Alveoli

Definition

Alveoli are tiny air sacs located in the lungs that facilitate the exchange of oxygen and carbon dioxide between the air and the bloodstream. They are the primary site for gas exchange due to their large surface area and thin walls, which allow for efficient diffusion of gases. Their structure is crucial for respiratory function, as they ensure that oxygen can be absorbed into the blood while carbon dioxide is expelled.

5 Must Know Facts For Your Next Test

1. Alveoli are estimated to number around 300 million in the human lungs, providing an enormous surface area of approximately 70 square meters for gas exchange.
2. The walls of the alveoli are only one cell thick, which allows for efficient diffusion of gases into and out of the bloodstream.
3. Alveoli are lined with surfactant, which helps keep them open and reduces the work required for breathing by lowering surface tension.
4. Gas exchange in the alveoli occurs via passive diffusion; oxygen moves from the air in the alveoli into the blood, while carbon dioxide moves from the blood into the alveoli.
5. Damage to the alveoli, such as in conditions like emphysema, significantly impairs respiratory function and gas exchange efficiency.

Review Questions

• How do alveoli contribute to effective gas exchange in the lungs?
  • Alveoli contribute to effective gas exchange by providing a large surface area for oxygen and carbon dioxide to diffuse across. Their thin walls, made of a single layer of cells, enable gases to pass quickly and efficiently between the air and bloodstream. The presence of pulmonary capillaries surrounding each alveolus further enhances this process by allowing oxygen to enter the blood and carbon dioxide to be expelled.
• Discuss how surfactant impacts alveolar function and overall respiratory health.
  • Surfactant is crucial for maintaining proper alveolar function because it reduces surface tension within the alveoli. This prevents their collapse during exhalation, ensuring they remain open and ready for gas exchange. A deficiency in surfactant can lead to conditions such as neonatal respiratory distress syndrome or acute respiratory distress syndrome (ARDS), highlighting its importance in overall respiratory health.
• Evaluate the implications of compromised alveolar function on systemic health and disease progression.
  • Compromised alveolar function can significantly affect systemic health as it disrupts normal gas exchange processes. Conditions like chronic obstructive pulmonary disease (COPD) or pulmonary fibrosis lead to reduced oxygen intake and impaired carbon dioxide removal, which can cause systemic hypoxia or respiratory acidosis. Over time, this may exacerbate cardiovascular problems and increase morbidity due to insufficient oxygenation of tissues throughout the body.

Related terms

Bronchioles: Small branches of the bronchi that lead directly to the alveoli, playing a key role in directing air to these tiny air sacs.

Surfactant:

A substance produced by type II alveolar cells that reduces surface tension in the alveoli, preventing their collapse and making breathing easier.

Pulmonary Capillaries: Tiny blood vessels that surround the alveoli, facilitating the exchange of gases as blood passes through them.