True statement regarding difference between apex and base of lung, in erect posture is:March 2012, March 2013
**Core Concept**
In an erect posture, the lungs have a vertically oriented structure, with the apices being the most superior parts and the bases being the most inferior parts. This orientation affects the distribution of blood flow and ventilation within the lungs.
**Why the Correct Answer is Right**
The correct answer is related to the difference in blood flow and ventilation between the apex and base of the lung. The apex of the lung receives less blood flow and ventilation due to its higher elevation, resulting in a lower partial pressure of oxygen (pO2) and a higher partial pressure of carbon dioxide (pCO2). In contrast, the base of the lung receives more blood flow and ventilation, resulting in a higher pO2 and lower pCO2. This gradient is due to the effects of gravity on blood flow and ventilation, as well as the differences in lung compliance and airway resistance between the apex and base.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct difference between the apex and base of the lung. While it may be related to the topic, it is not a clear or accurate statement.
**Option B:** This option is incorrect because it does not accurately describe the differences in blood flow and ventilation between the apex and base of the lung. The apex of the lung actually receives less blood flow and ventilation, not more.
**Option C:** This option is incorrect because it does not specify the correct difference between the apex and base of the lung. While it may be related to the topic, it is not a clear or accurate statement.
**Option D:** This option is incorrect because it does not accurately describe the differences in blood flow and ventilation between the apex and base of the lung.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the apex of the lung is more prone to atelectasis and hypoxia due to its higher elevation and lower blood flow and ventilation. This can be particularly relevant in clinical situations where patients are at risk for respiratory compromise, such as during anesthesia or in patients with chronic lung disease.
**Correct Answer: B. The apex receives less blood flow and ventilation than the base of the lung.**