Podcast
Questions and Answers
What is the primary function of the alveoli in the lungs?
What is the primary function of the alveoli in the lungs?
Which feature of the alveoli aids in efficient gas exchange?
Which feature of the alveoli aids in efficient gas exchange?
What is the role of capillaries in the alveolar structure?
What is the role of capillaries in the alveolar structure?
How does the thickness of the walls in alveoli and capillaries contribute to gas exchange?
How does the thickness of the walls in alveoli and capillaries contribute to gas exchange?
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What happens to oxygen after it diffuses from the alveoli into the blood?
What happens to oxygen after it diffuses from the alveoli into the blood?
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What is the total surface area of the alveoli in the lungs approximately?
What is the total surface area of the alveoli in the lungs approximately?
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Which condition is met by the presence of a thin film of moisture lining the alveoli?
Which condition is met by the presence of a thin film of moisture lining the alveoli?
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How many alveoli are estimated to exist in one human lung?
How many alveoli are estimated to exist in one human lung?
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Study Notes
Gaseous Exchange
- Gaseous exchange is the movement of oxygen from the lungs into the blood and carbon dioxide from the blood to the lungs.
- This vital process occurs in the lungs between alveoli and capillaries.
- Capillaries line approximately 70% of the alveoli, creating a large surface area for gas diffusion.
The Alveoli
- The alveoli are the site of gaseous exchange.
- Alveoli are adapted for efficient gas exchange due to their small size (approximately 300 µm in diameter), resulting in a high surface area-to-volume ratio (around 70 square metres).
- Another crucial adaptation is the enormous number of alveoli (approximately 700 million, with 350 million in each lung).
- A short diffusion path—one cell thick walls, moistened with a thin fluid— further enhances gas exchange efficiency.
Structure of Alveoli
- The image shows blood from pulmonary arteries entering the delicate capillary network enveloping the alveoli. Air moves into and out of the alveoli.
- Blood leaves the alveoli as oxygenated blood through the pulmonary veins.
- The complex structure ensures rapid and efficient gas exchange.
How Gaseous Exchange Occurs
- Oxygen moves from the lungs to the blood, while carbon dioxide moves from the blood to the lungs, occurring in the alveoli and associated capillaries.
- The alveoli’s thin walls allow gases to pass between air and blood.
- Oxygen diffuses from the alveoli into the blood, attaching to red blood cells.
- Carbon dioxide diffuses from the blood into the alveoli to be exhaled.
- This process is essential for life as it provides the body with oxygen and removes waste carbon dioxide.
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