Alveoli

Definition

Alveoli are tiny air sacs located in the lungs where gas exchange occurs between the air and the bloodstream. These structures play a crucial role in respiratory physiology, allowing oxygen to enter the blood and carbon dioxide to be expelled from the body. Their large surface area and thin walls facilitate efficient diffusion of gases, making them essential for effective respiratory function.

5 Must Know Facts For Your Next Test

1. Each lung contains approximately 300 million alveoli, providing a massive surface area of about 70 square meters for gas exchange.
2. Alveoli are lined with a thin layer of epithelial cells, allowing for rapid diffusion of oxygen and carbon dioxide between the air and blood.
3. The structure of alveoli is essential for their function; they have a spherical shape which maximizes surface area and minimizes wall thickness.
4. Alveolar walls contain elastic fibers that allow them to stretch during inhalation and recoil during exhalation, facilitating efficient breathing.
5. Alveolar health is vital; conditions such as pneumonia or pulmonary edema can lead to impaired gas exchange and respiratory failure.

Review Questions

• How do alveoli contribute to the overall efficiency of gas exchange in the lungs?
  • Alveoli enhance gas exchange efficiency due to their vast surface area and thin walls. The large number of alveoli in each lung creates a significant area for oxygen to diffuse into the bloodstream and for carbon dioxide to exit. The close proximity of pulmonary capillaries surrounding the alveoli also facilitates quick gas exchange, ensuring that the body receives sufficient oxygen while removing carbon dioxide effectively.
• Discuss the role of surfactant in maintaining alveolar function and how its deficiency can impact respiratory health.
  • Surfactant plays a crucial role in maintaining alveolar function by reducing surface tension within the alveoli. This allows them to remain open during breathing, preventing collapse. A deficiency in surfactant can lead to conditions like Respiratory Distress Syndrome, particularly in premature infants, resulting in decreased lung compliance, impaired gas exchange, and increased work of breathing.
• Evaluate the impact of diseases like emphysema on alveolar structure and function, and how this relates to overall respiratory efficiency.
  • Diseases like emphysema significantly alter alveolar structure by destroying their walls, leading to larger but fewer air sacs. This reduction in surface area drastically decreases gas exchange efficiency as there are fewer locations for oxygen uptake and carbon dioxide removal. Consequently, patients experience shortness of breath and reduced exercise tolerance, highlighting how crucial healthy alveoli are for effective respiration.

Related terms

pulmonary capillaries: Small blood vessels that surround the alveoli, allowing for the exchange of oxygen and carbon dioxide between the air in the alveoli and the blood.

surfactant: A substance produced by alveolar cells that reduces surface tension within the alveoli, preventing collapse and aiding in lung expansion during breathing.

respiration: The process of gas exchange that occurs in the lungs, involving inhalation of oxygen and exhalation of carbon dioxide.