Which statement accurately describes the alveolar-capillary membrane’s primary function?

Which statement accurately describes the alveolar-capillary membrane’s primary function?

• A. Filters bacteria from the blood
• B. Facilitates gas exchange between air and blood
• C. Prevents the entry of immune cells into the lungs
• D. Stores oxygen for later use

Answer: (B)

The primary function of the alveolar-capillary membrane is to facilitate gas exchange between air and blood. This thin membrane is located in the lungs where the alveoli (air sacs) come into close contact with the capillaries (small blood vessels) surrounding them. The design of this membrane enables efficient diffusion of gases. Oxygen from the inhaled air passes through the alveolar membrane into the blood in the capillaries, while carbon dioxide in the blood diffuses in the opposite direction to be exhaled. This process is essential for respiration, as it ensures that oxygen enters the bloodstream to be delivered to tissues throughout the body, while simultaneously allowing carbon dioxide, a waste product of metabolism, to be expelled. The simplicity and thinness of the alveolar-capillary membrane are crucial in maintaining this rapid exchange due to a minimal barrier that enables gases to cross easily. The other options pertain to different functions or misconceptions; for instance, the membrane does not filter bacteria or prevent immune cells from entering the lungs. Additionally, it does not store oxygen, but rather plays a role in the immediate exchange of gases, which is pivotal for maintaining proper respiratory function and homeostasis within the body.

The primary function of the alveolar-capillary membrane is to facilitate gas exchange between air and blood. This thin membrane is located in the lungs where the alveoli (air sacs) come into close contact with the capillaries (small blood vessels) surrounding them. The design of this membrane enables efficient diffusion of gases. Oxygen from the inhaled air passes through the alveolar membrane into the blood in the capillaries, while carbon dioxide in the blood diffuses in the opposite direction to be exhaled.

This process is essential for respiration, as it ensures that oxygen enters the bloodstream to be delivered to tissues throughout the body, while simultaneously allowing carbon dioxide, a waste product of metabolism, to be expelled. The simplicity and thinness of the alveolar-capillary membrane are crucial in maintaining this rapid exchange due to a minimal barrier that enables gases to cross easily.

The other options pertain to different functions or misconceptions; for instance, the membrane does not filter bacteria or prevent immune cells from entering the lungs. Additionally, it does not store oxygen, but rather plays a role in the immediate exchange of gases, which is pivotal for maintaining proper respiratory function and homeostasis within the body.