Tidal volume in a normal man at rest is
**Core Concept**
Tidal volume (TV) refers to the normal volume of air inhaled or exhaled during a single respiratory cycle, also known as a breath. It is a critical component of lung function and is essential for understanding respiratory physiology.
**Why the Correct Answer is Right**
In a normal adult at rest, the tidal volume is approximately 500 milliliters (mL). This is because the diaphragm and intercostal muscles work together to expand the lungs, increasing the volume of the thoracic cavity and allowing air to enter the lungs. The volume of air that enters the lungs during a tidal breath is determined by the pressure differences between the alveoli and the atmosphere, as well as the compliance of the lungs and chest wall.
**Why Each Wrong Option is Incorrect**
* **Option A:** This value is too low and is typically seen in patients with severe respiratory disease or in infants.
* **Option B:** This value is too high and is typically seen in patients with lung hyperinflation or in individuals performing strenuous exercise.
* **Option C:** This value is not a typical tidal volume for a normal adult at rest.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that tidal volume can be affected by various factors, including age, sex, body size, and respiratory disease. Understanding normal tidal volume values can help clinicians diagnose and manage respiratory disorders.
**Correct Answer: C. 500 mL**