Read the following statements
(i) the point of bifurcation of trachea is called carina and is at the level of 5th thoracic vertebra
(ii)the right bronchus is shorter wider and more in line with trachea than the left bronchus
(iii) the bronchioles are without cartilaginous rings
(iv) the surfactant of lungs is secreted in infants between 6th and 7th month of life
which of these are correct ?

Options

A. I,ii & iii
B. ii , iii & iv
C. I, iii & iv
D. all are correct

Answer

To determine which statements about the respiratory system are correct, let's analyze each statement step by step.

### Step 1: Analyze Statement (i)
**Statement:** The point of bifurcation of the trachea is called carina and is at the level of the 5th thoracic vertebra.

**Analysis:**
- The trachea does bifurcate into the right and left bronchi at a point known as the carina.
- This bifurcation occurs at the level of the 5th thoracic vertebra (T5).

**Conclusion:** This statement is **correct**.

### Step 2: Analyze Statement (ii)
**Statement:** The right bronchus is shorter, wider, and more in line with the trachea than the left bronchus.

**Analysis:**
- The right bronchus is indeed shorter and wider compared to the left bronchus.
- It is also more vertically aligned with the trachea, making it a more direct pathway for inhaled objects.

**Conclusion:** This statement is **correct**.

### Step 3: Analyze Statement (iii)
**Statement:** The bronchioles are without cartilaginous rings.

**Analysis:**
- The primary bronchi have C-shaped cartilaginous rings that help maintain their structure.
- However, bronchioles (especially the smaller ones) do not have cartilaginous rings; they are primarily composed of smooth muscle and elastic fibers.

**Conclusion:** This statement is **correct**.

### Step 4: Analyze Statement (iv)
**Statement:** The surfactant of the lungs is secreted in infants between the 6th and 7th month of life.

**Analysis:**
- Surfactant, specifically lecithin, is secreted by type II alveolar cells (pneumocytes) during the late stages of fetal development, specifically between 24 to 28 weeks of gestation (which corresponds to the 6th to 7th month of pregnancy).
- The statement is misleading because it implies secretion occurs after birth rather than during gestation.

**Conclusion:** This statement is **incorrect**.

### Final Conclusion
The correct statements are (i), (ii), and (iii). Therefore, the correct answer is that statements 1, 2, and 3 are correct.