Problem 120 - Objective Biology for NEET

Question

The volume of air that remains in the lungs after normal expiration is (a) Residual volume (b) Vital capacity (c) Expiratory capacity (d) Functional residual capacity

Step-by-Step Solution

Answer

The volume of air that remains in the lungs after normal expiration is (d) Functional Residual Capacity.

Step 1: Define Residual Volume

Residual Volume (RV) is the amount of air that remains in the lungs after a maximal exhalation, preventing the lungs from collapsing.

Step 2: Define Vital Capacity

Vital Capacity (VC) is the total amount of air that can be exhaled after a maximum inhalation. This is not what we're looking for either, because it involves maximal inhalation and exhalation, not normal expiration.

Step 3: Define Expiratory Capacity

Expiratory Capacity (EC) is the total volume of air that can be exhaled after normal inhalation. This isn't what we're looking for as it involves expelling air after a normal inhalation, not what remains in the lungs after a normal exhalation.

Step 4: Define Functional Residual Capacity

Functional Residual Capacity (FRC) is the volume of air remaining in the lungs after a normal, passive exhalation. This perfectly matches the definition we're seeking.

Key Concepts

Respiratory Volumes

Respiratory volumes are essential components in understanding how our lungs work and help us breathe effectively. They describe the different quantities of air associated with different phases of the respiratory cycle.
Essential respiratory volumes include:

• Tidal Volume (TV): The air inhaled or exhaled during a normal breath.
• Inspiratory Reserve Volume (IRV): The extra air that can be inhaled with a deep breath beyond the normal tidal inhalation.
• Expiratory Reserve Volume (ERV): The additional air that can be forcefully exhaled after the end of a normal tidal exhalation.
• Residual Volume (RV): The air left in the lungs after a forceful exhalation, preventing lung collapse.

By understanding these components, we can assess lung function in different circumstances, whether at rest or during intense activity.

Residual Volume

Residual Volume (RV) is a crucial lung capacity metric indicating the amount of air remaining in the lungs after maximum exhalation.
This volume is critical for several reasons:

• Prevents lung collapse by maintaining constant pressure within the lung tissues.
• Ensures continuous gas exchange occurs even between breaths.
• Provides a reserve for instances when more oxygen is required by the body, such as during exercise.

Understanding RV is vital for diagnosing and managing respiratory conditions like chronic obstructive pulmonary disease (COPD) where this volume can be affected.

Vital Capacity

Vital Capacity (VC) is an important measure reflecting the total amount of air a person can voluntarily exchange during the respiratory cycle.
This capacity includes:

• Tidal Volume (TV)
• Inspiratory Reserve Volume (IRV)
• Expiratory Reserve Volume (ERV)

To calculate VC, you sum TV, IRV, and ERV. It represents the maximum volume of air expelled from the lungs after a maximum inhalation.
Knowing one's VC can be indicative of physical abilities or limitations, informing health decisions and fitness levels.

Expiratory Capacity

Expiratory Capacity (EC) focuses on the total volume of air that can be expelled from the lungs after a normal inhalation. It combines two important components:

• Tidal Volume (TV): Air moved into or out of the lungs during normal breathing.
• Expiratory Reserve Volume (ERV): Extra air that can be exhaled forcefully beyond a normal exhalation.

This capacity helps in understanding the extent of reserve capacity available in the lungs for exhaling more air forcefully, which can be crucial during physical exertion.
By analyzing EC, medical professionals can determine if a person has normal respiratory patterns or if there are potential limitations or conditions affecting lung function.