Bronchi → Bronchioles → Alveoli
The bronchi are the airways that lead from the trachea into the lungs and then branch off into progressively smaller structures until they reach the alveoli, the tiny sacs that allow for the exchange of oxygen and carbon dioxide in the lungs. The bronchi are made up of cartilage, smooth muscle, and mucous membranes.
- The bronchi function primarily as a passageway for air to travel from the mouth and trachea, down to the alveoli, and back out of the body.
The bronchioles are tubes in the lungs that branch off from the larger bronchi that enter each lung, from the large and singular trachea which connects to the mouth—the bronchioles different units of the lungs or pulmonary lobules. The bronchioles continue dividing into smaller terminal bronchioles, which divide into the smallest respiratory bronchioles.
- The bronchioles serve as a transition between the large cartilage supported bronchi that enter the lungs and the tiny alveolar ducts that connect directly to the alveoli.
- The bronchioles carry oxygen-rich air into the lungs and carry carbon dioxide-rich air out of the lungs.
Alveoli are tiny air sacs in your lungs that take up the oxygen you breathe in and keep your body going. The alveoli consist of an epithelial layer of simple squamous epithelium (fragile, flattened cells) and an extracellular matrix surrounded by capillaries.
- Alveoli are an important part of the respiratory system whose function is to exchange oxygen and carbon dioxide molecules to and from the bloodstream.