Considering the following labels for mentioned structured and select the correct sequence of their arrangement `:-`
`A=` Terminal bronhiole
`B=` Respiratory bronchiole
`C=` Tertiary bronchi
`D=` Primary bronchi
`E=` Secondary bronchi
`F=` Total pulmonary bronchioles

Options

A. `D rarr E rarr C rarr A rarr F rarr B `
B. `A rarr B rarr D rarr E rarr C rarr F`
C. `C rarr F rarr A rarr B rarr D rarr E`
D. `D rarr E rarr F rarr C rarr B rarr A`

Answer

To determine the correct sequence of the respiratory structures, we need to understand the arrangement of the bronchi and bronchioles in the respiratory system. Here’s the step-by-step solution:

### Step-by-Step Solution:

1. **Starting Point - Primary Bronchi (D)**: The respiratory pathway begins with the primary bronchi, which branch off from the trachea. This is the first structure in the sequence.

2. **Next - Secondary Bronchi (E)**: After the primary bronchi, the next structures are the secondary bronchi. Each primary bronchus divides into secondary bronchi that lead to the lobes of the lungs.

3. **Following - Tertiary Bronchi (C)**: The secondary bronchi further divide into tertiary bronchi. These bronchi supply the segments of the lungs.

4. **Then - Terminal Bronchioles (A)**: After the tertiary bronchi, the pathway continues to the terminal bronchioles. These are the last branches of the conducting zone before the respiratory zone begins.

5. **Next - Total Pulmonary Bronchioles (F)**: The terminal bronchioles lead into the total pulmonary bronchioles, which include all the smaller bronchioles in the lungs.

6. **Finally - Respiratory Bronchioles (B)**: The last structure in this sequence is the respiratory bronchioles, which are involved in gas exchange and lead to the alveoli.

### Correct Sequence:
The correct sequence of arrangement is:
- D (Primary bronchi)
- E (Secondary bronchi)
- C (Tertiary bronchi)
- A (Terminal bronchioles)
- F (Total pulmonary bronchioles)
- B (Respiratory bronchioles)

### Final Answer:
The correct sequence is: **D, E, C, A, F, B**

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