3.3.2 Gas exchange: Human Gas Exchange System

What is the primary function of the alveoli in the human gas exchange system?

• To filter dust and particles from inhaled air

• To provide a large surface area for gas exchange

• To humidify and warm the air

• To transport oxygen to the bloodstream

Answer explanation

The primary function of the alveoli is to provide a large surface area for gas exchange, allowing efficient transfer of oxygen and carbon dioxide between the lungs and bloodstream.

Which structure connects the trachea to the lungs?

• Alveoli

• Bronchioles

• Bronchi

• Diaphragm

Answer explanation

The bronchi are the main passageways that connect the trachea to the lungs. They branch off from the trachea and lead directly into each lung, allowing air to flow in and out.

What role does the diaphragm play in the mechanism of breathing?

• It contracts to increase the volume of the thoracic cavity

• It relaxes to decrease the volume of the thoracic cavity

• It filters air entering the lungs

• It exchanges gases with the blood

Answer explanation

The diaphragm contracts during inhalation, increasing the volume of the thoracic cavity. This decrease in pressure allows air to flow into the lungs, making it essential for the breathing process.

Which muscles work antagonistically to aid in breathing?

• Abdominal and pectoral muscles

• External and internal intercostal muscles

• Diaphragm and triceps

• Quadriceps and hamstrings

Answer explanation

The external and internal intercostal muscles work antagonistically during breathing. The external intercostals help expand the ribcage during inhalation, while the internal intercostals assist in forced exhalation.

What is the equation for pulmonary ventilation rate (PVR)?

• PVR = breathing rate + tidal volume

• PVR = tidal volume × breathing rate

• PVR = tidal volume ÷ breathing rate

• PVR = breathing rate - tidal volume

Answer explanation

The pulmonary ventilation rate (PVR) is calculated by multiplying the tidal volume (the amount of air per breath) by the breathing rate (number of breaths per minute). Thus, the correct equation is PVR = tidal volume × breathing rate.

If the tidal volume is 500 mL and the breathing rate is 15 breaths per minute, what is the pulmonary ventilation rate?

• 7,500 mL/min

• 5,000 mL/min

• 10,000 mL/min

• 15,000 mL/min

Answer explanation

To find the pulmonary ventilation rate, multiply tidal volume (500 mL) by breathing rate (15 breaths/min). 500 mL/breath * 15 breaths/min = 7,500 mL/min, which is the correct answer.

What is the primary function of the trachea in the respiratory system?

• To exchange gases with the blood

• To transport air to the bronchi

• To absorb oxygen into the bloodstream

• To produce mucus

Answer explanation

The primary function of the trachea is to transport air to the bronchi, allowing for airflow to the lungs. It does not exchange gases, absorb oxygen, or produce mucus as its main role.

Which of the following best describes the alveolar epithelium?

• Thick and muscular

• Thin and permeable

• Rigid and inflexible

• Dense and fibrous

Answer explanation

The alveolar epithelium is characterized as thin and permeable, allowing for efficient gas exchange in the lungs. This property is essential for oxygen and carbon dioxide diffusion, making it the best description.

What happens to the pressure in the thoracic cavity when the diaphragm contracts?

• It increases

• It decreases

• It remains the same

• It fluctuates

Answer explanation

When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity. According to Boyle's law, as volume increases, pressure decreases. Therefore, the pressure in the thoracic cavity decreases.

Which of the following is NOT a part of the human gas exchange system?

• Alveoli

• Bronchioles

• Esophagus

• Trachea

Answer explanation

The esophagus is part of the digestive system, not the gas exchange system. The alveoli, bronchioles, and trachea are all essential components involved in the process of gas exchange in the lungs.