Alveoli

Definition

Alveoli are tiny air sacs located in the lungs where the exchange of oxygen and carbon dioxide takes place. They are crucial for respiration because they provide a large surface area for gas exchange, enabling oxygen to enter the bloodstream while removing carbon dioxide from it. The efficiency of this process is vital, especially during physical activity when the body's demand for oxygen increases significantly.

5 Must Know Facts For Your Next Test

1. Each lung contains about 300 million alveoli, providing a vast surface area of approximately 70 square meters for gas exchange.
2. Alveoli are surrounded by capillaries, which facilitate the transfer of gases between the air in the alveoli and the blood.
3. During exercise, the increased demand for oxygen leads to a higher rate of breathing and greater ventilation of the alveoli.
4. Diseases such as emphysema can damage alveoli, significantly impairing their function and reducing oxygen intake during physical activity.
5. The structure of alveoli includes elastic fibers that allow them to expand and contract, which is essential for maintaining airflow during breathing.

Review Questions

• How do alveoli contribute to the efficiency of gas exchange during exercise?
  • Alveoli significantly enhance gas exchange efficiency due to their vast surface area and proximity to capillaries. During exercise, the body requires more oxygen, prompting an increase in breathing rate and depth. This means more air reaches the alveoli, allowing for optimal oxygen uptake and carbon dioxide removal, which is crucial for sustaining physical performance.
• What role does surfactant play in maintaining alveolar function, particularly during intense exercise?
  • Surfactant is a critical substance produced by alveoli that lowers surface tension within these air sacs. During intense exercise, as breathing rates increase, surfactant helps prevent alveolar collapse by ensuring they remain open and functional. This is vital for effective gas exchange under higher respiratory demands, enabling athletes to maintain optimal performance.
• Evaluate how damage to the alveoli affects overall respiratory function and exercise capacity.
  • Damage to the alveoli, such as that caused by conditions like emphysema or pulmonary fibrosis, greatly impairs respiratory function. This leads to reduced surface area for gas exchange, limiting oxygen uptake and increasing carbon dioxide retention. As a result, individuals with damaged alveoli experience decreased exercise capacity due to insufficient oxygen supply during physical activity, ultimately affecting their endurance and performance.

Related terms

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

Surfactant: A substance produced by the alveoli that reduces surface tension within the air sacs, preventing their collapse and ensuring efficient gas exchange.

Respiratory Membrane: The thin barrier composed of alveolar and capillary walls where gas exchange occurs, allowing oxygen to diffuse into the blood and carbon dioxide to diffuse out.