Organ
Bronchioles
Small airways without supporting cartilage
High-yield
A terminal bronchiole ends the conducting pathway; its downstream acinus contains respiratory bronchioles, alveolar ducts and alveoli.
Overview
Bronchioles continue the airway tree after the smallest bronchi. Their walls contain smooth muscle but lack cartilage and submucosal glands. Terminal bronchioles lead to respiratory bronchioles, where alveoli begin to interrupt the airway wall.
Reference facts
- Location
- Within the lung beyond the small cartilaginous bronchi
- Parts
- Conducting and terminal bronchioles, followed by respiratory bronchioles and alveolar ducts
- Blood supply
- Bronchial and pulmonary microvascular connections in the distal airway region
- Innervation
- Vagal cholinergic input influences muscle tone; beta-adrenergic relaxation is not evidence of abundant direct sympathetic muscle innervation
- Relations
- Low columnar or cuboidal epithelium including club cells; smooth-muscle walls without cartilage or submucosal glands
- Function
- Distribute airflow; respiratory bronchioles also contribute to gas exchange
Clinical correlation
Small-airway narrowing, mucus and loss of surrounding alveolar attachments contribute to airflow limitation in COPD. Emphysema and airway remodeling can contribute in different proportions.
Frequently asked questions
Where are the bronchioles located?
Within the lung beyond the small cartilaginous bronchi.
What do the bronchioles do?
Distribute airflow; respiratory bronchioles also contribute to gas exchange.
What are the parts of the bronchioles?
The parts of the bronchioles are the conducting and terminal bronchioles, followed by respiratory bronchioles and alveolar ducts.
What is the blood supply of the bronchioles?
The bronchioles are supplied by the bronchial and pulmonary microvascular connections in the distal airway region.