Station 1 and 2 Flashcards
At what vertebral levels does the trachea start and end?
Begins at termination of the larynx and C6/7 and terminates as it bifurcates into the L and R primary bronchi (at the carina) at the T4/5 plane (also the level of the sternal angle)
What structures are anterior to the trachea in the neck?
Isthmus of the thyroid gland, strap muscles, steinocleinomastoids. *Recurrent laryngeal nerves ascend the neck either side of the trachea
Where is a tracheotomy performed?
Between C rings 2 and 3, or 3 and 4
What structures are anterior to the trachea in the superior mediastinum?
The manibrium, the thymus, the arch of aorta and its branches (the brachipcephalic trunk, and then the left common carotid and subclavian are more to the left), the SVC, the left and right brachipcephalic veins, fat
What structures lie posterior to the trachea, in both the neck and superior mediastinum?
The oesophagus and the cervical and thoracic vertebrae.
What type of epithelium is in the trachea>
Respiratory epithelium
How many tracheal rings are there?
16-20
What is the functional significance of the C-shaped cartilage rings remaining open posteriorly?
They are closed posteriorly by the trachealis muscle (smooth muscle). Allows ithe oesophagus to bulge out into the tracheea whilst swallowing a bolus of food.
What changes occur in the trachea of a heavy smoker?
Stratified squamous metaplasia
What are the cells of the respiratory epithelium?
Ciliated columnar cells - motile cilia sweep particulate matter through mucous, upwards to it can be coughed up or swallowed
Goblet cells - secrete mucous
Basal cells - step cells that can differentiate into other respiratory epitheium cells ininjury
Brush cells - chemmo- and general sensory cells
Granule cells - endocrine cells
What are the differences between the L and R primary bronchi? What is the significance of this?
R is wider and descends more steeply. Also, as the carina is located slightly left of midline, this means aspirated objects are more likely to end up in the R lung
What is the carina?
Cartilagenous ridge at the bifurcation of the trachea. Located slightly left of midline at the T4/5 plane
How many primary bronchi are there on the L and R?
2 on the left (upper and lower lobes) and 3 on the right (upper, middle and lower lobes)
How many tertiary bronchioles in the L and R lungs? What do they supply?
Supply bronchopulmonary segments.
Right: 10
3 to the upper lobe, 2 to the middle lobe, 5 to the lower lobe.
LEft: 8-10
4-5 to the upper, 4-5 to the lower.
What shape is a bronchopulmonary segment? Significane?
cone/wedge shape.
Each is supplied by a bronchopulmonary artery. If there is a PE etc, in one of these, the result is a wedge shaped infarct.
When are bronchi considered bronchioles?
When they becomes 1mm or less in diameter
What is a lobule? What airway segment supplies it?
Lobule is a hexagonal segment that constitutes the smallest visible division of the lungs. Supplied by a terminal bronchiole.
Changes to epithelium within the bronchi
Bronchi are originally histologically identical to the trachea. As they enter the lungs, they begin to change. With decreasing airway diameter there is a:
Gradual reduction in epithelial cell height
Less continuous hyaline cartilage
Few goblet cells
Fewer submucosal glands
The originally thick basement membrane of the trachea becomes thinner
Changes to the epithelium from the bronchioles to the respiratory bronchioles.
In the bronchioles:
Gradually decreasing epithelial cell hight, presence of clara cells begins.
Terminal Bronchioles:
Simple cuboidal epithelium
Respiratory Bronchioles:
Simple Cuboidal Epithelium interrupted by alveoli
Changes in smooth muscle from bronchi to respiratory bronchioles
Bronchi: ‘Muscalaris’ layer of the bronchial wall is continuous, becomes slightly less so
Bronchioles: Relatively thick smooth muscle layer, compared to their size
Respiratory: Knobs of muscle occasionally present, w/ simple cuboidal epithelium covering them. More proximally this epithelium is ciliated cuboidal cells and clara cells. More distaly, becomes mainly clara cells.
CHages in goblet cells from bronchi to bronchioles
Gradually decreasing numbers of goblet cells as bronchial diameter decreases,
Gradually replaced by clara cells in bronchioles, then disappear
CHanges in the cartilage from bronchi to bronchioles
Within bronchi, becomes less continuous, develop cartilage ‘plates’
No cartilage plates in bronchi, but occasional elements of cartilages at branchings
How does a respiratory bronchiole differ from a terminal bronchiole
Terminal bronchioles and respiratory bronchioles both have a simple cuboidal epithelium. Respiratory bronchioles have more clara cells. Alveoli interrupt the walls of respiratory bronchioles, but are not present in terminal bronchioles.
Terminal bronchioles = the last division of the conducting airways, and Respiratory bronchioles = the first of the respiratory zone
