Human Respiratory System

Which of the following is NOT part of the human respiratory system?

• A. Lungs

• B. Trachea

• C. Stomach

• D. Diaphragm

Answer explanation

The stomach is part of the digestive system, not the respiratory system. The lungs, trachea, and diaphragm are all essential components of the human respiratory system.

What is the main function of the alveoli in the respiratory system?

• A. Pump oxygen into the blood

• B. Exchange gases between the air and blood

• C. Remove carbon dioxide from the body

• D. Trap dust and bacteria

Answer explanation

The main function of the alveoli is to exchange gases between the air and blood. They facilitate the transfer of oxygen into the blood and the removal of carbon dioxide, making option B the correct choice.

What happens to the diaphragm during inhalation?

• A. It moves up

• B. It moves down

• C. It stays still

• D. It becomes rigid

Answer explanation

During inhalation, the diaphragm contracts and moves downwards, increasing the thoracic cavity's volume and allowing air to flow into the lungs. Therefore, the correct answer is B. It moves down.

Which gas is inhaled in the highest percentage during breathing?

• A. Oxygen

• B. Carbon dioxide

• C. Nitrogen

• D. Helium

Answer explanation

Nitrogen is the most abundant gas in the atmosphere, making up about 78% of the air we breathe. While oxygen is essential for respiration, nitrogen is inhaled in the highest percentage.

How does the body control the breathing process?

• A. By the heart

• B. By the lungs directly

• C. By the brainstem

• D. By muscle memory

Answer explanation

The body controls the breathing process primarily through the brainstem, which regulates the rhythm and depth of breathing automatically, responding to carbon dioxide levels in the blood.

Which of the following correctly describes the changes in air pressure and thoracic volume during inhalation?

• A. Air pressure increases, thoracic volume decreases

• B. Air pressure decreases, thoracic volume increases

• C. Air pressure increases, thoracic volume increases

• D. Air pressure decreases, thoracic volume decreases

Answer explanation

During inhalation, the diaphragm contracts, increasing thoracic volume. This expansion lowers air pressure in the thoracic cavity, allowing air to flow in. Thus, the correct choice is B: air pressure decreases, thoracic volume increases.

During an experiment comparing inhaled and exhaled air, which gas would show a significant increase in exhaled air?

• A. Oxygen

• B. Nitrogen

• C. Carbon dioxide

• D. Helium

Answer explanation

Inhaled air has a higher concentration of oxygen and nitrogen, while exhaled air contains more carbon dioxide due to cellular respiration. Thus, carbon dioxide shows a significant increase in exhaled air.

Which structure ensures that food does not enter the respiratory system during swallowing?

• A. Trachea

• B. Epiglottis

• C. Larynx

• D. Bronchi

Answer explanation

The epiglottis is a flap of tissue that covers the trachea during swallowing, preventing food from entering the respiratory system. This ensures that food goes down the esophagus instead.

Why is it recommended to breathe through your nose rather than your mouth during exercise?

• A. Breathing through the nose decreases lung activity.

• B. Breathing through the nose increases oxygen levels in the air.

• C. The mouth cannot exhale carbon dioxide effectively.

• D. The nose filters, warms, and humidifies the air.

Answer explanation

Breathing through the nose is recommended during exercise because it filters, warms, and humidifies the air, making it more suitable for the lungs. This helps improve overall respiratory efficiency.

A person living in a city with high air pollution might experience difficulty breathing over time. What is the most likely reason?

• A. Carbon dioxide levels are too high for the lungs to expel.

• B. Particulate matter damages the alveoli, reducing gas exchange efficiency.

• C. Oxygen is entirely replaced by pollutants in the air.

• D. The diaphragm becomes paralyzed in polluted environments.

Answer explanation

B is correct because particulate matter can damage the alveoli in the lungs, which impairs gas exchange and leads to difficulty breathing over time. The other options do not accurately describe the effects of air pollution.