Alveoli

Definition

Alveoli are tiny air sacs located in the lungs where the exchange of oxygen and carbon dioxide takes place. These structures are crucial for effective respiration, allowing oxygen to enter the bloodstream and carbon dioxide to be expelled from the body. Their large surface area and thin walls facilitate this gas exchange process, playing a vital role in maintaining respiratory efficiency.

5 Must Know Facts For Your Next Test

1. There are approximately 300 million alveoli in a healthy adult human lung, providing a massive surface area for gas exchange, roughly the size of a tennis court.
2. Alveoli are lined with a thin layer of epithelial cells, which allows for efficient diffusion of gases due to their minimal thickness.
3. The process of gas exchange in the alveoli is driven by concentration gradients; oxygen moves from the air in the alveoli to the blood, while carbon dioxide moves from the blood into the alveoli.
4. Damage to the alveoli, such as from smoking or certain diseases like emphysema, can significantly impair lung function and reduce oxygen supply to the body.
5. In addition to gas exchange, alveoli also play a role in filtering out small particles from inhaled air and contributing to immune defense mechanisms within the lungs.

Review Questions

• How do alveoli contribute to effective gas exchange in the lungs?
  • Alveoli contribute to effective gas exchange by providing a vast surface area and thin walls that facilitate the diffusion of oxygen into the bloodstream and carbon dioxide out of it. The design of alveoli maximizes contact with pulmonary capillaries, ensuring that oxygen can quickly enter circulation while carbon dioxide is removed. This process is critical for maintaining proper oxygen levels in the body and ensuring that carbon dioxide is expelled efficiently.
• Discuss how surfactant affects alveolar function and what happens when surfactant levels are inadequate.
  • Surfactant is a substance that coats the inner surfaces of alveoli, reducing surface tension and preventing their collapse during exhalation. When surfactant levels are inadequate, as seen in conditions like Neonatal Respiratory Distress Syndrome, alveoli can collapse, leading to decreased lung compliance and impaired gas exchange. This not only affects oxygen uptake but can also result in serious respiratory complications, highlighting surfactant's essential role in normal lung function.
• Evaluate the implications of damaged alveoli on overall respiratory health and systemic function.
  • Damaged alveoli can severely impact respiratory health by limiting gas exchange efficiency, resulting in lower oxygen levels and higher carbon dioxide levels in the blood. Conditions such as chronic obstructive pulmonary disease (COPD) or emphysema lead to destruction of alveolar walls, reducing their number and functionality. This impairment not only affects breathing but can also lead to systemic issues such as fatigue, reduced exercise capacity, and increased strain on the heart due to insufficient oxygen delivery throughout the body.

Related terms

Bronchioles: Small air passages that branch off from the bronchi and lead to the alveoli, playing a key role in directing air flow within the lungs.

Surfactant: A substance produced by the alveoli that reduces surface tension, preventing the collapse of these air sacs during exhalation.

Pulmonary Capillaries: Tiny blood vessels that surround the alveoli, where oxygen and carbon dioxide are exchanged between the air in the alveoli and the blood.