Problem 156 - Objective Biology for NEET

Question

Assertion: Alveoli and their duct form respiratory part of respiratory tract. Reason: This part is actual site of exchange of \(\mathrm{O}_{2}\) and \(\mathrm{CO}_{2}\) between blood and atmospheric air.

Step-by-Step Solution

Answer

Both the assertion and the reason are correct, and the reason is the correct explanation of the assertion.

Step 1: Understanding the Assertion

The assertion states: 'Alveoli and their duct form respiratory part of respiratory tract.' In the respiratory system, the alveoli and their duct are the final stages of the airway. Here the oxygen in the inhaled air is passed into the blood and carbon dioxide, a waste product of metabolism, is exhaled.

Step 2: Understanding the Reason

The reason given is: 'This part is the actual site of exchange of \(\mathrm{O}_{2}\) and \(\mathrm{CO}_{2}\) between blood and atmospheric air.' Gas exchange is the primary function of the lungs which happens in the alveoli, tiny sacs at the end of the bronchioles (airways). Here, the change between oxygen (\(\mathrm{O}_{2}\)) and carbon dioxide (\(\mathrm{CO}_{2}\)) takes place.

Step 3: Judging Assertion and Reason

The assertion 'Alveoli and their duct form respiratory part of respiratory tract' is correct, and the reason 'This part is the actual site of exchange of \(\mathrm{O}_{2}\) and \(\mathrm{CO}_{2}\) between blood and atmospheric air' is also correct and it is the correct explanation of the assertion. Therefore, both the assertion and reason are true, and the reason is the correct explanation of the assertion. So, our final judgment is: both the assertion and the reason are correct, and the reason is the correct explanation of the assertion.

Key Concepts

Respiratory Tract

The respiratory tract is an essential part of our body, functioning as the pathway for air to reach our lungs. It can be divided into upper and lower sections. The upper section includes the nose, nasal cavity, and throat, which filter, warm, and moisten the air before it travels down.
The lower section consists of the trachea, bronchi, and lungs, where the most crucial process occurs. This process takes place in the alveoli, tiny air sacs at the end of the respiratory tract. The alveoli and their ducts make up the respiratory part of the tract, meaning they are directly involved in the exchange of gases. These delicate structures serve as the transition point where air enters the bloodstream and exits after exchanging key gases.

Gas Exchange

Gas exchange is the primary function of the respiratory system. It involves swapping oxygen and carbon dioxide between the lungs and blood cells. Without this process, our cells wouldn't get the oxygen needed for energy, nor would they be able to rid themselves of carbon dioxide produced as a waste product.
This vital exchange happens in the lungs' alveoli. These tiny sacs are perfectly designed for this task, with thin walls that allow gases to pass through easily. Oxygen from inhaled air enters the blood through alveolar walls, while carbon dioxide from the blood passes in the opposite direction to be exhaled. This efficient exchange is crucial for maintaining life-sustaining breathing and energy production in our bodies.

Oxygen Exchange

Oxygen exchange is a critical step in the process of breathing. When we breathe in, air travels through the respiratory tract and fills the alveoli. Here, oxygen passes through the thin walls of the alveoli and enters the surrounding capillaries.
Capillaries are small blood vessels that weave around each alveolus, allowing oxygen to dissolve into the blood. This oxygen-rich blood is then transported throughout the body, providing energy to all cells and tissues. Without this exchange, our cells wouldn't have the necessary oxygen to perform essential functions, highlighting its importance in sustaining life.

Carbon Dioxide Exchange

Just as oxygen is taken in, carbon dioxide, a metabolic waste product, must be removed effectively. During carbon dioxide exchange, carbon dioxide diffuses from the bloodstream back into the alveoli.
As blood circulates to the lungs, it carries carbon dioxide from body tissues. This waste gas moves from the blood, where it is at higher concentrations, to the alveoli, where it can be expelled from the body through exhalation. Efficient removal of carbon dioxide is equally as important as oxygen intake, as it prevents the buildup of acid in the blood, maintaining a healthy pH balance.