Organ
Alveolus
Microscopic air space at the gas-exchange surface
High-yield
The thin part of the air-blood barrier contains alveolar epithelium, closely apposed basement membranes and capillary endothelium. Surfactant reduces surface tension; connective tissue also stabilizes the alveoli.
Overview
Alveoli place inhaled air close to pulmonary capillary blood. Thin type I cells cover most of the air-facing surface, while type II cells supply surfactant and contribute to epithelial repair. Macrophages remove material reaching these spaces.
Reference facts
- Location
- In the gas-exchanging acinus, opening from respiratory bronchioles and alveolar ducts or sacs
- Parts
- Alveolar epithelial cells, macrophages, connective-tissue septa and a dense capillary network
- Blood supply
- Pulmonary capillaries closely associated with alveolar walls
- Innervation
- No skeletal motor supply; pulmonary visceral afferents sense mechanical and chemical changes in the distal lung
- Venous/Lymphatic drainage
- Capillary blood returns through pulmonary venules; interstitial fluid reaches pulmonary lymphatic networks, including sparse deep intralobular channels
- Function
- Diffusion of oxygen and carbon dioxide across a short air-blood distance
Clinical correlation
Surfactant deficiency makes alveoli harder to keep open. Damage to the epithelial-endothelial barrier allows fluid accumulation and impairs gas exchange.
Frequently asked questions
Where is the alveolus located?
In the gas-exchanging acinus, opening from respiratory bronchioles and alveolar ducts or sacs.
What does the alveolus do?
Diffusion of oxygen and carbon dioxide across a short air-blood distance.
What are the parts of the alveolus?
The parts of the alveolus are the alveolar epithelial cells, macrophages, connective-tissue septa and a dense capillary network.
What is the blood supply of the alveolus?
The alveolus is supplied by the pulmonary capillaries closely associated with alveolar walls.