Problem 157 - Objective Biology for NEET

Question

Assertion: External nostril to terminal bronchioles constitutes conducting as well as respiratory part of respiratory tract. Reason: It help in conduction of atmospheric air to the alveoli as well as diffusion of \(\mathrm{O}_{2}\) and \(\mathrm{CO}_{2}\) between blood and atmospheric air.

Step-by-Step Solution

Answer

The assertion is partially accurate. While the path from the external nostril to the terminal bronchioles does perform the function of conducting air, it's only from the bronchioles onwards that gas exchange begins, which is the respiratory function. The reason is true, but it doesn't fully support the assertion as it omits this detail.

Step 1: Identify the Components of the Respiratory Tract

The respiratory tract is made up of the nose or nostrils, the pharynx, the larynx, the trachea, the bronchi, the bronchioles, and the alveoli. This path serves the function of delivering atmospheric air to the alveoli, which is the site of gas exchange in the lungs.

Step 2: Understand the Conduction and Respiratory Parts

The conduction part of the respiratory tract involves structures that transport incoming air from the external environment to the lungs. These are cold, sterile, hairs-lined parts such as the nose, pharynx, larynx, trachea, and larger bronchi. The respiratory part involves structures where the actual gas exchange occurs (bronchioles, alveolar ducts, alveoli). It’s thin, moist, has huge surface area and blood supply.

Step 3: Analysis and Confirmation

Given the functions of the conducting and respiratory parts, it's clear that the terminal bronchioles are part of the conducting and respiratory tract because they not only transport air but are also the site where gas exchange starts to occur. The external nostril, however, only conducts air and does not participate in gas exchange. The reason is accurate, but it doesn't wholly support the assertion, as the gas exchange function starts at bronchioles, not from nostrils.

Key Concepts

Conduction Part

The conduction part of the respiratory system acts like a series of tunnels, carefully transporting air from the outside world into the depths of the lungs. This journey begins at the nostrils, where air first enters, passing through the nasal cavity. The key components of the conduction system include the nose, pharynx, larynx, trachea, and the major bronchi.

• Nose: Air is first inhaled through the nostrils, which help filter, warm, and moisten it.
• Pharynx: It's the next path for air, shared with the digestive system but expertly routed to the windpipe via the epiglottis.
• Larynx: Often referred to as the voice box, this organ plays a crucial role in speech and continues air conduction.
• Trachea and Bronchi: These serve as highways, successfully dividing into smaller paths to lead air into each lung.

The conduction part ensures the air is conditioned and sterile before it reaches deeper lung regions. It doesn't involve oxygen transfer to the bloodstream, but it is essential for air delivery to the respiratory zone.

Respiratory Part

Located deeper within the lung tissue, the respiratory part of the respiratory system is where the magic of gas exchange truly begins. This part includes smaller bronchioles, alveolar ducts, and mainly, the alveoli—tiny air sacs with thin walls, facilitating as the primary sites for gas exchange.

• Bronchioles: The smallest branches of the bronchi that carry air closer to the respiratory surfaces.
• Alveolar Ducts: These connect the bronchioles to the alveolar sacs, funneling air to these critical locations.
• Alveoli: Air-filled sacs where oxygen diffuses into the blood and carbon dioxide is expelled out.

The respiratory part possesses a vast surface area and a rich supply of blood vessels, enhancing its efficiency. Its moist and thin-walled structure is perfectly designed to maximize the exchange of gases between the air and blood, ensuring that life's essential processes can continue.

Gas Exchange

The process of gas exchange in the respiratory system happens primarily in the alveoli, tiny sacs within the lungs. Each lung holds millions of alveoli, providing a massive surface for oxygen and carbon dioxide to swap places.

The Mechanism of Gas Exchange

Within each alveolus, oxygen from inhaled air passes through a thin membrane into the bloodstream. The same membrane leads carbon dioxide—waste product from cells—to travel from the blood into the alveolus to be exhaled.

• Oxygen Transport: Once in the bloodstream, oxygen binds to hemoglobin molecules in red blood cells.
• Carbon Dioxide Removal: This waste gas is carried in the blood and released into the alveoli when the blood reaches the lungs.

The gas exchange process is driven by concentration gradients; oxygen flows from high oxygen areas to low, and similarly, carbon dioxide moves from where it's concentrated to less concentrated zones. This dynamic and efficient system ensures that your body's tissues continually receive fresh oxygen supply and are freed from carbon dioxide buildup.