Anatomy and Physiology I (BIO 2010)

Correct Answer C. Smaller alveoli will require significantly higher pressure to stay open, leading to potential collapse.

Explanation

LaPlace's law states that the pressure required to keep an alveolus open is inversely proportional to its radius. Without surfactant, smaller alveoli require greater pressure to stay open, making them more prone to collapse. This contributes to the development of neonatal respiratory distress syndrome (NRDS) and other conditions where surfactant is deficient.

Why Other Options Are Wrong

A. Alveoli will collapse easily due to lower pressure requirements.

Alveoli collapse because of higher, not lower, pressure requirements when surfactant is absent. Without surfactant, the surface tension increases, making it harder to keep alveoli open during expiration.

B. Alveoli will remain open regardless of size.

Alveoli require surfactant to maintain stability. Without surfactant, smaller alveoli tend to collapse due to excessive surface tension, leading to atelectasis and impaired gas exchange.

D. Larger alveoli will collapse while smaller ones remain stable.

The opposite is true—smaller alveoli are at greater risk of collapse, while larger alveoli, with lower surface tension, are more likely to remain open. This is why surfactant is critical in reducing surface tension differences across alveoli.

Correct Answer C. Inflamed pleural surfaces

Explanation

Pleurisy occurs when the pleura become inflamed and rub against each other, producing a characteristic friction rub on auscultation. The inflammation leads to sharp, localized chest pain that worsens with deep breathing or coughing.

Why Other Options Are Wrong

A. Presence of excess air

Excess air in the pleural space, known as pneumothorax, causes lung collapse but does not typically produce a pleural friction rub. Pneumothorax presents with decreased breath sounds and hyperresonance on percussion rather than a grating sound.

B. Increased pleural fluid

Pleural effusion, or an abnormal accumulation of fluid in the pleural cavity, dampens lung sounds and may cause dullness on percussion. However, it does not create a grating friction rub, as excess fluid separates the pleural surfaces.

D. Thickened bronchial walls

Bronchial wall thickening is associated with conditions like chronic bronchitis and asthma but does not directly relate to pleurisy. Pleurisy affects the pleural linings rather than the bronchial structures.

Correct Answer B. The vocal cords vibrate to produce sound, which is then modified by the mouth and tongue.

Explanation

Sound production occurs when air passes through the glottis and causes the vocal cords to vibrate. The resulting sound waves are shaped into speech by the tongue, lips, and other articulatory structures. Pitch and tone are adjusted by changing the tension and length of the vocal cords.

Why Other Options Are Wrong

A. The vocal cords vibrate to create sound waves that are then amplified by the lungs.

The lungs generate airflow, but they do not amplify sound waves. Sound amplification occurs in the vocal tract, including the pharynx, mouth, and nasal cavity. The lungs mainly serve as the power source for vocalization rather than an amplification chamber.

C. The vocal cords vibrate to filter out unwanted noise from the air.

Vocal cords do not function as noise filters. Their primary role is sound production, while external noises are managed by the auditory system and environmental factors. The brain interprets and filters unwanted noise, not the vocal cords.

D. The vocal cords vibrate to regulate airflow into the trachea.

While the vocal cords can partially close to help regulate airflow (such as during speech or breath-holding), their primary function is sound production. Airflow regulation in the respiratory system is mainly controlled by the diaphragm and bronchial smooth muscles.

Correct Answer A. By filtering and humidifying air before it reaches the lungs

Explanation

The upper airways, including the nasal passages and trachea, serve as the first line of defense against airborne pathogens, dust, and debris. They filter out large particles through nasal hairs and mucus while also humidifying and warming the air to prevent airway irritation. This ensures that the air reaching the lower respiratory tract is clean, moist, and at an optimal temperature for gas exchange.

Why Other Options Are Wrong

B. By directly exchanging gases with the bloodstream

Gas exchange occurs in the alveoli of the lungs, not in the upper airways. The upper airways serve as conduits for airflow and filtration but do not participate in the transfer of oxygen or carbon dioxide between blood and air.

C. By producing mucus that aids in digestion

While mucus is produced in the respiratory tract, its primary function is to trap debris and pathogens rather than aid digestion. The digestive system has its own mucus-producing structures, such as the stomach lining and intestines, separate from the respiratory system.

D. By regulating the temperature of the blood

The respiratory system helps regulate the temperature of inhaled air but does not play a direct role in regulating blood temperature. Blood temperature is primarily maintained by metabolic processes, thermoregulation in the skin, and the hypothalamus.

Correct Answer A. Increased risk of airway obstruction due to mucus buildup.

