Respiratory System Function: TEAS Practice Question with Answer & Explanation

Understanding the Role of the Alveoli

To answer this question correctly, you must understand the primary function of the respiratory system's functional unit: the alveolus. The lungs contain millions of these tiny, grape-like air sacs. Their wall structure is incredibly thin—only one cell thick—which allows for the efficient diffusion of gases (oxygen and carbon dioxide) between the air in the lungs and the blood in the surrounding capillaries.

Why Choice B is Correct

The principle of gas exchange relies heavily on surface area. Think of the alveoli like a sponge; the more tiny holes and surfaces there are, the more "work" (gas exchange) the sponge can do. When the walls between the alveoli break down (as seen in conditions like emphysema), several small sacs merge into one larger, less efficient sac. This reduces the total surface area available for oxygen to enter the blood and carbon dioxide to leave it. Therefore, a decrease in surface area is the direct physiological result of alveolar damage.

Analysis of Incorrect Choices

• Choice A: If the alveoli are damaged, the diffusion of carbon dioxide into the bloodstream would decrease, not increase. Furthermore, carbon dioxide actually diffuses out of the bloodstream and into the alveoli to be exhaled.
• Choice C: The diaphragm is a muscle located at the base of the thoracic cavity. While alveolar damage makes breathing difficult, it does not physically prevent the diaphragm from contracting. The diaphragm's function is controlled by the phrenic nerve and the brainstem, not the lung tissue itself.
• Choice D: Alveolar damage affects the efficiency of gas exchange, but it does not stop the heart from pumping blood through the pulmonary artery. Blood will still flow to the lungs, but it will not be able to pick up enough oxygen once it gets there.

TEAS Concept: Gas Exchange

On the TEAS, you are expected to know the pathway of air and the mechanics of the "respiratory membrane." The respiratory membrane consists of the alveolar epithelium and the capillary endothelium. Any pathology that thickens this membrane (like fluid in pneumonia) or destroys it (like emphysema) will lead to hypoxemia (low blood oxygen).

Memory Tip

Think: "Alveoli = Area." The Alveoli provide the Area for gas exchange. If you damage the Alveoli, you lose the Area. No area = No oxygen!