Exchange Of Gases

Correct Answer:

There is a negative intrapleural pressure pulling at the lung walls.

Detailed Explanation:

The lungs are located within the thoracic cavity and are surrounded by a thin, fluid-filled space called the intrapleural cavity, which lies between the two layers of the pleura — the visceral pleura (covering the lungs) and the parietal pleura (lining the thoracic wall).

Under normal conditions, the pressure in the intrapleural space is slightly negative compared to the atmospheric pressure. This negative pressure is crucial because:

• It creates a suction force that keeps the lungs expanded and closely adhered to the chest wall.
• It prevents the lungs from recoiling completely even after expiration, ensuring that the lungs don’t collapse.
• It allows a certain volume of air called the residual volume to always remain inside the lungs. This air cannot be exhaled, even with forceful breathing.
• This residual air keeps the alveoli (tiny air sacs in the lungs) open and functional for gas exchange even between breaths.

If for any reason this negative intrapleural pressure is lost — such as in the case of injury causing air to enter the pleural space (a condition called pneumothorax) — the lungs may collapse due to their natural elastic recoil.

Therefore, it is the negative intrapleural pressure that plays a key role in keeping the lungs inflated and preventing their collapse.

Asthma: An Allergic Condition

Asthma is an allergic condition in which the tissue surrounding the bronchioles of the lungs swells up and compresses the bronchioles, causing difficulty in breathing. This condition can be triggered by allergens such as pollen, dust mites, or smoke.

Key Factors Involved:

• IgE Antibodies: These are immune system proteins that play a key role in allergic reactions. They trigger the release of various chemicals that lead to inflammation and constriction of the airways in asthma.
• Histamine: A chemical released by mast cells during an allergic reaction. It contributes to inflammation and constriction of the airways.
• Serotonin: Another chemical released from mast cells, contributing to the inflammatory response and bronchoconstriction.

Conclusion:

In asthma, the combined effect of these chemicals leads to the narrowing of the airways, making it difficult to breathe and causing the characteristic symptoms such as wheezing, coughing, and shortness of breath.

The conducting part of the respiratory system is primarily responsible for transporting air to the lungs. It includes structures like the nose, pharynx, larynx, trachea, bronchi, and bronchioles. Each of these structures plays an important role in conditioning the air before it reaches the lungs. Let's analyze the functions provided in the options:

• Clears inhaled air from foreign particles: The conducting system is equipped with cilia and mucus in the airways that trap and remove foreign particles, preventing them from reaching the lungs.
• Inhaled air is humidified: As air passes through the nasal passages and upper parts of the conducting system, it is humidified, which is essential for maintaining the moisture of the alveolar surface.
• Temperature of inhaled air is brought to body temperature: The conducting airways help adjust the temperature of the inhaled air close to body temperature before it reaches the lungs.
• Provides surface for diffusion of O₂ and CO₂: This is not a function of the conducting part. The process of gas exchange, i.e., the diffusion of oxygen (O₂) and carbon dioxide (CO₂), occurs in the alveoli of the lungs, which are part of the respiratory (not the conducting) portion of the respiratory system.

Therefore, the correct answer is: Provides surface for diffusion of O₂ and CO₂, as this function is specific to the alveolar regions, not the conducting parts of the respiratory system.

In human physiology, oxygen delivery to tissues is a critical function of the circulatory system. When blood is oxygenated in the lungs, each 100 ml of this oxygen-rich blood has the capability to deliver oxygen to various tissues throughout the body.

This oxygen delivery process is primarily facilitated by hemoglobin, the protein in red blood cells that binds to oxygen. Under normal physical conditions:

• The typical arterial oxygen content is approximately 20 ml of O₂ per 100 ml of blood.
• When the blood reaches the tissues, it releases approximately 5 ml of O₂ per 100 ml of blood.

Thus, every 100 ml of oxygenated blood can deliver about 5 ml of O₂ to the tissues, aligning with the physiological characteristics of hemoglobin and the oxygen transport process.

Correct Answer: 5 ml