic cavity in the anteroposterior axis (front to back).

3. **Action of External Intercostal Muscles**:
- The external intercostal muscles are located between the ribs. When these muscles contract, they lift the ribs and sternum upward and outward. This action increases the volume of the thoracic cavity in the dorsoventral axis (top to bottom).

4. **Resulting Increase in Volume**:
- The combined actions of the diaphragm contracting and the external intercostal muscles contracting lead to an overall increase in the volume of the thoracic chamber, allowing for air to be drawn into the lungs during the process of inhalation.

5. **Conclusion**:
- Therefore, the volume of the thoracic chamber in rabbits increases due to the contraction of the diaphragm and the external intercostal muscles, which respectively increase the volume in the anteroposterior and dorsoventral axes.

### Final Answer:
The volume of the thoracic chamber increases in the anteroposterior and dorsoventral axes in rabbits due to the contraction of the diaphragm and external intercostal muscles.

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