A number of very thin , irregular - walled and vascularised bag - like structures are called as

Options

A. Cardiac notches
B. Alveoli
C. Nephron
D. Neurons

Answer

To solve the question, we need to identify which of the given options refers to "very thin, irregular-walled and vascularized bag-like structures."

### Step-by-Step Solution:

1. **Understanding the Question**: The question describes structures that are thin, irregular-walled, vascularized, and bag-like. We need to analyze each option to find the best fit.

2. **Analyzing the Options**:
- **Cardiac Notches**: These are indentations in the heart and do not fit the description of bag-like structures.
- **Alveoli**: These are tiny air sacs in the lungs that are indeed thin-walled, vascularized, and bag-like. They are crucial for gas exchange in the respiratory system.
- **Nephron**: This is the functional unit of the kidney, involved in filtering blood and forming urine, but it does not fit the description of bag-like structures.
- **Neuron**: This is a nerve cell that transmits signals in the nervous system, not a bag-like structure.
- **Neural System**: This refers to the entire network of neurons and does not describe a specific structure.

3. **Identifying the Correct Answer**: Based on the analysis, the only option that matches the description of "very thin, irregular-walled and vascularized bag-like structures" is **Alveoli**.

4. **Conclusion**: Therefore, the correct answer is **Alveoli**.

### Final Answer:
**Alveoli**

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