Lungs and Ventilation - LO 3
3. Diagram the airway path – i.e., tracheobronchial tree – from trachea to segmental bronchi. Identify cartilages associated with creating an emergency airway.
Any of the airway path inferior to the larynx is considered a component of the tracheobronchial tree. The larynx transitions into the trachea (trunk of tracheobronchial tree) at the inferior border of the cricoid cartilage (approximately C6-level). The bifurcation of the trachea into a right and left main bronchus occurs at the level of the sternal angle. There are important differences between the R. and L. main bronchi, including:
Right main bronchus: more vertical in orientation, wider, and shorter
Aspirated materials are more likely to enter into the R. main bronchus (and certain branches) due to its orientation.
Left main bronchus: more horizontal in orientation and longer
The R. and L. main bronchi enter the hila of the lungs. Further branching occurs within the parenchyma of the lungs.
The first set of branching within the lungs is into secondary (lobar) bronchi, which are associated with the lobes of the lungs. Therefore, there are 3 right, secondary (lobar) bronchi and 2 left, secondary (lobar) bronchi.
Secondary (lobar) bronchi further branch into tertiary (segmental) bronchi, which will serve the bronchopulmonary segments. There are 10 tertiary (segmental) bronchi associated with the right lung, and typically 8 (and sometimes up to 10) tertiary (segmental) bronchi for the left lung. If an individual is supine and the aspirated material is small enough, it is more likely to lodge in the superior segmental bronchus of the R. inferior lobe, due to the posterior direction of this segment.
The rest of the tracheobronchial tree branching occurs at a level that is difficult/impossible to see at a gross level.
Tertiary (segmental) bronchi → conducting bronchioles → terminal bronchioles → respiratory bronchioles → alveolar ducts → alveolar sacs
Emergency Airways
Tracheostomy: incision through the anterior neck and trachea typically between the 1st and 2nd tracheal rings and occasionally more inferior. A tracheostomy tube is entered through the incision to establish an airway
Cricothyrotomy: for a more emergent situation, an incision is made through the anterior neck and median cricothyroid ligament (between the thyroid and cricoid cartilages) for immediate entry of air.
