Alveoli

Definition

Alveoli are tiny air sacs in the lungs that play a crucial role in gas exchange. These structures are where oxygen from inhaled air enters the bloodstream, and carbon dioxide from the blood is expelled. The large surface area provided by millions of alveoli enhances the efficiency of gas exchange, making them essential for respiratory function.

5 Must Know Facts For Your Next Test

1. Alveoli are surrounded by a network of capillaries, which allows for efficient gas exchange between air and blood.
2. The walls of the alveoli are extremely thin, facilitating rapid diffusion of gases.
3. Each lung contains approximately 300 million alveoli, providing a massive surface area for gas exchange, roughly the size of a tennis court.
4. Alveoli also contain specialized cells called type II pneumocytes that produce surfactant to keep them open and functional.
5. In certain conditions like pneumonia or pulmonary edema, fluid can accumulate in the alveoli, impairing gas exchange and leading to respiratory distress.

Review Questions

• How do the structural features of alveoli enhance their function in gas exchange?
  • The structure of alveoli significantly enhances their function in gas exchange through several key features. First, their large number creates a vast surface area, which maximizes exposure to incoming air. Additionally, the thin walls of the alveoli allow for rapid diffusion of gases; oxygen can quickly move into the blood while carbon dioxide exits. The close proximity of surrounding capillaries further facilitates this process, making gas exchange efficient and effective.
• Discuss the importance of surfactant in maintaining healthy alveolar function and how its deficiency can impact respiratory health.
  • Surfactant is crucial for maintaining healthy alveolar function as it reduces surface tension within the alveoli, preventing them from collapsing during exhalation. Without adequate surfactant, as seen in conditions like neonatal respiratory distress syndrome, alveoli may collapse (atelectasis), leading to decreased lung compliance and impaired gas exchange. This deficiency can result in significant respiratory distress and requires medical intervention to support breathing.
• Evaluate the impact of diseases such as COPD and pneumonia on alveolar function and overall respiratory health.
  • Diseases like COPD and pneumonia have a profound impact on alveolar function and respiratory health. In COPD, chronic inflammation and damage to alveolar walls lead to decreased surface area for gas exchange and reduced airflow, causing difficulty in breathing. Pneumonia can fill alveoli with fluid or pus, obstructing airflow and impairing gas exchange. Both conditions significantly hinder the lungs' ability to oxygenate blood efficiently, leading to serious health complications and diminished quality of life.

Related terms

Bronchioles: Small air passages that branch from the bronchi and lead to the alveoli, playing a key role in directing air to the gas exchange sites.

Surfactant: A substance produced by alveolar cells that reduces surface tension within the alveoli, preventing their collapse and facilitating easier breathing.

Capillaries:

Tiny blood vessels that surround the alveoli, allowing for the exchange of oxygen and carbon dioxide between the air in the alveoli and the blood.