Which of the following BEST describes what alveoli are?

Step 1: Define the Problem

Identify the key components of the question that need to be addressed:

• The question asks for a description of what alveoli are.
• It is a multiple-choice question, so we need to determine the best description.

Step 2: Break Down the Problem

Divide the problem into smaller, manageable parts:

• Understand the function and structure of alveoli.
• Compare the characteristics of alveoli with the given options.

Step 3: Apply Relevant Concepts

Use appropriate academic theories or formulas to solve each part of the problem:

• Alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place.
• They are crucial for the respiratory system, providing a large surface area for gas exchange.

Step 4: Analysis, Verify and Summarize

Analyze each part in detail if necessary, carry out the calculations by steps. Verify the calculations result and summarize the findings:

• Alveoli are essential for breathing and are located at the end of the respiratory tree.
• They are surrounded by capillaries and have thin walls to facilitate gas exchange.

Final Answer

The alveoli are best described as tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide occurs.