Tracheobronchial tree
- Used to refer to the airways leading to the lungs
- Airways look like an upside down tree
Trachea
- 10-12 cm long
- Located midline in the neck
- Supported anteriorly by cartilage
Carina
Area just before the trachea divides into the right and left main-stem bronchus.
Right main-stem bronchus
- Branches off the trachea at a 25 degree angle
- Problem during intubation because the endotracheal tube can easily get pushed into the right main stem where it doesn't belong
- Supported by cartilage
Left main-stem bronchus
- Branches off the trachea at a 40-60 degree angle
- Supported by cartilage
Lobar bronchi
- Large air passages that direct gas to the upper, middle, and lower lobes of the lungs
- Supported by cartilage
Segmental bronchi
- Large air passages that further direct the gases to specific segments in each lobe of the lung
- 10 in the right lung
- 8 in the left lung
- Supported by cartilage
Sub-segmental bronchi
- Airways become progressively smaller
- Supported by cartilage
Bronchioles
- Small airways less than 1 mm in diameter
- Not supported by cartilage
Terminal bronchioles
- End of the conducting airways
- Canals of Lambert (pathways for collateral ventilation)
- Secondary avenue for collateral ventilation in patients
- Not supported by cartilage
Collateral ventilation
Alternate route.
Histology of the tracheobronchial tree
Consists of three layers:
1. Epithelial lining.
2. Lamina propria.
3. Cartilaginous layer.
Epithelial lining
- Made of pseudostratified ciliated columnar cells
- 200 cilia per cell
Cilia
- Hair-like structures that move in waves to remove particles
- None past the terminal bronchioles
Mucous layer/blanket
- Covers the epithelial lining of the tracheobronchial tree
- Goblet cells, submucosal glands, and bronchial glands produce mucous
- Consists of a gel/sol layer
Gel/sol layer
- Where particles are caught
- Cilia move in this less viscous layer
Mucocilliary transport/escalator
- Term given to cilia moving in a wavelike fashion to move particles at a rate of 2 cm per minute
Lamina propria
- Submucosal layer
Consists of:
1. Branches of the vagus nerve.
2. Smooth muscle fiber (when they constrict, they squeeze the airway and the patient wheezes).
3. Mast cells.
Mast cells
- Play an important role in the immunologic mechanism
- Release histamine and leukotrienes