Anatomical dead space of normal lung is
**Core Concept**
Anatomical dead space of the lung refers to the volume of air that remains in the conducting airways (trachea, bronchi, bronchioles) and does not participate in gas exchange. This concept is essential in understanding the mechanics of breathing and the efficiency of gas exchange in the lungs.
**Why the Correct Answer is Right**
The anatomical dead space of the normal lung is approximately 150 mL. This is because the conducting airways, which are responsible for conducting air to the alveoli, do not participate in gas exchange. The air in these airways is not in contact with the capillary blood, which is necessary for gas exchange to occur. The anatomical dead space is a significant portion of the total lung volume and can affect the efficiency of breathing, especially during exercise or in conditions where lung function is compromised.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately reflect the anatomical dead space of the normal lung.
**Option B:** This option is incorrect because it is too high and not supported by scientific evidence.
**Option C:** This option is incorrect because it is too low and does not account for the volume of the conducting airways.
**Clinical Pearl / High-Yield Fact**
Remember that the anatomical dead space can be affected by conditions such as chronic obstructive pulmonary disease (COPD), which can lead to an increase in anatomical dead space and a decrease in lung function.
**Correct Answer: C. 150 mL.**