Explanation

In chronic bronchitis, excess mucus production leads to airway obstruction and a persistent cough, which serves as a mechanism to clear mucus. Suppressing the cough reflex prevents mucus clearance, increasing the risk of airway blockage, infections, and respiratory complications. This can worsen breathing difficulties and contribute to bacterial colonization in stagnant mucus.

Why Other Options Are Wrong

B. Improved lung function due to reduced irritation.

Suppressing the cough may reduce symptoms temporarily, but it does not improve lung function. Instead, mucus accumulates in the airways, worsening airflow obstruction. Over time, the retained secretions can increase inflammation, leading to further deterioration of lung function.

C. Decreased likelihood of respiratory infections.

Retaining mucus actually increases the risk of infections because bacteria and viruses can thrive in mucus-filled airways. Infections such as pneumonia and bacterial bronchitis are more likely when mucus clearance is impaired.

D. Enhanced effectiveness of mucolytic agents.

Mucolytic agents help thin mucus, but their effectiveness depends on an active cough reflex to expel loosened secretions. If the cough reflex is suppressed, even thinner mucus may accumulate and contribute to obstruction rather than improving airway clearance.

Correct Answer B. The accumulation of fluid in the pleural cavity.

Explanation

Pleural effusion occurs when excess fluid collects in the space between the pleura, the membranes surrounding the lungs. This can result from infections, heart failure, cancer, or other conditions that disrupt normal pleural fluid balance. If untreated, it can impair lung expansion and cause breathing difficulties.

Why Other Options Are Wrong

A. A condition characterized by the presence of air in the pleural cavity.

The presence of air in the pleural cavity is known as a pneumothorax, not a pleural effusion. Pneumothorax leads to lung collapse due to the loss of negative pressure, while pleural effusion primarily involves fluid buildup.

C. An infection in the pleural space.

An infection in the pleural space is known as empyema, which is a complication of pneumonia or other infections. While some pleural effusions can be caused by infections, not all are infectious in nature.

D. A type of lung cancer.

Lung cancer can lead to pleural effusion (malignant pleural effusion), but the effusion itself is not a type of cancer. Instead, it is a secondary condition caused by the cancer's impact on pleural fluid dynamics.

Correct Answer D. Covers ~95% of alveolar surface

Explanation

Type II pneumocytes are responsible for surfactant production and can proliferate into type I pneumocytes when needed. However, they do not cover 95% of the alveolar surface—this function belongs to type I pneumocytes, which form the thin epithelial lining for gas exchange.

Why Other Options Are Wrong

A. Synthesize pulmonary surfactants

This statement is true. Type II pneumocytes are the primary source of surfactant, which prevents alveolar collapse and reduces surface tension.

B. Secrete cytokines

This statement is also true. Type II pneumocytes contribute to lung immunity by secreting cytokines, which help regulate inflammation and immune responses.

C. Proliferate into type I cells

Correct as well. Type II cells can differentiate into type I cells when alveolar damage occurs, helping in lung repair and regeneration.

Correct Answer C. Diaphragm

Explanation

The diaphragm is the primary muscle of inspiration, responsible for creating negative intrathoracic pressure that allows air to enter the lungs. Unlike accessory muscles, which assist during forced inspiration, the diaphragm functions in both normal and deep breathing. Accessory muscles, such as the scalene and sternocleidomastoid, are recruited when increased respiratory effort is needed.

Why Other Options Are Wrong

A. Scalene

The scalene muscles assist in inspiration by elevating the first and second ribs, helping to expand the thoracic cavity. They become more active during deep or labored breathing, such as in respiratory distress. Unlike the diaphragm, they are not involved in passive breathing.

B. Sternocleidomastoid

The sternocleidomastoid muscle aids inspiration by elevating the sternum and clavicle, increasing lung volume. It is particularly active during exertion or respiratory distress but does not function as a primary breathing muscle in normal respiration.

D. Trapezius

The trapezius muscle assists in stabilizing the shoulders and upper thorax during deep inhalation. It indirectly supports respiratory function by maintaining posture and allowing efficient use of the accessory muscles. However, it is not directly involved in normal passive inspiration.

Correct Answer B. Increasing fluid intake

Explanation

Adequate hydration is essential for maintaining proper mucociliary function. Increased fluid intake helps keep mucus thin and mobile, allowing cilia to transport debris out of the airways more effectively.

Why Other Options Are Wrong

A. Administering high-flow oxygen

High-flow oxygen can actually dry out mucous membranes, worsening mucociliary dysfunction rather than improving it.

C. Reducing ventilator pressure settings

Lowering ventilator pressure may reduce barotrauma but does not directly improve mucociliary transport.

D. Performing endotracheal suctioning frequently

Frequent suctioning can remove mucus, but it does not improve the function of mucociliary transport itself. It may also cause airway trauma and increase the risk of infection.